{"id":696,"date":"2021-12-17T21:51:16","date_gmt":"2021-12-17T21:51:16","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/10-mass-wasting\/"},"modified":"2025-01-21T01:03:29","modified_gmt":"2025-01-21T01:03:29","slug":"10-mass-wasting","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/10-mass-wasting\/","title":{"raw":"10 Mass Wasting","rendered":"10 Mass Wasting"},"content":{"raw":"[caption id=\"attachment_3390\" align=\"aligncenter\" width=\"800\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/Thistlelandslideusgs.jpg\"><img class=\"size-full wp-image-669\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs.jpg\" alt=\"The 1983 Thistle landslide (foreground) dammed the Spanish Fork river creating a lake.\" width=\"800\" height=\"543\"><\/a> The 1983 Thistle landslide (foreground) dammed the Spanish Fork River creating a lake that covered the town of Thistle, Utah. The slide covered Hwy 6 and the main railroad between Salt Lake and Denver.[\/caption]\n<h1>10 Mass Wasting<\/h1>\n<b>KEY CONCEPTS<\/b>\n\n<b>At the end of this chapter, students should be able to:<\/b>\n<ul>\n \t<li>Explain what [pb_glossary id=\"3110\"]mass wasting[\/pb_glossary] is and why it occurs on a slope<\/li>\n \t<li>Explain the basic triggers of mass-wasting events and how they occur<\/li>\n \t<li>Identify types of [pb_glossary id=\"3110\"]mass wasting[\/pb_glossary]<\/li>\n \t<li>Identify risk factors for mass-wasting events<\/li>\n \t<li>Evaluate [pb_glossary id=\"1199\"]landslides[\/pb_glossary] and their contributing factors<\/li>\n<\/ul>\nThis chapter discusses the fundamental processes driving mass-wasting, types of [pb_glossary id=\"3110\"]mass wasting[\/pb_glossary], examples and lessons learned from famous mass-wasting events, how [pb_glossary id=\"3110\"]mass wasting[\/pb_glossary] can be predicted, and how people can be protected from this potential hazard. <strong>[pb_glossary id=\"3110\"]Mass wasting[\/pb_glossary]<\/strong> is the downhill movement of rock and [pb_glossary id=\"1203\"]soil[\/pb_glossary] material due to gravity. The term [pb_glossary id=\"1199\"]landslide[\/pb_glossary] is often used as a synonym for [pb_glossary id=\"3110\"]mass wasting[\/pb_glossary], but [pb_glossary id=\"3110\"]mass wasting[\/pb_glossary] is a much broader term referring to all movement downslope. Geologically, [pb_glossary id=\"1199\"]landslide[\/pb_glossary] is a general term for [pb_glossary id=\"3110\"]mass wasting[\/pb_glossary] that involves fast-moving geologic material. Loose material along with overlying [pb_glossary id=\"1203\"]soils[\/pb_glossary] are what typically move during a mass-wasting event. Moving blocks of [pb_glossary id=\"1971\"]bedrock[\/pb_glossary] are called rock topples, rock slides, or rock [pb_glossary id=\"3119\"]falls[\/pb_glossary], depending on the dominant motion of the blocks. Movements of dominantly liquid material are called flows. Movement by [pb_glossary id=\"3110\"]mass wasting[\/pb_glossary] can be slow or rapid. Rapid movement can be dangerous, such as during [pb_glossary id=\"3123\"]debris flows[\/pb_glossary]. Areas with steep topography and rapid rainfall, such as the California [pb_glossary id=\"2890\"]coast[\/pb_glossary], Rocky Mountain Region, and Pacific Northwest, are particularly susceptible to hazardous mass-wasting events.\n<h2><span style=\"font-weight: 400\">10.1 Slope Strength<\/span><\/h2>\n[caption id=\"attachment_3391\" align=\"alignright\" width=\"359\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.1_Block_on_Incline.png\"><img class=\"wp-image-670\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Block_on_Incline.png\" alt=\"Forces on a block on an inclined plane (fg = force of gravity; fn = normal force; fs = shear force).\" width=\"359\" height=\"188\"><\/a> Forces on a block on an inclined plane (fg = force of gravity; fn = normal force; fs = shear force).[\/caption]\n\n[pb_glossary id=\"3110\"]Mass wasting[\/pb_glossary] occurs when a slope fails. A slope fails when it is too steep and unstable for existing materials and conditions. Slope stability is ultimately determined by two principal factors: the slope angle and the strength of the underlying material. Force of gravity, which plays a part in [pb_glossary id=\"3110\"]mass wasting[\/pb_glossary], is constant on the Earth\u2019s surface for the most part, although small variations exist depending on the elevation and density of the underlying rock. In the figure, a block of rock situated on a slope is pulled down toward the Earth\u2019s center by the force of gravity (fg). The gravitational force acting on a slope can be divided into two components: the [pb_glossary id=\"1447\"]shear[\/pb_glossary] or [pb_glossary id=\"3112\"]driving force[\/pb_glossary] (fs) pushing the block down the slope, and the normal or [pb_glossary id=\"3113\"]resisting force[\/pb_glossary] (fn) pushing into the slope, which produces friction. The relationship between [pb_glossary id=\"3112\"]shear force[\/pb_glossary] and [pb_glossary id=\"3113\"]normal force[\/pb_glossary] is called [pb_glossary id=\"3114\"]shear strength[\/pb_glossary]. When the normal force, i.e., friction, is greater than the [pb_glossary id=\"3112\"]shear force[\/pb_glossary], then the block does <em>not <\/em>move downslope. However, if the slope angle becomes steeper or if the earth material is weakened, [pb_glossary id=\"3112\"]shear force[\/pb_glossary] exceeds [pb_glossary id=\"3113\"]normal force[\/pb_glossary], compromising [pb_glossary id=\"3114\"]shear strength[\/pb_glossary], and downslope movement occurs.\n\n[caption id=\"attachment_3392\" align=\"aligncenter\" width=\"1024\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.1_blocks-on-incline.png\"><img class=\"size-large wp-image-671\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_blocks-on-incline-1024x291.png\" alt=\"As slope increases, the force of gravity (fg) stays the same and the normal force decreases while the shear force proportionately increases.\" width=\"1024\" height=\"291\"><\/a> As slope increases, the force of gravity (fg) stays the same and the normal force decreases while the shear force proportionately increases.[\/caption]\n\nIn the figure, the force vectors change as the slope angle increases. The gravitational force doesn\u2019t change, but the [pb_glossary id=\"3112\"]shear force[\/pb_glossary] increases while the [pb_glossary id=\"3113\"]normal force[\/pb_glossary] decreases. The steepest angle at which rock and [pb_glossary id=\"1203\"]soil[\/pb_glossary] material is stable and will <em>not<\/em> move downslope is called the <strong>[pb_glossary id=\"3115\"]angle of repose[\/pb_glossary].<\/strong> The [pb_glossary id=\"3115\"]angle of repose[\/pb_glossary] is measured relative from the horizontal. When a slope is at the [pb_glossary id=\"3115\"]angle of repose[\/pb_glossary], the [pb_glossary id=\"3112\"]shear force[\/pb_glossary] is in equilibrium with the [pb_glossary id=\"3113\"]normal force[\/pb_glossary]. If the slope becomes just slightly steeper, the [pb_glossary id=\"3112\"]shear force[\/pb_glossary] exceeds the [pb_glossary id=\"3113\"]normal force[\/pb_glossary], and the material starts to move downhill. The [pb_glossary id=\"3115\"]angle of repose[\/pb_glossary] varies for all material and slopes depending on many factors such as [pb_glossary id=\"2828\"]grain size[\/pb_glossary], grain [pb_glossary id=\"2831\"]composition[\/pb_glossary], and water content. The figure shows the [pb_glossary id=\"3115\"]angle of repose[\/pb_glossary] for sand that is poured into a pile on a flat surface. The sand grains cascade down the sides of the pile until coming to rest at the [pb_glossary id=\"3115\"]angle of repose[\/pb_glossary]. At that angle, the base and height of the pile continue to increase, but the angle of the sides remains the same.<span style=\"font-weight: 400\">\u00a0<\/span>\n\n[caption id=\"attachment_3393\" align=\"alignleft\" width=\"300\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.1_Angleofrepose.png\"><img class=\"wp-image-672 size-medium\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Angleofrepose-300x167.png\" alt=\"Angle of repose in a pile of sand.\" width=\"300\" height=\"167\"><\/a> Angle of repose in a pile of sand.[\/caption]\n\nWater is a common factor that can significantly change the [pb_glossary id=\"3114\"]shear strength[\/pb_glossary] of a particular slope. Water is located in <strong>[pb_glossary id=\"3116\"]pore[\/pb_glossary] spaces<\/strong>, which are empty air spaces in [pb_glossary id=\"2678\"]sediments[\/pb_glossary] or rocks between the grains. For example, assume a dry sand pile has an [pb_glossary id=\"3115\"]angle of repose[\/pb_glossary] of 30 degrees. If water is added to the sand, the [pb_glossary id=\"3115\"]angle of repose[\/pb_glossary] will increase, possibly to 60 degrees or even 90 degrees, such as a sandcastle being built at a beach. But if too much water is added to the pore spaces of the sandcastle, the water decreases the [pb_glossary id=\"3114\"]shear strength[\/pb_glossary], lowers the [pb_glossary id=\"3115\"]angle of repose[\/pb_glossary], and the sandcastle collapses.\n\nAnother factor influencing [pb_glossary id=\"3114\"]shear strength[\/pb_glossary] are planes of weakness in sedimentary rocks. [pb_glossary id=\"2857\"]Bedding[\/pb_glossary] planes (<a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/5-weathering-erosion-and-sedimentary-rocks\/\">see Chapter 5<\/a>) can act as significant planes of weakness when they are parallel to the slope but less so if they are perpendicular to the slope. At locations A and B, the [pb_glossary id=\"2857\"]bedding[\/pb_glossary] is nearly perpendicular to the slope and relatively stable. At location D, the [pb_glossary id=\"2857\"]bedding[\/pb_glossary] is nearly parallel to the slope and quite unstable. At location C, the [pb_glossary id=\"2857\"]bedding[\/pb_glossary] is nearly horizontal, and the stability is [pb_glossary id=\"1955\"]intermediate[\/pb_glossary] between the other two extremes [1]. Additionally, if clay [pb_glossary id=\"3375\"]minerals[\/pb_glossary] form along [pb_glossary id=\"2857\"]bedding[\/pb_glossary] planes, they can absorb water and become slick. When a [pb_glossary id=\"2857\"]bedding[\/pb_glossary] plane of [pb_glossary id=\"2839\"]shale[\/pb_glossary] (clay and silt) becomes [pb_glossary id=\"2706\"]saturated[\/pb_glossary], it can lower the [pb_glossary id=\"3114\"]shear strength[\/pb_glossary] of the rock mass and cause a [pb_glossary id=\"1199\"]landslide[\/pb_glossary], such as at the 1925 Gros Ventre, Wyoming rock slide. See the case studies section for details on this and other [pb_glossary id=\"1199\"]landslides[\/pb_glossary].\n\n[caption id=\"attachment_3394\" align=\"aligncenter\" width=\"1024\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses.png\"><img class=\"size-large wp-image-673\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses-1024x356.png\" alt=\"At locations A and B, the bedding is nearly perpendicular to the slope and the bedding is relatively stable. At location D, the bedding is nearly parallel to the slope and the bedding is quite unstable. At location C the bedding is nearly horizontal and the stability is intermediate between the other two extremes.\" width=\"1024\" height=\"356\"><\/a> Locations A and B have bedding nearly perpendicular to the slope, making for a relatively stable slope. Location D has bedding nearly parallel to the slope, increasing the risk of slope failure. Location C has bedding nearly horizontal and the stability is relatively intermediate.[\/caption]\n<h3>Take this quiz to check your comprehension of this section.<\/h3>\n[h5p id=\"67\"]\n\n[caption id=\"attachment_4398\" align=\"aligncenter\" width=\"150\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10.1-Did-I-Get-It-QR-Code.png\"><img class=\"wp-image-674 size-thumbnail\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1-Did-I-Get-It-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\"><\/a> If you are using the printed version of this OER, access the quiz for section 10.1 via this QR Code.[\/caption]\n<h2><span style=\"font-weight: 400\">10.2 Mass-Wasting Triggers &amp; Mitigation\n<\/span><\/h2>\nMass-wasting events often have a <strong>[pb_glossary id=\"3117\"]trigger[\/pb_glossary]<\/strong>: something changes that causes a [pb_glossary id=\"1199\"]landslide[\/pb_glossary] to occur at a specific time. It could be rapid snowmelt, intense rainfall, earthquake shaking, [pb_glossary id=\"1181\"]volcanic[\/pb_glossary] eruption, storm waves, rapid-[pb_glossary id=\"3134\"]stream[\/pb_glossary] [pb_glossary id=\"2677\"]erosion[\/pb_glossary], or human activities, such as [pb_glossary id=\"2862\"]grading[\/pb_glossary] a new road. Increased water content within the slope is the most common mass-wasting [pb_glossary id=\"3117\"]trigger[\/pb_glossary]. Water content can increase due to rapidly melting snow or ice or an intense rain event. Intense rain events can occur more often during El Ni\u00f1o years. Then, the west [pb_glossary id=\"2890\"]coast[\/pb_glossary] of North America receives more [pb_glossary id=\"2707\"]precipitation[\/pb_glossary] than normal, and [pb_glossary id=\"1199\"]landslides[\/pb_glossary] become more common. Changes in surface-water conditions resulting from earthquakes, previous slope failures that dam up [pb_glossary id=\"3134\"]streams[\/pb_glossary], or human structures that interfere with [pb_glossary id=\"3127\"]runoff[\/pb_glossary], such as \u00a0buildings, roads, or parking lots can provide additional water to a slope. In the case of the 1959 Hebgen Lake rock slide, Madison Canyon, Montana, the [pb_glossary id=\"3114\"]shear strength[\/pb_glossary] of the slope may have been weakened by earthquake shaking. Most [pb_glossary id=\"1199\"]landslide[\/pb_glossary] mitigation diverts and drains water away from slide areas.\u00a0 Tarps and plastic sheeting\u00a0 are often used to drain water off of slide bodies and prevent [pb_glossary id=\"3128\"]infiltration[\/pb_glossary] into the slide. Drains are used to dewater [pb_glossary id=\"1199\"]landslides[\/pb_glossary] and shallow wells are used to monitor the water content of some active [pb_glossary id=\"1199\"]landslides[\/pb_glossary].\n\nAn <strong>[pb_glossary id=\"3118\"]oversteepened[\/pb_glossary]<\/strong> slope may also [pb_glossary id=\"3117\"]trigger[\/pb_glossary] [pb_glossary id=\"1199\"]landslides[\/pb_glossary]. Slopes can be made excessively steep by natural processes of [pb_glossary id=\"2677\"]erosion[\/pb_glossary] or when humans modify the landscape for building construction. An example of how a slope may be [pb_glossary id=\"3118\"]oversteepened[\/pb_glossary] during development occurs where the bottom of the slope is cut into, perhaps to build a road or level a building lot, and the top of the slope is modified by depositing excavated material from below. If done carefully, this practice can be very useful in land development, but in some cases, this can result in devastating consequences. For example, this might have been a contributing factor in the 2014 North Salt Lake City, Utah [pb_glossary id=\"1199\"]landslide[\/pb_glossary]. A former gravel pit was regraded to provide a road and several building lots. These activities may have [pb_glossary id=\"3118\"]oversteepened[\/pb_glossary] the slope, which resulted in a slow moving [pb_glossary id=\"1199\"]landslide[\/pb_glossary] that destroyed one home at the bottom of the slope. Natural processes such as excessive [pb_glossary id=\"3134\"]stream[\/pb_glossary] [pb_glossary id=\"2677\"]erosion[\/pb_glossary] from a flood or coastal erosion during a storm can also [pb_glossary id=\"3118\"]oversteepen[\/pb_glossary] slopes. For example, natural undercutting of the riverbank was proposed as part of the [pb_glossary id=\"3117\"]trigger[\/pb_glossary] for the famous 1925 Gros Ventre, Wyoming rock slide.\n\nSlope reinforcement can help prevent and mitigate [pb_glossary id=\"1199\"]landslides[\/pb_glossary] .\u00a0 For [pb_glossary id=\"3119\"]rockfall[\/pb_glossary]-prone areas, sometimes it is economical to use long steel bolts. Bolts, drilled a few meters into a rock face, can secure loose pieces of material that could pose a hazard. Shockcrete, a reinforced spray-on form of concrete, can strengthen a slope face when applied properly. Buttressing a slide by adding weight at the toe of the slide and removing weight from the head of the slide, can stabilize a [pb_glossary id=\"1199\"]landslide[\/pb_glossary].\u00a0 Terracing, which creates a stairstep topography, can be applied to help with slope stabilization, but it must be applied at the proper scale to be effective.\n\nA different approach in reducing [pb_glossary id=\"1199\"]landslide[\/pb_glossary] hazard is to [pb_glossary id=\"2207\"]shield[\/pb_glossary], catch, and divert the runout material.\u00a0 Sometimes the most economical way to deal with a [pb_glossary id=\"1199\"]landslide[\/pb_glossary] hazard is to divert and slow the falling material.\u00a0 Special stretchable fencing can be applied in areas where [pb_glossary id=\"3119\"]rockfall[\/pb_glossary] is common to protect pedestrians and vehicles.\u00a0 Runout channels, diversion structures, and check dams can be used to slow [pb_glossary id=\"3123\"]debris flows[\/pb_glossary] and divert them around structures.\u00a0 Some highways have special tunnels that divert [pb_glossary id=\"1199\"]landslides[\/pb_glossary] over the highway.\u00a0 In all of these cases the shielding has to be engineered to a scale that is greater than the slide, or catastrophic loss in property and life could result.\n<h3>Take this quiz to check your comprehension of this section.<\/h3>\n[h5p id=\"68\"]\n\n[caption id=\"attachment_4399\" align=\"aligncenter\" width=\"150\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10.2-Did-I-Get-It-QR-Code.png\"><img class=\"size-thumbnail wp-image-675\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.2-Did-I-Get-It-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\"><\/a> If you are using the printed version of this OER, access the quiz for section 10.2 via this QR Code.[\/caption]\n<h2><span style=\"font-weight: 400\">10.3 Landslide Classification &amp; Identification\n<\/span><\/h2>\nMass-wasting events are classified by type of movement and type of material, and there are several ways to classify these events. The figure and table show terms used. In addition, mass-wasting types often share common morphological features observed on the surface, such as the head scarp\u2014commonly seen as crescent shapes on a cliff face; hummocky or uneven surfaces; accumulations of [pb_glossary id=\"3370\"]talus[\/pb_glossary]\u2014loose rocky material falling from above; and toe of slope, which covers existing surface material. <code><\/code>\n<h3><strong>10.3.1 Types of Mass Wasting<\/strong><\/h3>\nThe most common mass-wasting types are [pb_glossary id=\"3119\"]falls[\/pb_glossary], rotational and [pb_glossary id=\"3121\"]translational slides[\/pb_glossary], flows, and [pb_glossary id=\"2447\"]creep[\/pb_glossary]. <strong>[pb_glossary id=\"3119\"]Falls[\/pb_glossary]<\/strong> are abrupt rock movements that detach from steep slopes or cliffs. Rocks separate along existing natural breaks such as [pb_glossary id=\"1934\"]fractures[\/pb_glossary] or [pb_glossary id=\"2857\"]bedding[\/pb_glossary] planes. Movement occurs as free-falling, bouncing, and rolling. [pb_glossary id=\"3119\"]Falls[\/pb_glossary] are strongly influenced by gravity, [pb_glossary id=\"1204\"]mechanical weathering[\/pb_glossary], and water. <strong>[pb_glossary id=\"3120\"]Rotational slides[\/pb_glossary]<\/strong> commonly show slow movement along a curved rupture surface. <strong>[pb_glossary id=\"3121\"]Translational slides[\/pb_glossary]<\/strong> often are rapid movements along a plane of distinct weakness between the overlying slide material and more stable underlying material. Slides can be further subdivided into rock slides, debris slides, or earth slides depending on the type of the material involved (see table).\n<table class=\" aligncenter\" style=\"width: 100%;border-style: none;border-color: #000000\"><caption><span style=\"font-size: 10pt\"><em>Table of [pb_glossary id=\"3110\"]<em>Mass Wasting<\/em>[\/pb_glossary] Types. \u00a0[pb_glossary id=\"3110\"]<em>Mass wasting<\/em>[\/pb_glossary] movement type and primary earth material. Modified from [zotpressInText item=\"{948446:KG8X6AAJ},{948446:HN9CI37K}\" format=\"(%num%)\" brackets=\"yes\"].<\/em><\/span><\/caption>\n<tbody>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\" rowspan=\"3\">&nbsp;\n\n<b>Type of Movement<\/b><\/td>\n<td style=\"width: 76.4277%;background-color: #68e88a;border-color: #000000;text-align: center\" colspan=\"3\"><b>Primary Material Type and Common Name of Slide<\/b><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 26.61%;background-color: #68e88a;border-color: #000000;text-align: center\" rowspan=\"2\"><b>[pb_glossary id=\"1971\"]Bedrock[\/pb_glossary]<\/b><\/td>\n<td style=\"width: 49.8177%;background-color: #68e88a;border-color: #000000;text-align: center\" colspan=\"2\"><b>[pb_glossary id=\"1203\"]Soil[\/pb_glossary] Types<\/b><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 24.9089%;background-color: #68e88a;border-color: #000000;text-align: center\"><b>Mostly Coarse-Grained<\/b><\/td>\n<td style=\"width: 24.9089%;background-color: #68e88a;border-color: #000000;text-align: center\"><b>Mostly Fine-Grained<\/b><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b>[pb_glossary id=\"3119\"]Falls[\/pb_glossary]<\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">[pb_glossary id=\"3119\"]Rock Fall[\/pb_glossary]<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">---<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">---<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b>Rock Avalanche<\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Rock Avalanche<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">---<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">---<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b>[pb_glossary id=\"3120\"]Rotational Slide[\/pb_glossary] (Slump)<\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">---<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Rotational Debris Slide (Slump)<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Rotational Earth Slide (Slump)<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b>[pb_glossary id=\"3121\"]Translational Slide[\/pb_glossary]<\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Translational Rock Slide<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Translational Debris Slide<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Translational Earth Slide<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b>Flows<\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">---<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">[pb_glossary id=\"3123\"]Debris Flow[\/pb_glossary]<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">[pb_glossary id=\"3124\"]Earth flow[\/pb_glossary]<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b>[pb_glossary id=\"3125\"]Soil Creep[\/pb_glossary]<\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">---<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">[pb_glossary id=\"2447\"]Creep[\/pb_glossary]<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">[pb_glossary id=\"2447\"]Creep[\/pb_glossary]<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<em><span style=\"font-weight: 400\">\u00a0<\/span><\/em>\n\n[caption id=\"attachment_3395\" align=\"aligncenter\" width=\"548\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.3_Fig3grouping-2LG.jpg\"><img class=\"size-full wp-image-676\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3_Fig3grouping-2LG.jpg\" alt=\"Examples of some of the types of landslides.\" width=\"548\" height=\"663\"><\/a> Examples of some of the types of landslides.[\/caption]\n\nFlows are rapidly moving mass-wasting events in which the loose material is typically mixed with abundant water, creating long runouts at the slope base. Flows are commonly separated into <b>[pb_glossary id=\"3123\"]debris flow[\/pb_glossary]<\/b> (coarse material)\u00a0and <b>[pb_glossary id=\"3124\"]earthflow[\/pb_glossary]<\/b> (fine material) depending on the type of material involved and the amount of water. Some of the largest and fastest flows on land are called <strong>[pb_glossary id=\"3122\"]sturzstroms[\/pb_glossary]<\/strong>, or long runout [pb_glossary id=\"1199\"]landslides[\/pb_glossary]. They are still poorly understood, but are known to travel for long distances, even in places without significant atmospheres like the Moon.\n\n<b>[pb_glossary id=\"2447\"]Creep[\/pb_glossary]<\/b> is the imperceptibly slow downward movement of material caused by a regular cycle of nighttime freezing followed by daytime thawing in unconsolidated material such as [pb_glossary id=\"1203\"]soil[\/pb_glossary]. During the freeze, expansion of ice pushes [pb_glossary id=\"1203\"]soil[\/pb_glossary] particles out away from the slope, while the next day following the thaw, gravity pulls them directly downward. The net effect is a gradual movement of surface [pb_glossary id=\"1203\"]soil[\/pb_glossary] particles downhill. [pb_glossary id=\"2447\"]Creep[\/pb_glossary] is indicated by curved tree trunks, bent fences or retaining walls, tilted poles or fences, and small [pb_glossary id=\"1203\"]soil[\/pb_glossary] [pb_glossary id=\"2868\"]ripples[\/pb_glossary] or ridges. A special type of [pb_glossary id=\"3125\"]soil creep[\/pb_glossary] is solifluction, which is the slow movement of [pb_glossary id=\"1203\"]soil[\/pb_glossary] lobes on low-angle slopes due to [pb_glossary id=\"1203\"]soil[\/pb_glossary] seasonally freezing and thawing in high-[pb_glossary id=\"3372\"]latitude[\/pb_glossary], typically sub-Arctic, Arctic, and Antarctic locations.\n\n&nbsp;\n<figure>\n\n[caption id=\"attachment_4404\" align=\"alignleft\" width=\"150\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/Landslide-Hazards-Youtube-QR-Code.png\"><img class=\"size-thumbnail wp-image-677\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/Landslide-Hazards-Youtube-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\"><\/a> If you are using the printed version of this OER, access this YouTube video via this QR Code.[\/caption]\n\n[embed]https:\/\/www.youtube.com\/embed\/MVwSpGVfWVo[\/embed]\n\n<span style=\"font-size: 10pt;color: #333333\"><em>[pb_glossary id=\"1199\"]<em>Landslide<\/em>[\/pb_glossary] Hazards, David Applegate<\/em><\/span>\n<h3><strong>10.3.2 Parts of a Landslide<\/strong><\/h3>\n[pb_glossary id=\"1199\"]Landslides[\/pb_glossary] have several identifying features that can be common across the different types of [pb_glossary id=\"3110\"]mass wasting[\/pb_glossary]. Note that there are many exceptions, and a [pb_glossary id=\"1199\"]landslide[\/pb_glossary] does not have to have these features. Displacement of material by [pb_glossary id=\"1199\"]landslides[\/pb_glossary] causes the absence of material uphill and the [pb_glossary id=\"2679\"]deposition[\/pb_glossary] of new material downhill, and careful [pb_glossary id=\"2651\"]observation[\/pb_glossary] can identify the evidence of that displacement. Other signs of [pb_glossary id=\"1199\"]landslides[\/pb_glossary] include tilted or [pb_glossary id=\"3081\"]offset[\/pb_glossary] structures or natural features that would normally be vertical or in place.\nMany [pb_glossary id=\"1199\"]landslides[\/pb_glossary] have escarpments or scarps. [pb_glossary id=\"1199\"]Landslide[\/pb_glossary] scarps, like [pb_glossary id=\"3107\"]fault scarps[\/pb_glossary], are steep terrain created when movement of the adjacent land exposes a part of the subsurface. The most prominent scarp is the main scarp, which marks the uphill extent of the [pb_glossary id=\"1199\"]landslide[\/pb_glossary]. As the disturbed material moves out of place, a step slope forms and develops a new hillside escarpment for the undisturbed material. Main scarps are formed by movement of the displaced material away from the undisturbed ground and are the visible part of slide rupture surface.\n\n&nbsp;\n\n[h5p id=\"69\"]\n\n[caption id=\"attachment_4401\" align=\"aligncenter\" width=\"150\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10.3-Rotational-Landslide-QR-Code.png\"><img class=\"size-thumbnail wp-image-678\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Rotational-Landslide-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\"><\/a> If you are using the printed version of this OER, access this interactive activity via this QR Code.[\/caption]\n\nThe slide rupture surface is the boundary of the body of movement of the [pb_glossary id=\"1199\"]landslide[\/pb_glossary]. The geologic material below the slide surface does not move, and is marked on the sides by the flanks of the [pb_glossary id=\"1199\"]landslide[\/pb_glossary] and at the end by the toe of the [pb_glossary id=\"1199\"]landslide[\/pb_glossary].\n\nThe toe of the [pb_glossary id=\"1199\"]landslide[\/pb_glossary] marks the end of the moving material. The toe marks the runout, or maximum distance traveled, of the [pb_glossary id=\"1199\"]landslide[\/pb_glossary]. In rotational [pb_glossary id=\"1199\"]landslides[\/pb_glossary], the toe is often a large, disturbed mound of geologic material, forming as the [pb_glossary id=\"1199\"]landslide[\/pb_glossary] moves past its original rupture surface.\n\nRotational and translational [pb_glossary id=\"1199\"]landslides[\/pb_glossary] often have [pb_glossary id=\"1445\"]extensional[\/pb_glossary] cracks, sag ponds, hummocky terrain and pressure ridges. [pb_glossary id=\"1445\"]Extensional[\/pb_glossary] cracks form when a [pb_glossary id=\"1199\"]landslide[\/pb_glossary]\u2019s toe moves forward faster than the rest of [pb_glossary id=\"1199\"]landslide[\/pb_glossary], resulting in [pb_glossary id=\"1445\"]tensional[\/pb_glossary] forces. Sag ponds are small bodies of water filling depressions formed where [pb_glossary id=\"1199\"]landslide[\/pb_glossary] movement has impounded [pb_glossary id=\"3130\"]drainage[\/pb_glossary]. Hummocky terrain is undulating and uneven topography that results from the ground being disturbed. Pressure ridges develop on the margins of the [pb_glossary id=\"1199\"]landslide[\/pb_glossary] where material is forced upward into a ridge structure.\n<h3>Take this quiz to check your comprehension of this section.<\/h3>\n[h5p id=\"70\"]\n\n[caption id=\"attachment_4434\" align=\"aligncenter\" width=\"150\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10..3-Did-I-Get-It-QR-Code.png\"><img class=\"size-thumbnail wp-image-679\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Did-I-Get-It-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\"><\/a> If you are using the printed version of this OER, access the quiz for section 10.3 via this QR Code.[\/caption]\n<h2><span style=\"font-weight: 400\">10.4 Examples of Landslides<\/span><\/h2>\n<h4><span style=\"font-weight: 400\">Landslides in United States<\/span><\/h4>\n[caption id=\"attachment_3396\" align=\"aligncenter\" width=\"444\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/DSC_0048-1.jpg\"><img class=\"wp-image-680\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0048-1-300x200.jpg\" alt=\"Scar of the Gros Ventre landslide in background with landslide deposits in the foreground.\" width=\"444\" height=\"296\"><\/a> Scar of the Gros Ventre landslide in background with landslide deposits in the foreground.[\/caption]\n\n<b>1925, Gros Ventre, Wyoming:<\/b><span style=\"font-weight: 400\"> On June 23, 1925, a 38 million cubic meter (50 million cu yd) translational rock slide occurred next to the Gros Ventre [pb_glossary id=\"3134\"]River[\/pb_glossary] (pronounced \u201cgrow vont\u201d) near Jackson Hole, Wyoming. Large boulders dammed the Gros Ventre [pb_glossary id=\"3134\"]River[\/pb_glossary] and ran up the opposite side of the valley several hundred vertical feet. The dammed [pb_glossary id=\"3134\"]river[\/pb_glossary] created Slide Lake, and two years later in 1927, lake levels rose high enough to destabilize the dam. The dam failed and caused a catastrophic flood that killed six people in the small downstream community of Kelly, Wyoming. <\/span>\n\n[caption id=\"attachment_3397\" align=\"aligncenter\" width=\"550\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.4_Gros_Ventre-Cross-section.jpg\"><img class=\"wp-image-681 size-full\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Gros_Ventre-Cross-section.jpg\" alt=\"Shows a before and after scenario of the Gros Ventre slide area with bedding parallel to the surface and oversteepending caused by the river. The &quot;after&quot; image show how the rock material slide along a bedding plane.\" width=\"550\" height=\"349\"><\/a> Cross-section of 1925 Gros Ventre slide showing sedimentary layers parallel with the surface and undercutting (oversteepening) of the slope by the river.[\/caption]\n\n<span style=\"font-weight: 400\">A combination of three factors caused the rock slide: 1) heavy rains and rapidly melting snow [pb_glossary id=\"2706\"]saturated[\/pb_glossary] the Tensleep [pb_glossary id=\"2834\"]Sandstone[\/pb_glossary] causing the underlying [pb_glossary id=\"2839\"]shale[\/pb_glossary] of the Amsden [pb_glossary id=\"2960\"]Formation[\/pb_glossary] to lose its [pb_glossary id=\"3114\"]shear strength[\/pb_glossary], 2) the Gros Ventre [pb_glossary id=\"3134\"]River[\/pb_glossary] cut through the [pb_glossary id=\"2834\"]sandstone[\/pb_glossary] creating an [pb_glossary id=\"3118\"]oversteepened[\/pb_glossary] slope, and 3) soil on top of the mountain became saturated with water due to poor [pb_glossary id=\"3130\"]drainage[\/pb_glossary]. <\/span><span style=\"font-weight: 400\">The cross-section diagram shows how the parallel [pb_glossary id=\"2857\"]bedding[\/pb_glossary] planes between the Tensleep [pb_glossary id=\"2834\"]Sandstone[\/pb_glossary] and Amsden [pb_glossary id=\"2960\"]Formation[\/pb_glossary] offered little friction against the slope surface as the [pb_glossary id=\"3134\"]river[\/pb_glossary] undercut the [pb_glossary id=\"2834\"]sandstone[\/pb_glossary]. Lastly, the rockslide may have been triggered by an earthquake.\n<\/span>\n\n<b>1959, Madison Canyon, Montana:<\/b><span style=\"font-weight: 400\"> In 1959, the largest earthquake in Rocky Mountain recorded history, [pb_glossary id=\"3098\"]magnitude[\/pb_glossary] 7.5, struck the Hebgen Lake, Montana area, causing a destructive seiche on the lake (see <a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/9-crustal-deformation-and-earthquakes\/\">Chapter 9<\/a>). The earthquake caused a rock avalanche that dammed the Madison [pb_glossary id=\"3134\"]River[\/pb_glossary], creating Quake Lake, and ran up the other side of the valley hundreds of vertical feet. Today, there are still house-sized boulders visible on the slope opposite their starting point. The slide moved at a velocity of up to 160.9 kph (100 mph), creating an incredible air blast that swept through the Rock Creek Campground. The slide killed 28 people, most of whom were in the campground and remain buried there. In a manner like the Gros Ventre slide, [pb_glossary id=\"2924\"]foliation[\/pb_glossary] planes of weakness in [pb_glossary id=\"2684\"]metamorphic rock[\/pb_glossary] outcrops were parallel with the surface, compromising [pb_glossary id=\"3114\"]shear strength[\/pb_glossary].<\/span>\n\n[caption id=\"attachment_3398\" align=\"aligncenter\" width=\"1024\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/DSC_0445-DSC_0454_blended_fused-e1491189091595.png\"><img class=\"size-large wp-image-682\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0445-DSC_0454_blended_fused-e1491189091595-1024x361.png\" alt=\"1959 Madison Canyon landslide scar. Photo taken from landslide material.\" width=\"1024\" height=\"361\"><\/a> 1959 Madison Canyon landslide scar. Photo taken from landslide material.[\/caption]\n\n<strong>1980, Mount Saint Helens, Washington<\/strong>: On May 18, 1980 a 5.1-[pb_glossary id=\"3098\"]magnitude[\/pb_glossary] earthquake triggered the largest [pb_glossary id=\"1199\"]landslide[\/pb_glossary] observed in the historical record.\u00a0 This [pb_glossary id=\"1199\"]landslide[\/pb_glossary] was followed by the lateral eruption of Mount Saint Helens [pb_glossary id=\"1181\"]volcano[\/pb_glossary], and the eruption was followed by [pb_glossary id=\"1181\"]volcanic[\/pb_glossary] [pb_glossary id=\"3123\"]debris flows[\/pb_glossary] known as [pb_glossary id=\"1201\"]lahars[\/pb_glossary]. The volume of material moved by the [pb_glossary id=\"1199\"]landslide[\/pb_glossary] was 2.8 cubic kilometers (0.67 mi<sup>3<\/sup>).\n\n<b>1995 and 2005, La Conchita, California: <\/b><span style=\"font-weight: 400\">On March 4, 1995, a fast-moving [pb_glossary id=\"3124\"]earthflow[\/pb_glossary] damaged nine houses in the southern California coastal community of La Conchita. A week later, a [pb_glossary id=\"3123\"]debris flow[\/pb_glossary] in the same location damaged five more houses. Surface-[pb_glossary id=\"1445\"]tension[\/pb_glossary] cracks at the top of the slide gave early warning signs in the summer of 1994. During the rainy winter season of 1994\/1995, the cracks grew larger. The likely [pb_glossary id=\"3117\"]trigger[\/pb_glossary] of the 1995 event was unusually heavy rainfall during the winter of 1994\/1995 and rising [pb_glossary id=\"3129\"]groundwater[\/pb_glossary] levels. Ten years later, in 2005, a rapid-[pb_glossary id=\"3123\"]debris flow[\/pb_glossary] occurred at the end of a 15-day [pb_glossary id=\"2192\"]period[\/pb_glossary] of near-record rainfall in southern California. Vegetation remained relatively intact as it was rafted on the surface of the rapid flow, indicating that much of the [pb_glossary id=\"1199\"]landslide[\/pb_glossary] mass simply was being carried on a presumably much more [pb_glossary id=\"2706\"]saturated[\/pb_glossary] and fluidized layer beneath. The 2005 slide damaged 36 houses and killed 10 people.<\/span>\n\n[caption id=\"attachment_3401\" align=\"aligncenter\" width=\"300\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.4_La_Conchita_oblique-LIDAR.jpg\"><img class=\"wp-image-683 size-medium\" title=\"Source: Todd Stennett, Airborne 1 Corp., El Segundo. Public domain\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_oblique-LIDAR-300x155.jpg\" alt=\"Image shows many slides in the area instead of just the one.\" width=\"300\" height=\"155\"><\/a> Oblique LIDAR image of La Conchita after the 2005 landslide. Outline of 1995 (blue) and 2005 (yellow) landslides shown; arrows show examples of other landslides in the area; red line outlines main scarp of an ancient landslide for the entire bluff. Source: Todd Stennett, Airborne 1 Corp., El Segundo. Public domain[\/caption]\n\n[caption id=\"attachment_3402\" align=\"aligncenter\" width=\"201\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.4_La_Conchita_1995.jpg\"><img class=\"wp-image-684 size-medium\" title=\"Source: USGS, Public Domain\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_1995-201x300.jpg\" alt=\"Image shows distinct scarp and slide material covering several houses.\" width=\"201\" height=\"300\"><\/a> 1995 La Conchita slide. Source: USGS[\/caption]\n\n[caption id=\"attachment_3403\" align=\"aligncenter\" width=\"400\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/USGS_MR_Oso_Aerial_clipped_adjusted.jpg\"><img class=\"wp-image-685\" title=\"Source: USGS, Public Domain\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/USGS_MR_Oso_Aerial_clipped_adjusted.jpg\" alt=\"Photo of large slide debris, flood from dammed river, distinct head scarp.\" width=\"400\" height=\"261\"><\/a> 2014 Oso slide in Washington killed 43 people and buried many homes (source: USGS, public domain).[\/caption]\n\n<b>2014, Oso [pb_glossary id=\"1199\"]Landslide[\/pb_glossary], Washington:<\/b> On March 22, 2014, a [pb_glossary id=\"1199\"]landslide[\/pb_glossary] of approximately 18 million tons (10 million yd<sup>3<\/sup>) traveled at 64 kph (40 mph), extended for nearly a 1.6 km (1 m), and dammed the North Fork of the Stillaguamish [pb_glossary id=\"3134\"]River[\/pb_glossary]. The [pb_glossary id=\"1199\"]landslide[\/pb_glossary] covered 40 homes and killed 43 people in the Steelhead Haven community near Oso, Washington. It produced a volume of material equivalent to 600 football fields covered in material 3 m (10 ft) deep. The winter of 2013-2014 was unusually wet with almost double the average amount of [pb_glossary id=\"2707\"]precipitation[\/pb_glossary]. The [pb_glossary id=\"1199\"]landslide[\/pb_glossary] occurred in an area of the Stillaguamish [pb_glossary id=\"3134\"]River[\/pb_glossary] Valley historically active with many [pb_glossary id=\"1199\"]landslides[\/pb_glossary], but previous events had been small.\n\n[caption id=\"attachment_3404\" align=\"aligncenter\" width=\"1024\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/JdLC-G_Oso-Landslide-Area-2014-Lidar-Map-scaled.jpg\"><img class=\"size-large wp-image-3404\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/JdLC-G_Oso-Landslide-Area-2014-Lidar-Map-scaled-1.jpg\" alt=\"Shaded releif map showing size of slide, flow direction arrows, home covered, and distinct scarp.\" width=\"1024\" height=\"663\"><\/a> Annotated Lidar map of 2014 Oso slide in Washington.[\/caption]\n\n<b>Yosemite National Park Rock [pb_glossary id=\"3119\"]Falls[\/pb_glossary]:<\/b><span style=\"font-weight: 400\"> The steep cliffs of Yosemite National Park cause frequent rock [pb_glossary id=\"3119\"]falls[\/pb_glossary]. [pb_glossary id=\"1934\"]Fractures[\/pb_glossary] created to [pb_glossary id=\"2576\"]tectonic[\/pb_glossary] [pb_glossary id=\"2915\"]stresses[\/pb_glossary] and [pb_glossary id=\"1205\"]exfoliation[\/pb_glossary] and expanded by [pb_glossary id=\"1207\"]frost wedging[\/pb_glossary] can cause house-sized blocks of [pb_glossary id=\"1962\"]granite[\/pb_glossary] to detach from the cliff-faces of Yosemite National Park.\u00a0 The park models potential runout, the distance [pb_glossary id=\"1199\"]landslide[\/pb_glossary] material travels, to better assess the risk posed to the millions of park visitors.\n<\/span>\n\n[caption id=\"attachment_4406\" align=\"alignleft\" width=\"150\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/Yosemite-Nature-Notes-Youtube-QR-Code.png\"><img class=\"size-thumbnail wp-image-687\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/Yosemite-Nature-Notes-Youtube-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\"><\/a> If you are using the printed version of this OER, access this YouTube video via this QR Code.[\/caption]\n\n[embed]https:\/\/www.youtube.com\/embed\/H0YhlqP1BgE[\/embed]\n\n<figcaption><span style=\"color: #333333\"><em><span style=\"font-size: 10pt\">[pb_glossary id=\"3119\"]<em>Rockfalls<\/em>[\/pb_glossary] in Yosemite.<\/span><\/em><\/span><\/figcaption><\/figure>\n<h4><span style=\"font-weight: 400\">Utah Landslides<\/span><\/h4>\n[caption id=\"attachment_3406\" align=\"aligncenter\" width=\"1024\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/snt45-2_markagunt-megabreccia-map-1030x741-1.gif\"><img class=\"size-large wp-image-688\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/snt45-2_markagunt-megabreccia-map-1030x741-1-1024x737.gif\" alt=\"Approximate extent of Markagunt Gravity slide.\" width=\"1024\" height=\"737\"><\/a> Approximate extent of Markagunt Gravity slide.[\/caption]\n\n<strong>Markagunt Gravity Slide: <\/strong>About 21\u201322 million years ago, one of the biggest land-based [pb_glossary id=\"1199\"]landslides[\/pb_glossary] yet discovered in the geologic record displaced more than 1,700 cu km (408 cu mi) of material in one relatively fast event. Evidence for this slide includes breccia [pb_glossary id=\"2833\"]conglomerates[\/pb_glossary] (<a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/5-weathering-erosion-and-sedimentary-rocks\/\">see Chapter 5<\/a>), glassy pseudotachylytes, (<a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/6-metamorphic-rocks\/\">see Chapter 6<\/a>), slip surfaces (similar to [pb_glossary id=\"3065\"]faults[\/pb_glossary]) <a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/9-crustal-deformation-and-earthquakes\/\">see Chapter 9<\/a>), and [pb_glossary id=\"1969\"]dikes[\/pb_glossary] (<a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/7-geologic-time\/\">see Chapter 7<\/a>). The [pb_glossary id=\"1199\"]landslide[\/pb_glossary] is estimated to encompass an area the size of Rhode Island and to extend from near Cedar City, Utah to Panguitch, Utah. This [pb_glossary id=\"1199\"]landslide[\/pb_glossary] was likely the result of material released from the side of a growing [pb_glossary id=\"1172\"]laccolith[\/pb_glossary] (a type of [pb_glossary id=\"2675\"]igneous[\/pb_glossary] intrusion) <a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/4-igneous-processes-and-volcanoes\/\">see Chapter 4<\/a>), after being triggered by an eruption-related earthquake.\n\n&nbsp;\n\n[caption id=\"attachment_3390\" align=\"aligncenter\" width=\"534\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/Thistlelandslideusgs.jpg\"><img class=\"wp-image-669\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs.jpg\" alt=\"The 1983 Thistle landslide (foreground) dammed the Spanish Fork river creating a lake.\" width=\"534\" height=\"362\"><\/a> The 1983 Thistle landslide (foreground) dammed the Spanish Fork river creating a lake.[\/caption]\n\n<b>1983, Thistle Slide:<\/b><span style=\"font-weight: 400\">\u00a0<\/span><span style=\"font-weight: 400\">Starting in April of 1983 and continuing into May of that year, a slow-moving [pb_glossary id=\"1199\"]landslide[\/pb_glossary] traveled 305 m (1,000 ft) downhill and blocked Spanish Fork Canyon with an [pb_glossary id=\"3124\"]earthflow[\/pb_glossary] dam 61 m (200 ft) high. This caused disastrous flooding upstream in the Soldier Creek and Thistle Creek valleys, submerging the town of Thistle. As part of the emergency response, a spillway was constructed to prevent the newly formed lake from breaching the dam. Later, a tunnel was constructed to drain the lake, and currently the [pb_glossary id=\"3134\"]river[\/pb_glossary] continues to flow through this tunnel. The rail line and US-6 highway had to be relocated at a cost of more than $200 million.<\/span>\n\n[caption id=\"attachment_3407\" align=\"aligncenter\" width=\"1024\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.4_Rockville1-e1491186191527.png\"><img class=\"size-large wp-image-689\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville1-e1491186191527-1024x442.png\" alt=\"House before and after destruction from 2013 Rockville rockfall.\" width=\"1024\" height=\"442\"><\/a> House before and after destruction from 2013 Rockville rockfall.[\/caption]\n\n<b>2013, Rockville [pb_glossary id=\"3119\"]Rock Fall[\/pb_glossary]:<\/b>Rockville, Utah is a small community near the entrance to Zion National Park. In December of 2013, a 2,700 ton (1,400 yd<sup>3<\/sup>) block of Shinarump [pb_glossary id=\"2833\"]Conglomerate[\/pb_glossary] fell from the Rockville Bench cliff, landed on the steep 35-degree slope below, and shattered into several large pieces that continued downslope at a high speed. These boulders completely destroyed a house located 375 feet below the cliff (see the before and after photographs) and killed two people inside the home. The topographic map shows other rock [pb_glossary id=\"3119\"]falls[\/pb_glossary] in the area prior to this catastrophic event.\n\n[caption id=\"attachment_3409\" align=\"aligncenter\" width=\"487\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.4_Rockville2.png\"><img class=\"wp-image-690\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville2-1024x926.png\" alt=\"Tracks of deadly 2013 Rockville rocksfall and earlier documented rockfall events.\" width=\"487\" height=\"440\"><\/a> Tracks of deadly 2013 Rockville rocksfall and earlier documented rockfall events.[\/caption]\n\n<b>2014, North Salt Lake Slide:<\/b><span style=\"font-weight: 400\"> In August 2014 after a particularly wet [pb_glossary id=\"2192\"]period[\/pb_glossary], a slow moving rotational [pb_glossary id=\"1199\"]landslide[\/pb_glossary] destroyed one home and damaged nearby tennis courts<\/span><span style=\"font-weight: 400\">.<\/span>\n\n[caption id=\"attachment_3410\" align=\"aligncenter\" width=\"461\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/RS9196__MG_6439-scaled.jpg\"><img class=\"wp-image-3410\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/RS9196__MG_6439-scaled-1.jpg\" alt=\"Scarp and displaced material from the North Salt Lake (Parkview) slide of 2014.\" width=\"461\" height=\"323\"><\/a> Scarp and displaced material from the North Salt Lake (Parkview) slide of 2014.[\/caption]\n\n<span style=\"font-weight: 400\">Reports from residents suggested that ground cracks had been seen near the top of the slope at least a year prior to the catastrophic movement. <\/span><span style=\"font-weight: 400\">The presence of easily-drained sands and gravels overlying more impermeable clays weathered from [pb_glossary id=\"1181\"]volcanic[\/pb_glossary] [pb_glossary id=\"1949\"]ash[\/pb_glossary], along with recent regrading of the slope, \u00a0may have been contributing causes of this slide. \u00a0Local heavy rains seem to have provided the [pb_glossary id=\"3117\"]trigger[\/pb_glossary]. \u00a0In the two years after the [pb_glossary id=\"1199\"]landslide[\/pb_glossary], the slope has been partially regraded to increase its stability. Unfortunately, in January 2017, parts of the slope have shown reactivation movement. Similarly, in 1996 residents in a nearby subdivision started reporting distress to their homes. \u00a0This distress continued until 2012 when 18 homes became uninhabitable due to extensive \u00a0damage and were removed. A geologic park was constructed in the now vacant area.<\/span>\n\n[caption id=\"attachment_4405\" align=\"alignleft\" width=\"150\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/Time-lapse-video-of-landslide-Youtube-QR-Code.png\"><img class=\"size-thumbnail wp-image-692\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/Time-lapse-video-of-landslide-Youtube-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\"><\/a> If you are using the printed version of this OER, access this YouTube video via this QR Code.[\/caption]\n\n[embed]https:\/\/www.youtube.com\/embed\/NQs_OWgNshg[\/embed]\n\n<span style=\"color: #333333\"><em><span style=\"font-size: 10pt\">North Salt Lake Landslide<\/span><\/em><\/span>\n\n<strong>2013, Bingham Canyon Copper [pb_glossary id=\"3324\"]Mine[\/pb_glossary] [pb_glossary id=\"1199\"]Landslide[\/pb_glossary], Utah:<\/strong> At 9:30 pm on April 10, 2013, more than 65 million cubic meters of steep terraced [pb_glossary id=\"3324\"]mine[\/pb_glossary] wall slid down into the engineered pit of Bingham Canyon [pb_glossary id=\"3324\"]mine[\/pb_glossary], making it one of the largest historic [pb_glossary id=\"1199\"]landslides[\/pb_glossary] not associated with [pb_glossary id=\"1181\"]volcanoes[\/pb_glossary].\u00a0 Radar systems maintained by the [pb_glossary id=\"3324\"]mine[\/pb_glossary] operator warned of movement of the wall, preventing the loss of life and limiting the loss of property.\n\n&nbsp;\n\n[h5p id=\"71\"]\n\n[caption id=\"attachment_4411\" align=\"aligncenter\" width=\"150\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code.png\"><img class=\"size-thumbnail wp-image-693\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\"><\/a> If you are using the printed version of this OER, access this interactive activity via this QR Code.[\/caption]\n\n&nbsp;\n<h3>Take this quiz to check your comprehension of this section.<\/h3>\n[h5p id=\"72\"]\n\n[caption id=\"attachment_4402\" align=\"aligncenter\" width=\"150\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10.4-Did-I-Get-It-QR-Code.png\"><img class=\"size-thumbnail wp-image-694\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Did-I-Get-It-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\"><\/a> If you are using the printed version of this OER, access the quiz for section 10.4 via this QR Code.[\/caption]\n<h2><strong>10.5 Chapter Summary<\/strong><\/h2>\n[pb_glossary id=\"3110\"]Mass wasting[\/pb_glossary] is a geologic term describing all downhill rock and [pb_glossary id=\"1203\"]soil[\/pb_glossary] movement due to gravity. [pb_glossary id=\"3110\"]Mass wasting[\/pb_glossary] occurs when a slope is too steep to remain stable with existing material and conditions. Loose rock and [pb_glossary id=\"1203\"]soil[\/pb_glossary], called [pb_glossary id=\"3111\"]regolith[\/pb_glossary], are what typically move during a mass-wasting event. Slope stability is determined by two factors: the angle of the slope and the [pb_glossary id=\"3114\"]shear strength[\/pb_glossary] of the accumulated materials. Mass-wasting events are triggered by changes that [pb_glossary id=\"3118\"]oversteepen[\/pb_glossary] slope angles and weaken slope stability, such as rapid snow melt, intense rainfall, earthquake shaking, [pb_glossary id=\"1181\"]volcanic[\/pb_glossary] eruption, storm waves, [pb_glossary id=\"3134\"]stream[\/pb_glossary] [pb_glossary id=\"2677\"]erosion[\/pb_glossary], and human activities. Excessive [pb_glossary id=\"2707\"]precipitation[\/pb_glossary] is the most common trigger. Mass-wasting events are classified by their type of movement and material, and they share common morphological surface features. The most common types of mass-wasting events are [pb_glossary id=\"3119\"]rockfalls[\/pb_glossary], slides, flows, and [pb_glossary id=\"2447\"]creep[\/pb_glossary].\n\nMass-wasting movement ranges from slow to dangerously rapid. Areas with steep topography and rapid rainfall, such as the California [pb_glossary id=\"2890\"]coast[\/pb_glossary], Rocky Mountain Region, and Pacific Northwest, are particularly susceptible to hazardous mass-wasting events. By examining examples and lessons learned from famous mass-wasting events, scientists have a better understanding of how mass-wasting occurs. This knowledge has brought them closer to predicting where and how these potentially hazardous events may occur and how people can be protected.\n<h3>Take this quiz to check your comprehension of this Chapter.<\/h3>\n[h5p id=\"73\"]\n\n[caption id=\"attachment_4403\" align=\"aligncenter\" width=\"150\"]<a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/Ch.10-Review-QR-Code.png\"><img class=\"size-thumbnail wp-image-695\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/Ch.10-Review-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\"><\/a> If you are using the printed version of this OER, access the review quiz for Chapter 10 via this QR Code.[\/caption]\n<h2><span style=\"font-weight: 400\">References<\/span><\/h2>\n<div class=\"csl-bib-body\">\n<ol>\n \t<li class=\"csl-entry\">Haugerud, R.A., 2014, Preliminary interpretation of pre-2014 [pb_glossary id=\"1199\"]landslide[\/pb_glossary] deposits in the vicinity of Oso, Washington: US Geological Survey.<\/li>\n \t<li class=\"csl-entry\">Highland, L., 2004, [pb_glossary id=\"1199\"]Landslide[\/pb_glossary] types and processes: pubs.er.usgs.gov.<\/li>\n \t<li class=\"csl-entry\">Highland, L.M., and Bobrowsky, P., 2008, The [pb_glossary id=\"1199\"]Landslide[\/pb_glossary] Handbook - A Guide to Understanding [pb_glossary id=\"1199\"]Landslides[\/pb_glossary]: U.S. Geological Survey USGS Numbered Series 1325, 147 p.<\/li>\n \t<li class=\"csl-entry\">Highland, L.M., and Schuster, R.L., 2000, Significant [pb_glossary id=\"1199\"]landslide[\/pb_glossary] events in the United States: United States Geological Survey.<\/li>\n \t<li class=\"csl-entry\">Hildenbrand, T.G., and Hendricks, J.D., 1995, Geophysical setting of the Reelfoot [pb_glossary id=\"2624\"]rift[\/pb_glossary] and relations between [pb_glossary id=\"2624\"]rift[\/pb_glossary] structures and the New Madrid [pb_glossary id=\"3087\"]seismic[\/pb_glossary] zone: U.S. Geological Survey Professional Paper 1538-E, 36 p.<\/li>\n \t<li class=\"csl-entry\">Hungr, O., Leroueil, S., and Picarelli, L., 2013, The Varnes classification of [pb_glossary id=\"1199\"]landslide[\/pb_glossary] types, an update: [pb_glossary id=\"1199\"]Landslides[\/pb_glossary], v. 11, no. 2, p. 167\u2013194.<\/li>\n \t<li class=\"csl-entry\">Jibson, R.W., 2005, [pb_glossary id=\"1199\"]Landslide[\/pb_glossary] hazards at La Conchita, California: United States Geological Survey Open-File Report 2005-1067.<\/li>\n \t<li class=\"csl-entry\">Lipman, P.W., and Mullineaux, D.R., 1981, The 1980 eruptions of Mount St. Helens, Washington: US Geological Survey USGS Numbered Series 1250, 844 p., doi: <a href=\"https:\/\/doi.org\/10.3133\/pp1250\">10.3133\/pp1250<\/a>.<\/li>\n \t<li class=\"csl-entry\">Lund, W.R., Knudsen, T.R., and Bowman, S.D., 2014, Investigation of the December 12, 2013, Fatal [pb_glossary id=\"3119\"]Rock Fall[\/pb_glossary] at 368 West Main Street, Rockville, Utah: Utah Geological Survey 273, 24 p.<\/li>\n \t<li class=\"csl-entry\">United States Forest Service, 2016, A Brief History of the Gros Ventre Slide Geological Site: United States Forest Service.<\/li>\n<\/ol>\n<\/div>","rendered":"<figure id=\"attachment_3390\" aria-describedby=\"caption-attachment-3390\" style=\"width: 800px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/Thistlelandslideusgs.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-669\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs.jpg\" alt=\"The 1983 Thistle landslide (foreground) dammed the Spanish Fork river creating a lake.\" width=\"800\" height=\"543\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs.jpg 800w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs-300x204.jpg 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs-768x521.jpg 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs-65x44.jpg 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs-225x153.jpg 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs-350x238.jpg 350w\" sizes=\"auto, (max-width: 800px) 100vw, 800px\" \/><\/a><figcaption id=\"caption-attachment-3390\" class=\"wp-caption-text\">The 1983 Thistle landslide (foreground) dammed the Spanish Fork River creating a lake that covered the town of Thistle, Utah. The slide covered Hwy 6 and the main railroad between Salt Lake and Denver.<\/figcaption><\/figure>\n<h1>10 Mass Wasting<\/h1>\n<p><b>KEY CONCEPTS<\/b><\/p>\n<p><b>At the end of this chapter, students should be able to:<\/b><\/p>\n<ul>\n<li>Explain what <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">mass wasting<\/a> is and why it occurs on a slope<\/li>\n<li>Explain the basic triggers of mass-wasting events and how they occur<\/li>\n<li>Identify types of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">mass wasting<\/a><\/li>\n<li>Identify risk factors for mass-wasting events<\/li>\n<li>Evaluate <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> and their contributing factors<\/li>\n<\/ul>\n<p>This chapter discusses the fundamental processes driving mass-wasting, types of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">mass wasting<\/a>, examples and lessons learned from famous mass-wasting events, how <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">mass wasting<\/a> can be predicted, and how people can be protected from this potential hazard. <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">Mass wasting<\/a><\/strong> is the downhill movement of rock and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soil<\/a> material due to gravity. The term <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> is often used as a synonym for <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">mass wasting<\/a>, but <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">mass wasting<\/a> is a much broader term referring to all movement downslope. Geologically, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> is a general term for <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">mass wasting<\/a> that involves fast-moving geologic material. Loose material along with overlying <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soils<\/a> are what typically move during a mass-wasting event. Moving blocks of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1971\">bedrock<\/a> are called rock topples, rock slides, or rock <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">falls<\/a>, depending on the dominant motion of the blocks. Movements of dominantly liquid material are called flows. Movement by <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">mass wasting<\/a> can be slow or rapid. Rapid movement can be dangerous, such as during <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3123\">debris flows<\/a>. Areas with steep topography and rapid rainfall, such as the California <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2890\">coast<\/a>, Rocky Mountain Region, and Pacific Northwest, are particularly susceptible to hazardous mass-wasting events.<\/p>\n<h2><span style=\"font-weight: 400\">10.1 Slope Strength<\/span><\/h2>\n<figure id=\"attachment_3391\" aria-describedby=\"caption-attachment-3391\" style=\"width: 359px\" class=\"wp-caption alignright\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.1_Block_on_Incline.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-670\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Block_on_Incline.png\" alt=\"Forces on a block on an inclined plane (fg = force of gravity; fn = normal force; fs = shear force).\" width=\"359\" height=\"188\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Block_on_Incline.png 974w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Block_on_Incline-300x157.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Block_on_Incline-768x401.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Block_on_Incline-65x34.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Block_on_Incline-225x118.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Block_on_Incline-350x183.png 350w\" sizes=\"auto, (max-width: 359px) 100vw, 359px\" \/><\/a><figcaption id=\"caption-attachment-3391\" class=\"wp-caption-text\">Forces on a block on an inclined plane (fg = force of gravity; fn = normal force; fs = shear force).<\/figcaption><\/figure>\n<p><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">Mass wasting<\/a> occurs when a slope fails. A slope fails when it is too steep and unstable for existing materials and conditions. Slope stability is ultimately determined by two principal factors: the slope angle and the strength of the underlying material. Force of gravity, which plays a part in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">mass wasting<\/a>, is constant on the Earth\u2019s surface for the most part, although small variations exist depending on the elevation and density of the underlying rock. In the figure, a block of rock situated on a slope is pulled down toward the Earth\u2019s center by the force of gravity (fg). The gravitational force acting on a slope can be divided into two components: the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1447\">shear<\/a> or <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3112\">driving force<\/a> (fs) pushing the block down the slope, and the normal or <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3113\">resisting force<\/a> (fn) pushing into the slope, which produces friction. The relationship between <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3112\">shear force<\/a> and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3113\">normal force<\/a> is called <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3114\">shear strength<\/a>. When the normal force, i.e., friction, is greater than the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3112\">shear force<\/a>, then the block does <em>not <\/em>move downslope. However, if the slope angle becomes steeper or if the earth material is weakened, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3112\">shear force<\/a> exceeds <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3113\">normal force<\/a>, compromising <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3114\">shear strength<\/a>, and downslope movement occurs.<\/p>\n<figure id=\"attachment_3392\" aria-describedby=\"caption-attachment-3392\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.1_blocks-on-incline.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-671\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_blocks-on-incline-1024x291.png\" alt=\"As slope increases, the force of gravity (fg) stays the same and the normal force decreases while the shear force proportionately increases.\" width=\"1024\" height=\"291\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_blocks-on-incline-1024x291.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_blocks-on-incline-300x85.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_blocks-on-incline-768x219.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_blocks-on-incline-1536x437.png 1536w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_blocks-on-incline-2048x583.png 2048w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_blocks-on-incline-65x18.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_blocks-on-incline-225x64.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_blocks-on-incline-350x100.png 350w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><figcaption id=\"caption-attachment-3392\" class=\"wp-caption-text\">As slope increases, the force of gravity (fg) stays the same and the normal force decreases while the shear force proportionately increases.<\/figcaption><\/figure>\n<p>In the figure, the force vectors change as the slope angle increases. The gravitational force doesn\u2019t change, but the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3112\">shear force<\/a> increases while the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3113\">normal force<\/a> decreases. The steepest angle at which rock and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soil<\/a> material is stable and will <em>not<\/em> move downslope is called the <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3115\">angle of repose<\/a>.<\/strong> The <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3115\">angle of repose<\/a> is measured relative from the horizontal. When a slope is at the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3115\">angle of repose<\/a>, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3112\">shear force<\/a> is in equilibrium with the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3113\">normal force<\/a>. If the slope becomes just slightly steeper, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3112\">shear force<\/a> exceeds the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3113\">normal force<\/a>, and the material starts to move downhill. The <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3115\">angle of repose<\/a> varies for all material and slopes depending on many factors such as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2828\">grain size<\/a>, grain <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2831\">composition<\/a>, and water content. The figure shows the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3115\">angle of repose<\/a> for sand that is poured into a pile on a flat surface. The sand grains cascade down the sides of the pile until coming to rest at the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3115\">angle of repose<\/a>. At that angle, the base and height of the pile continue to increase, but the angle of the sides remains the same.<span style=\"font-weight: 400\">\u00a0<\/span><\/p>\n<figure id=\"attachment_3393\" aria-describedby=\"caption-attachment-3393\" style=\"width: 300px\" class=\"wp-caption alignleft\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.1_Angleofrepose.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-672 size-medium\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Angleofrepose-300x167.png\" alt=\"Angle of repose in a pile of sand.\" width=\"300\" height=\"167\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Angleofrepose-300x167.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Angleofrepose-65x36.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Angleofrepose-225x126.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Angleofrepose-350x195.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1_Angleofrepose.png 430w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-3393\" class=\"wp-caption-text\">Angle of repose in a pile of sand.<\/figcaption><\/figure>\n<p>Water is a common factor that can significantly change the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3114\">shear strength<\/a> of a particular slope. Water is located in <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3116\">pore<\/a> spaces<\/strong>, which are empty air spaces in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2678\">sediments<\/a> or rocks between the grains. For example, assume a dry sand pile has an <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3115\">angle of repose<\/a> of 30 degrees. If water is added to the sand, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3115\">angle of repose<\/a> will increase, possibly to 60 degrees or even 90 degrees, such as a sandcastle being built at a beach. But if too much water is added to the pore spaces of the sandcastle, the water decreases the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3114\">shear strength<\/a>, lowers the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3115\">angle of repose<\/a>, and the sandcastle collapses.<\/p>\n<p>Another factor influencing <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3114\">shear strength<\/a> are planes of weakness in sedimentary rocks. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2857\">Bedding<\/a> planes (<a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/5-weathering-erosion-and-sedimentary-rocks\/\">see Chapter 5<\/a>) can act as significant planes of weakness when they are parallel to the slope but less so if they are perpendicular to the slope. At locations A and B, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2857\">bedding<\/a> is nearly perpendicular to the slope and relatively stable. At location D, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2857\">bedding<\/a> is nearly parallel to the slope and quite unstable. At location C, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2857\">bedding<\/a> is nearly horizontal, and the stability is <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1955\">intermediate<\/a> between the other two extremes [1]. Additionally, if clay <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3375\">minerals<\/a> form along <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2857\">bedding<\/a> planes, they can absorb water and become slick. When a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2857\">bedding<\/a> plane of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2839\">shale<\/a> (clay and silt) becomes <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2706\">saturated<\/a>, it can lower the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3114\">shear strength<\/a> of the rock mass and cause a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a>, such as at the 1925 Gros Ventre, Wyoming rock slide. See the case studies section for details on this and other <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a>.<\/p>\n<figure id=\"attachment_3394\" aria-describedby=\"caption-attachment-3394\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-673\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses-1024x356.png\" alt=\"At locations A and B, the bedding is nearly perpendicular to the slope and the bedding is relatively stable. At location D, the bedding is nearly parallel to the slope and the bedding is quite unstable. At location C the bedding is nearly horizontal and the stability is intermediate between the other two extremes.\" width=\"1024\" height=\"356\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses-1024x356.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses-300x104.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses-768x267.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses-65x23.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses-225x78.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses-350x122.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Relative-stability-of-slopes-as-a-function-of-the-orientation-of-weaknesses.png 1191w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><figcaption id=\"caption-attachment-3394\" class=\"wp-caption-text\">Locations A and B have bedding nearly perpendicular to the slope, making for a relatively stable slope. Location D has bedding nearly parallel to the slope, increasing the risk of slope failure. Location C has bedding nearly horizontal and the stability is relatively intermediate.<\/figcaption><\/figure>\n<h3>Take this quiz to check your comprehension of this section.<\/h3>\n<div id=\"h5p-67\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-67\" class=\"h5p-iframe\" data-content-id=\"67\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"10.1 Did I Get It?\"><\/iframe><\/div>\n<\/div>\n<figure id=\"attachment_4398\" aria-describedby=\"caption-attachment-4398\" style=\"width: 150px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10.1-Did-I-Get-It-QR-Code.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-674 size-thumbnail\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1-Did-I-Get-It-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1-Did-I-Get-It-QR-Code-150x150.png 150w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1-Did-I-Get-It-QR-Code-300x300.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1-Did-I-Get-It-QR-Code-1024x1024.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1-Did-I-Get-It-QR-Code-768x768.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1-Did-I-Get-It-QR-Code-65x65.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1-Did-I-Get-It-QR-Code-225x225.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1-Did-I-Get-It-QR-Code-350x350.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.1-Did-I-Get-It-QR-Code.png 1147w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a><figcaption id=\"caption-attachment-4398\" class=\"wp-caption-text\">If you are using the printed version of this OER, access the quiz for section 10.1 via this QR Code.<\/figcaption><\/figure>\n<h2><span style=\"font-weight: 400\">10.2 Mass-Wasting Triggers &amp; Mitigation<br \/>\n<\/span><\/h2>\n<p>Mass-wasting events often have a <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3117\">trigger<\/a><\/strong>: something changes that causes a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> to occur at a specific time. It could be rapid snowmelt, intense rainfall, earthquake shaking, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1181\">volcanic<\/a> eruption, storm waves, rapid-<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">stream<\/a> <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2677\">erosion<\/a>, or human activities, such as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2862\">grading<\/a> a new road. Increased water content within the slope is the most common mass-wasting <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3117\">trigger<\/a>. Water content can increase due to rapidly melting snow or ice or an intense rain event. Intense rain events can occur more often during El Ni\u00f1o years. Then, the west <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2890\">coast<\/a> of North America receives more <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2707\">precipitation<\/a> than normal, and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> become more common. Changes in surface-water conditions resulting from earthquakes, previous slope failures that dam up <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">streams<\/a>, or human structures that interfere with <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3127\">runoff<\/a>, such as \u00a0buildings, roads, or parking lots can provide additional water to a slope. In the case of the 1959 Hebgen Lake rock slide, Madison Canyon, Montana, the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3114\">shear strength<\/a> of the slope may have been weakened by earthquake shaking. Most <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> mitigation diverts and drains water away from slide areas.\u00a0 Tarps and plastic sheeting\u00a0 are often used to drain water off of slide bodies and prevent <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3128\">infiltration<\/a> into the slide. Drains are used to dewater <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> and shallow wells are used to monitor the water content of some active <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a>.<\/p>\n<p>An <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3118\">oversteepened<\/a><\/strong> slope may also <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3117\">trigger<\/a> <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a>. Slopes can be made excessively steep by natural processes of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2677\">erosion<\/a> or when humans modify the landscape for building construction. An example of how a slope may be <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3118\">oversteepened<\/a> during development occurs where the bottom of the slope is cut into, perhaps to build a road or level a building lot, and the top of the slope is modified by depositing excavated material from below. If done carefully, this practice can be very useful in land development, but in some cases, this can result in devastating consequences. For example, this might have been a contributing factor in the 2014 North Salt Lake City, Utah <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a>. A former gravel pit was regraded to provide a road and several building lots. These activities may have <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3118\">oversteepened<\/a> the slope, which resulted in a slow moving <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> that destroyed one home at the bottom of the slope. Natural processes such as excessive <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">stream<\/a> <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2677\">erosion<\/a> from a flood or coastal erosion during a storm can also <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3118\">oversteepen<\/a> slopes. For example, natural undercutting of the riverbank was proposed as part of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3117\">trigger<\/a> for the famous 1925 Gros Ventre, Wyoming rock slide.<\/p>\n<p>Slope reinforcement can help prevent and mitigate <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> .\u00a0 For <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">rockfall<\/a>-prone areas, sometimes it is economical to use long steel bolts. Bolts, drilled a few meters into a rock face, can secure loose pieces of material that could pose a hazard. Shockcrete, a reinforced spray-on form of concrete, can strengthen a slope face when applied properly. Buttressing a slide by adding weight at the toe of the slide and removing weight from the head of the slide, can stabilize a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a>.\u00a0 Terracing, which creates a stairstep topography, can be applied to help with slope stabilization, but it must be applied at the proper scale to be effective.<\/p>\n<p>A different approach in reducing <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> hazard is to <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2207\">shield<\/a>, catch, and divert the runout material.\u00a0 Sometimes the most economical way to deal with a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> hazard is to divert and slow the falling material.\u00a0 Special stretchable fencing can be applied in areas where <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">rockfall<\/a> is common to protect pedestrians and vehicles.\u00a0 Runout channels, diversion structures, and check dams can be used to slow <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3123\">debris flows<\/a> and divert them around structures.\u00a0 Some highways have special tunnels that divert <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> over the highway.\u00a0 In all of these cases the shielding has to be engineered to a scale that is greater than the slide, or catastrophic loss in property and life could result.<\/p>\n<h3>Take this quiz to check your comprehension of this section.<\/h3>\n<div id=\"h5p-68\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-68\" class=\"h5p-iframe\" data-content-id=\"68\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"10.2 Did I Get It?\"><\/iframe><\/div>\n<\/div>\n<figure id=\"attachment_4399\" aria-describedby=\"caption-attachment-4399\" style=\"width: 150px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10.2-Did-I-Get-It-QR-Code.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-thumbnail wp-image-675\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.2-Did-I-Get-It-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.2-Did-I-Get-It-QR-Code-150x150.png 150w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.2-Did-I-Get-It-QR-Code-300x300.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.2-Did-I-Get-It-QR-Code-1024x1024.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.2-Did-I-Get-It-QR-Code-768x768.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.2-Did-I-Get-It-QR-Code-65x65.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.2-Did-I-Get-It-QR-Code-225x225.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.2-Did-I-Get-It-QR-Code-350x350.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.2-Did-I-Get-It-QR-Code.png 1147w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a><figcaption id=\"caption-attachment-4399\" class=\"wp-caption-text\">If you are using the printed version of this OER, access the quiz for section 10.2 via this QR Code.<\/figcaption><\/figure>\n<h2><span style=\"font-weight: 400\">10.3 Landslide Classification &amp; Identification<br \/>\n<\/span><\/h2>\n<p>Mass-wasting events are classified by type of movement and type of material, and there are several ways to classify these events. The figure and table show terms used. In addition, mass-wasting types often share common morphological features observed on the surface, such as the head scarp\u2014commonly seen as crescent shapes on a cliff face; hummocky or uneven surfaces; accumulations of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3370\">talus<\/a>\u2014loose rocky material falling from above; and toe of slope, which covers existing surface material. <code><\/code><\/p>\n<h3><strong>10.3.1 Types of Mass Wasting<\/strong><\/h3>\n<p>The most common mass-wasting types are <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">falls<\/a>, rotational and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3121\">translational slides<\/a>, flows, and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2447\">creep<\/a>. <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">Falls<\/a><\/strong> are abrupt rock movements that detach from steep slopes or cliffs. Rocks separate along existing natural breaks such as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1934\">fractures<\/a> or <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2857\">bedding<\/a> planes. Movement occurs as free-falling, bouncing, and rolling. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">Falls<\/a> are strongly influenced by gravity, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1204\">mechanical weathering<\/a>, and water. <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3120\">Rotational slides<\/a><\/strong> commonly show slow movement along a curved rupture surface. <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3121\">Translational slides<\/a><\/strong> often are rapid movements along a plane of distinct weakness between the overlying slide material and more stable underlying material. Slides can be further subdivided into rock slides, debris slides, or earth slides depending on the type of the material involved (see table).<\/p>\n<table class=\"aligncenter\" style=\"width: 100%;border-style: none;border-color: #000000\">\n<caption><span style=\"font-size: 10pt\"><em>Table of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\"><em>Mass Wasting<\/em><\/a> Types. \u00a0<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\"><em>Mass wasting<\/em><\/a> movement type and primary earth material. Modified from [zotpressInText item=&#8221;{948446:KG8X6AAJ},{948446:HN9CI37K}&#8221; format=&#8221;(%num%)&#8221; brackets=&#8221;yes&#8221;].<\/em><\/span><\/caption>\n<tbody>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\" rowspan=\"3\">&nbsp;<\/p>\n<p><b>Type of Movement<\/b><\/td>\n<td style=\"width: 76.4277%;background-color: #68e88a;border-color: #000000;text-align: center\" colspan=\"3\"><b>Primary Material Type and Common Name of Slide<\/b><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 26.61%;background-color: #68e88a;border-color: #000000;text-align: center\" rowspan=\"2\"><b><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1971\">Bedrock<\/a><\/b><\/td>\n<td style=\"width: 49.8177%;background-color: #68e88a;border-color: #000000;text-align: center\" colspan=\"2\"><b><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">Soil<\/a> Types<\/b><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 24.9089%;background-color: #68e88a;border-color: #000000;text-align: center\"><b>Mostly Coarse-Grained<\/b><\/td>\n<td style=\"width: 24.9089%;background-color: #68e88a;border-color: #000000;text-align: center\"><b>Mostly Fine-Grained<\/b><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">Falls<\/a><\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\"><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">Rock Fall<\/a><\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">&#8212;<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">&#8212;<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b>Rock Avalanche<\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Rock Avalanche<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">&#8212;<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">&#8212;<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3120\">Rotational Slide<\/a> (Slump)<\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">&#8212;<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Rotational Debris Slide (Slump)<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Rotational Earth Slide (Slump)<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3121\">Translational Slide<\/a><\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Translational Rock Slide<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Translational Debris Slide<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">Translational Earth Slide<\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b>Flows<\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">&#8212;<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\"><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3123\">Debris Flow<\/a><\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\"><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3124\">Earth flow<\/a><\/span><\/td>\n<\/tr>\n<tr>\n<td style=\"width: 23.578%;background-color: #88f0f7;border-color: #000000;text-align: center\" colspan=\"2\"><b><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3125\">Soil Creep<\/a><\/b><\/td>\n<td style=\"width: 26.61%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\">&#8212;<\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\"><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2447\">Creep<\/a><\/span><\/td>\n<td style=\"width: 24.9089%;background-color: #fcfcfc;border-color: #000000;text-align: center\"><span style=\"font-weight: 400\"><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2447\">Creep<\/a><\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><em><span style=\"font-weight: 400\">\u00a0<\/span><\/em><\/p>\n<figure id=\"attachment_3395\" aria-describedby=\"caption-attachment-3395\" style=\"width: 548px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.3_Fig3grouping-2LG.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-676\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3_Fig3grouping-2LG.jpg\" alt=\"Examples of some of the types of landslides.\" width=\"548\" height=\"663\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3_Fig3grouping-2LG.jpg 548w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3_Fig3grouping-2LG-248x300.jpg 248w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3_Fig3grouping-2LG-65x79.jpg 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3_Fig3grouping-2LG-225x272.jpg 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3_Fig3grouping-2LG-350x423.jpg 350w\" sizes=\"auto, (max-width: 548px) 100vw, 548px\" \/><\/a><figcaption id=\"caption-attachment-3395\" class=\"wp-caption-text\">Examples of some of the types of landslides.<\/figcaption><\/figure>\n<p>Flows are rapidly moving mass-wasting events in which the loose material is typically mixed with abundant water, creating long runouts at the slope base. Flows are commonly separated into <b><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3123\">debris flow<\/a><\/b> (coarse material)\u00a0and <b><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3124\">earthflow<\/a><\/b> (fine material) depending on the type of material involved and the amount of water. Some of the largest and fastest flows on land are called <strong><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3122\">sturzstroms<\/a><\/strong>, or long runout <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a>. They are still poorly understood, but are known to travel for long distances, even in places without significant atmospheres like the Moon.<\/p>\n<p><b><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2447\">Creep<\/a><\/b> is the imperceptibly slow downward movement of material caused by a regular cycle of nighttime freezing followed by daytime thawing in unconsolidated material such as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soil<\/a>. During the freeze, expansion of ice pushes <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soil<\/a> particles out away from the slope, while the next day following the thaw, gravity pulls them directly downward. The net effect is a gradual movement of surface <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soil<\/a> particles downhill. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2447\">Creep<\/a> is indicated by curved tree trunks, bent fences or retaining walls, tilted poles or fences, and small <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soil<\/a> <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2868\">ripples<\/a> or ridges. A special type of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3125\">soil creep<\/a> is solifluction, which is the slow movement of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soil<\/a> lobes on low-angle slopes due to <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soil<\/a> seasonally freezing and thawing in high-<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3372\">latitude<\/a>, typically sub-Arctic, Arctic, and Antarctic locations.<\/p>\n<p>&nbsp;<\/p>\n<figure>\n<figure id=\"attachment_4404\" aria-describedby=\"caption-attachment-4404\" style=\"width: 150px\" class=\"wp-caption alignleft\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/Landslide-Hazards-Youtube-QR-Code.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-thumbnail wp-image-677\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/Landslide-Hazards-Youtube-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Landslide-Hazards-Youtube-QR-Code-150x150.png 150w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Landslide-Hazards-Youtube-QR-Code-300x300.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Landslide-Hazards-Youtube-QR-Code-1024x1024.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Landslide-Hazards-Youtube-QR-Code-768x768.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Landslide-Hazards-Youtube-QR-Code-65x65.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Landslide-Hazards-Youtube-QR-Code-225x225.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Landslide-Hazards-Youtube-QR-Code-350x350.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Landslide-Hazards-Youtube-QR-Code.png 1155w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a><figcaption id=\"caption-attachment-4404\" class=\"wp-caption-text\">If you are using the printed version of this OER, access this YouTube video via this QR Code.<\/figcaption><\/figure>\n<p><iframe loading=\"lazy\" id=\"oembed-1\" title=\"Landslide Hazards\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/MVwSpGVfWVo?feature=oembed&#38;rel=0&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p><span style=\"font-size: 10pt;color: #333333\"><em><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\"><em>Landslide<\/em><\/a> Hazards, David Applegate<\/em><\/span><\/p>\n<h3><strong>10.3.2 Parts of a Landslide<\/strong><\/h3>\n<p><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">Landslides<\/a> have several identifying features that can be common across the different types of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">mass wasting<\/a>. Note that there are many exceptions, and a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> does not have to have these features. Displacement of material by <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> causes the absence of material uphill and the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2679\">deposition<\/a> of new material downhill, and careful <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2651\">observation<\/a> can identify the evidence of that displacement. Other signs of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> include tilted or <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3081\">offset<\/a> structures or natural features that would normally be vertical or in place.<br \/>\nMany <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> have escarpments or scarps. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">Landslide<\/a> scarps, like <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3107\">fault scarps<\/a>, are steep terrain created when movement of the adjacent land exposes a part of the subsurface. The most prominent scarp is the main scarp, which marks the uphill extent of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a>. As the disturbed material moves out of place, a step slope forms and develops a new hillside escarpment for the undisturbed material. Main scarps are formed by movement of the displaced material away from the undisturbed ground and are the visible part of slide rupture surface.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"h5p-69\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-69\" class=\"h5p-iframe\" data-content-id=\"69\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"10.4 Identifying Landslide Features\"><\/iframe><\/div>\n<\/div>\n<figure id=\"attachment_4401\" aria-describedby=\"caption-attachment-4401\" style=\"width: 150px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10.3-Rotational-Landslide-QR-Code.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-thumbnail wp-image-678\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Rotational-Landslide-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Rotational-Landslide-QR-Code-150x150.png 150w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Rotational-Landslide-QR-Code-300x300.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Rotational-Landslide-QR-Code-1024x1024.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Rotational-Landslide-QR-Code-768x768.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Rotational-Landslide-QR-Code-65x65.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Rotational-Landslide-QR-Code-225x225.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Rotational-Landslide-QR-Code-350x350.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Rotational-Landslide-QR-Code.png 1147w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a><figcaption id=\"caption-attachment-4401\" class=\"wp-caption-text\">If you are using the printed version of this OER, access this interactive activity via this QR Code.<\/figcaption><\/figure>\n<p>The slide rupture surface is the boundary of the body of movement of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a>. The geologic material below the slide surface does not move, and is marked on the sides by the flanks of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> and at the end by the toe of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a>.<\/p>\n<p>The toe of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> marks the end of the moving material. The toe marks the runout, or maximum distance traveled, of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a>. In rotational <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a>, the toe is often a large, disturbed mound of geologic material, forming as the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> moves past its original rupture surface.<\/p>\n<p>Rotational and translational <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> often have <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1445\">extensional<\/a> cracks, sag ponds, hummocky terrain and pressure ridges. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1445\">Extensional<\/a> cracks form when a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a>\u2019s toe moves forward faster than the rest of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a>, resulting in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1445\">tensional<\/a> forces. Sag ponds are small bodies of water filling depressions formed where <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> movement has impounded <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3130\">drainage<\/a>. Hummocky terrain is undulating and uneven topography that results from the ground being disturbed. Pressure ridges develop on the margins of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> where material is forced upward into a ridge structure.<\/p>\n<h3>Take this quiz to check your comprehension of this section.<\/h3>\n<div id=\"h5p-70\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-70\" class=\"h5p-iframe\" data-content-id=\"70\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"10.3 Did I Get It?\"><\/iframe><\/div>\n<\/div>\n<figure id=\"attachment_4434\" aria-describedby=\"caption-attachment-4434\" style=\"width: 150px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10..3-Did-I-Get-It-QR-Code.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-thumbnail wp-image-679\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Did-I-Get-It-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Did-I-Get-It-QR-Code-150x150.png 150w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Did-I-Get-It-QR-Code-300x300.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Did-I-Get-It-QR-Code-1024x1024.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Did-I-Get-It-QR-Code-768x768.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Did-I-Get-It-QR-Code-65x65.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Did-I-Get-It-QR-Code-225x225.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Did-I-Get-It-QR-Code-350x350.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.3-Did-I-Get-It-QR-Code.png 1147w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a><figcaption id=\"caption-attachment-4434\" class=\"wp-caption-text\">If you are using the printed version of this OER, access the quiz for section 10.3 via this QR Code.<\/figcaption><\/figure>\n<h2><span style=\"font-weight: 400\">10.4 Examples of Landslides<\/span><\/h2>\n<h4><span style=\"font-weight: 400\">Landslides in United States<\/span><\/h4>\n<figure id=\"attachment_3396\" aria-describedby=\"caption-attachment-3396\" style=\"width: 444px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/DSC_0048-1.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-680\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0048-1-300x200.jpg\" alt=\"Scar of the Gros Ventre landslide in background with landslide deposits in the foreground.\" width=\"444\" height=\"296\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0048-1-300x200.jpg 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0048-1-768x512.jpg 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0048-1-65x43.jpg 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0048-1-225x150.jpg 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0048-1-350x233.jpg 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0048-1.jpg 981w\" sizes=\"auto, (max-width: 444px) 100vw, 444px\" \/><\/a><figcaption id=\"caption-attachment-3396\" class=\"wp-caption-text\">Scar of the Gros Ventre landslide in background with landslide deposits in the foreground.<\/figcaption><\/figure>\n<p><b>1925, Gros Ventre, Wyoming:<\/b><span style=\"font-weight: 400\"> On June 23, 1925, a 38 million cubic meter (50 million cu yd) translational rock slide occurred next to the Gros Ventre <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">River<\/a> (pronounced \u201cgrow vont\u201d) near Jackson Hole, Wyoming. Large boulders dammed the Gros Ventre <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">River<\/a> and ran up the opposite side of the valley several hundred vertical feet. The dammed <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">river<\/a> created Slide Lake, and two years later in 1927, lake levels rose high enough to destabilize the dam. The dam failed and caused a catastrophic flood that killed six people in the small downstream community of Kelly, Wyoming. <\/span><\/p>\n<figure id=\"attachment_3397\" aria-describedby=\"caption-attachment-3397\" style=\"width: 550px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.4_Gros_Ventre-Cross-section.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-681 size-full\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Gros_Ventre-Cross-section.jpg\" alt=\"Shows a before and after scenario of the Gros Ventre slide area with bedding parallel to the surface and oversteepending caused by the river. The &quot;after&quot; image show how the rock material slide along a bedding plane.\" width=\"550\" height=\"349\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Gros_Ventre-Cross-section.jpg 550w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Gros_Ventre-Cross-section-300x190.jpg 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Gros_Ventre-Cross-section-65x41.jpg 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Gros_Ventre-Cross-section-225x143.jpg 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Gros_Ventre-Cross-section-350x222.jpg 350w\" sizes=\"auto, (max-width: 550px) 100vw, 550px\" \/><\/a><figcaption id=\"caption-attachment-3397\" class=\"wp-caption-text\">Cross-section of 1925 Gros Ventre slide showing sedimentary layers parallel with the surface and undercutting (oversteepening) of the slope by the river.<\/figcaption><\/figure>\n<p><span style=\"font-weight: 400\">A combination of three factors caused the rock slide: 1) heavy rains and rapidly melting snow <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2706\">saturated<\/a> the Tensleep <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2834\">Sandstone<\/a> causing the underlying <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2839\">shale<\/a> of the Amsden <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2960\">Formation<\/a> to lose its <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3114\">shear strength<\/a>, 2) the Gros Ventre <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">River<\/a> cut through the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2834\">sandstone<\/a> creating an <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3118\">oversteepened<\/a> slope, and 3) soil on top of the mountain became saturated with water due to poor <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3130\">drainage<\/a>. <\/span><span style=\"font-weight: 400\">The cross-section diagram shows how the parallel <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2857\">bedding<\/a> planes between the Tensleep <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2834\">Sandstone<\/a> and Amsden <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2960\">Formation<\/a> offered little friction against the slope surface as the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">river<\/a> undercut the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2834\">sandstone<\/a>. Lastly, the rockslide may have been triggered by an earthquake.<br \/>\n<\/span><\/p>\n<p><b>1959, Madison Canyon, Montana:<\/b><span style=\"font-weight: 400\"> In 1959, the largest earthquake in Rocky Mountain recorded history, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3098\">magnitude<\/a> 7.5, struck the Hebgen Lake, Montana area, causing a destructive seiche on the lake (see <a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/9-crustal-deformation-and-earthquakes\/\">Chapter 9<\/a>). The earthquake caused a rock avalanche that dammed the Madison <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">River<\/a>, creating Quake Lake, and ran up the other side of the valley hundreds of vertical feet. Today, there are still house-sized boulders visible on the slope opposite their starting point. The slide moved at a velocity of up to 160.9 kph (100 mph), creating an incredible air blast that swept through the Rock Creek Campground. The slide killed 28 people, most of whom were in the campground and remain buried there. In a manner like the Gros Ventre slide, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2924\">foliation<\/a> planes of weakness in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2684\">metamorphic rock<\/a> outcrops were parallel with the surface, compromising <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3114\">shear strength<\/a>.<\/span><\/p>\n<figure id=\"attachment_3398\" aria-describedby=\"caption-attachment-3398\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/DSC_0445-DSC_0454_blended_fused-e1491189091595.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-682\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0445-DSC_0454_blended_fused-e1491189091595-1024x361.png\" alt=\"1959 Madison Canyon landslide scar. Photo taken from landslide material.\" width=\"1024\" height=\"361\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0445-DSC_0454_blended_fused-e1491189091595-1024x361.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0445-DSC_0454_blended_fused-e1491189091595-300x106.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0445-DSC_0454_blended_fused-e1491189091595-768x271.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0445-DSC_0454_blended_fused-e1491189091595-1536x541.png 1536w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0445-DSC_0454_blended_fused-e1491189091595-2048x722.png 2048w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0445-DSC_0454_blended_fused-e1491189091595-65x23.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0445-DSC_0454_blended_fused-e1491189091595-225x79.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/DSC_0445-DSC_0454_blended_fused-e1491189091595-350x123.png 350w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><figcaption id=\"caption-attachment-3398\" class=\"wp-caption-text\">1959 Madison Canyon landslide scar. Photo taken from landslide material.<\/figcaption><\/figure>\n<p><strong>1980, Mount Saint Helens, Washington<\/strong>: On May 18, 1980 a 5.1-<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3098\">magnitude<\/a> earthquake triggered the largest <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> observed in the historical record.\u00a0 This <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> was followed by the lateral eruption of Mount Saint Helens <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1181\">volcano<\/a>, and the eruption was followed by <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1181\">volcanic<\/a> <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3123\">debris flows<\/a> known as <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1201\">lahars<\/a>. The volume of material moved by the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> was 2.8 cubic kilometers (0.67 mi<sup>3<\/sup>).<\/p>\n<p><b>1995 and 2005, La Conchita, California: <\/b><span style=\"font-weight: 400\">On March 4, 1995, a fast-moving <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3124\">earthflow<\/a> damaged nine houses in the southern California coastal community of La Conchita. A week later, a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3123\">debris flow<\/a> in the same location damaged five more houses. Surface-<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1445\">tension<\/a> cracks at the top of the slide gave early warning signs in the summer of 1994. During the rainy winter season of 1994\/1995, the cracks grew larger. The likely <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3117\">trigger<\/a> of the 1995 event was unusually heavy rainfall during the winter of 1994\/1995 and rising <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3129\">groundwater<\/a> levels. Ten years later, in 2005, a rapid-<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3123\">debris flow<\/a> occurred at the end of a 15-day <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2192\">period<\/a> of near-record rainfall in southern California. Vegetation remained relatively intact as it was rafted on the surface of the rapid flow, indicating that much of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> mass simply was being carried on a presumably much more <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2706\">saturated<\/a> and fluidized layer beneath. The 2005 slide damaged 36 houses and killed 10 people.<\/span><\/p>\n<figure id=\"attachment_3401\" aria-describedby=\"caption-attachment-3401\" style=\"width: 300px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.4_La_Conchita_oblique-LIDAR.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-683 size-medium\" title=\"Source: Todd Stennett, Airborne 1 Corp., El Segundo. Public domain\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_oblique-LIDAR-300x155.jpg\" alt=\"Image shows many slides in the area instead of just the one.\" width=\"300\" height=\"155\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_oblique-LIDAR-300x155.jpg 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_oblique-LIDAR-1024x530.jpg 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_oblique-LIDAR-768x398.jpg 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_oblique-LIDAR-65x34.jpg 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_oblique-LIDAR-225x117.jpg 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_oblique-LIDAR-350x181.jpg 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_oblique-LIDAR.jpg 1056w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-3401\" class=\"wp-caption-text\">Oblique LIDAR image of La Conchita after the 2005 landslide. Outline of 1995 (blue) and 2005 (yellow) landslides shown; arrows show examples of other landslides in the area; red line outlines main scarp of an ancient landslide for the entire bluff. Source: Todd Stennett, Airborne 1 Corp., El Segundo. Public domain<\/figcaption><\/figure>\n<figure id=\"attachment_3402\" aria-describedby=\"caption-attachment-3402\" style=\"width: 201px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.4_La_Conchita_1995.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-684 size-medium\" title=\"Source: USGS, Public Domain\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_1995-201x300.jpg\" alt=\"Image shows distinct scarp and slide material covering several houses.\" width=\"201\" height=\"300\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_1995-201x300.jpg 201w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_1995-65x97.jpg 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_1995-225x335.jpg 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_1995-350x522.jpg 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_La_Conchita_1995.jpg 451w\" sizes=\"auto, (max-width: 201px) 100vw, 201px\" \/><\/a><figcaption id=\"caption-attachment-3402\" class=\"wp-caption-text\">1995 La Conchita slide. Source: USGS<\/figcaption><\/figure>\n<figure id=\"attachment_3403\" aria-describedby=\"caption-attachment-3403\" style=\"width: 400px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/USGS_MR_Oso_Aerial_clipped_adjusted.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-685\" title=\"Source: USGS, Public Domain\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/USGS_MR_Oso_Aerial_clipped_adjusted.jpg\" alt=\"Photo of large slide debris, flood from dammed river, distinct head scarp.\" width=\"400\" height=\"261\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/USGS_MR_Oso_Aerial_clipped_adjusted.jpg 800w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/USGS_MR_Oso_Aerial_clipped_adjusted-300x195.jpg 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/USGS_MR_Oso_Aerial_clipped_adjusted-768x500.jpg 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/USGS_MR_Oso_Aerial_clipped_adjusted-65x42.jpg 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/USGS_MR_Oso_Aerial_clipped_adjusted-225x147.jpg 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/USGS_MR_Oso_Aerial_clipped_adjusted-350x228.jpg 350w\" sizes=\"auto, (max-width: 400px) 100vw, 400px\" \/><\/a><figcaption id=\"caption-attachment-3403\" class=\"wp-caption-text\">2014 Oso slide in Washington killed 43 people and buried many homes (source: USGS, public domain).<\/figcaption><\/figure>\n<p><b>2014, Oso <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">Landslide<\/a>, Washington:<\/b> On March 22, 2014, a <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> of approximately 18 million tons (10 million yd<sup>3<\/sup>) traveled at 64 kph (40 mph), extended for nearly a 1.6 km (1 m), and dammed the North Fork of the Stillaguamish <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">River<\/a>. The <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> covered 40 homes and killed 43 people in the Steelhead Haven community near Oso, Washington. It produced a volume of material equivalent to 600 football fields covered in material 3 m (10 ft) deep. The winter of 2013-2014 was unusually wet with almost double the average amount of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2707\">precipitation<\/a>. The <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> occurred in an area of the Stillaguamish <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">River<\/a> Valley historically active with many <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a>, but previous events had been small.<\/p>\n<figure id=\"attachment_3404\" aria-describedby=\"caption-attachment-3404\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/JdLC-G_Oso-Landslide-Area-2014-Lidar-Map-scaled.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-3404\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/JdLC-G_Oso-Landslide-Area-2014-Lidar-Map-scaled-1.jpg\" alt=\"Shaded releif map showing size of slide, flow direction arrows, home covered, and distinct scarp.\" width=\"1024\" height=\"663\" \/><\/a><figcaption id=\"caption-attachment-3404\" class=\"wp-caption-text\">Annotated Lidar map of 2014 Oso slide in Washington.<\/figcaption><\/figure>\n<p><b>Yosemite National Park Rock <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">Falls<\/a>:<\/b><span style=\"font-weight: 400\"> The steep cliffs of Yosemite National Park cause frequent rock <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">falls<\/a>. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1934\">Fractures<\/a> created to <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2576\">tectonic<\/a> <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2915\">stresses<\/a> and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1205\">exfoliation<\/a> and expanded by <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1207\">frost wedging<\/a> can cause house-sized blocks of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1962\">granite<\/a> to detach from the cliff-faces of Yosemite National Park.\u00a0 The park models potential runout, the distance <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> material travels, to better assess the risk posed to the millions of park visitors.<br \/>\n<\/span><\/p>\n<figure id=\"attachment_4406\" aria-describedby=\"caption-attachment-4406\" style=\"width: 150px\" class=\"wp-caption alignleft\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/Yosemite-Nature-Notes-Youtube-QR-Code.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-thumbnail wp-image-687\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/Yosemite-Nature-Notes-Youtube-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Yosemite-Nature-Notes-Youtube-QR-Code-150x150.png 150w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Yosemite-Nature-Notes-Youtube-QR-Code-300x300.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Yosemite-Nature-Notes-Youtube-QR-Code-1024x1024.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Yosemite-Nature-Notes-Youtube-QR-Code-768x768.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Yosemite-Nature-Notes-Youtube-QR-Code-65x65.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Yosemite-Nature-Notes-Youtube-QR-Code-225x225.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Yosemite-Nature-Notes-Youtube-QR-Code-350x350.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Yosemite-Nature-Notes-Youtube-QR-Code.png 1155w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a><figcaption id=\"caption-attachment-4406\" class=\"wp-caption-text\">If you are using the printed version of this OER, access this YouTube video via this QR Code.<\/figcaption><\/figure>\n<p><iframe loading=\"lazy\" id=\"oembed-2\" title=\"Yosemite Nature Notes - 10 - Rock Fall\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/H0YhlqP1BgE?feature=oembed&#38;rel=0&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><figcaption><span style=\"color: #333333\"><em><span style=\"font-size: 10pt\"><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\"><em>Rockfalls<\/em><\/a> in Yosemite.<\/span><\/em><\/span><\/figcaption><\/figure>\n<h4><span style=\"font-weight: 400\">Utah Landslides<\/span><\/h4>\n<figure id=\"attachment_3406\" aria-describedby=\"caption-attachment-3406\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/snt45-2_markagunt-megabreccia-map-1030x741-1.gif\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-688\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/snt45-2_markagunt-megabreccia-map-1030x741-1-1024x737.gif\" alt=\"Approximate extent of Markagunt Gravity slide.\" width=\"1024\" height=\"737\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/snt45-2_markagunt-megabreccia-map-1030x741-1-1024x737.gif 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/snt45-2_markagunt-megabreccia-map-1030x741-1-300x216.gif 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/snt45-2_markagunt-megabreccia-map-1030x741-1-768x553.gif 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/snt45-2_markagunt-megabreccia-map-1030x741-1-65x47.gif 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/snt45-2_markagunt-megabreccia-map-1030x741-1-225x162.gif 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/snt45-2_markagunt-megabreccia-map-1030x741-1-350x252.gif 350w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><figcaption id=\"caption-attachment-3406\" class=\"wp-caption-text\">Approximate extent of Markagunt Gravity slide.<\/figcaption><\/figure>\n<p><strong>Markagunt Gravity Slide: <\/strong>About 21\u201322 million years ago, one of the biggest land-based <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> yet discovered in the geologic record displaced more than 1,700 cu km (408 cu mi) of material in one relatively fast event. Evidence for this slide includes breccia <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2833\">conglomerates<\/a> (<a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/5-weathering-erosion-and-sedimentary-rocks\/\">see Chapter 5<\/a>), glassy pseudotachylytes, (<a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/6-metamorphic-rocks\/\">see Chapter 6<\/a>), slip surfaces (similar to <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3065\">faults<\/a>) <a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/9-crustal-deformation-and-earthquakes\/\">see Chapter 9<\/a>), and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1969\">dikes<\/a> (<a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/7-geologic-time\/\">see Chapter 7<\/a>). The <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> is estimated to encompass an area the size of Rhode Island and to extend from near Cedar City, Utah to Panguitch, Utah. This <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> was likely the result of material released from the side of a growing <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1172\">laccolith<\/a> (a type of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2675\">igneous<\/a> intrusion) <a href=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/chapter\/4-igneous-processes-and-volcanoes\/\">see Chapter 4<\/a>), after being triggered by an eruption-related earthquake.<\/p>\n<p>&nbsp;<\/p>\n<figure id=\"attachment_3390\" aria-describedby=\"caption-attachment-3390\" style=\"width: 534px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/Thistlelandslideusgs.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-669\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs.jpg\" alt=\"The 1983 Thistle landslide (foreground) dammed the Spanish Fork river creating a lake.\" width=\"534\" height=\"362\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs.jpg 800w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs-300x204.jpg 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs-768x521.jpg 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs-65x44.jpg 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs-225x153.jpg 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2021\/12\/Thistlelandslideusgs-350x238.jpg 350w\" sizes=\"auto, (max-width: 534px) 100vw, 534px\" \/><\/a><figcaption id=\"caption-attachment-3390\" class=\"wp-caption-text\">The 1983 Thistle landslide (foreground) dammed the Spanish Fork river creating a lake.<\/figcaption><\/figure>\n<p><b>1983, Thistle Slide:<\/b><span style=\"font-weight: 400\">\u00a0<\/span><span style=\"font-weight: 400\">Starting in April of 1983 and continuing into May of that year, a slow-moving <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> traveled 305 m (1,000 ft) downhill and blocked Spanish Fork Canyon with an <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3124\">earthflow<\/a> dam 61 m (200 ft) high. This caused disastrous flooding upstream in the Soldier Creek and Thistle Creek valleys, submerging the town of Thistle. As part of the emergency response, a spillway was constructed to prevent the newly formed lake from breaching the dam. Later, a tunnel was constructed to drain the lake, and currently the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">river<\/a> continues to flow through this tunnel. The rail line and US-6 highway had to be relocated at a cost of more than $200 million.<\/span><\/p>\n<figure id=\"attachment_3407\" aria-describedby=\"caption-attachment-3407\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.4_Rockville1-e1491186191527.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-689\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville1-e1491186191527-1024x442.png\" alt=\"House before and after destruction from 2013 Rockville rockfall.\" width=\"1024\" height=\"442\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville1-e1491186191527-1024x442.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville1-e1491186191527-300x130.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville1-e1491186191527-768x332.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville1-e1491186191527-1536x663.png 1536w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville1-e1491186191527-2048x884.png 2048w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville1-e1491186191527-65x28.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville1-e1491186191527-225x97.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville1-e1491186191527-350x151.png 350w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/a><figcaption id=\"caption-attachment-3407\" class=\"wp-caption-text\">House before and after destruction from 2013 Rockville rockfall.<\/figcaption><\/figure>\n<p><b>2013, Rockville <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">Rock Fall<\/a>:<\/b>Rockville, Utah is a small community near the entrance to Zion National Park. In December of 2013, a 2,700 ton (1,400 yd<sup>3<\/sup>) block of Shinarump <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2833\">Conglomerate<\/a> fell from the Rockville Bench cliff, landed on the steep 35-degree slope below, and shattered into several large pieces that continued downslope at a high speed. These boulders completely destroyed a house located 375 feet below the cliff (see the before and after photographs) and killed two people inside the home. The topographic map shows other rock <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">falls<\/a> in the area prior to this catastrophic event.<\/p>\n<figure id=\"attachment_3409\" aria-describedby=\"caption-attachment-3409\" style=\"width: 487px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/10.4_Rockville2.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-690\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville2-1024x926.png\" alt=\"Tracks of deadly 2013 Rockville rocksfall and earlier documented rockfall events.\" width=\"487\" height=\"440\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville2-1024x926.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville2-300x271.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville2-768x694.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville2-1536x1388.png 1536w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville2-2048x1851.png 2048w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville2-65x59.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville2-225x203.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4_Rockville2-350x316.png 350w\" sizes=\"auto, (max-width: 487px) 100vw, 487px\" \/><\/a><figcaption id=\"caption-attachment-3409\" class=\"wp-caption-text\">Tracks of deadly 2013 Rockville rocksfall and earlier documented rockfall events.<\/figcaption><\/figure>\n<p><b>2014, North Salt Lake Slide:<\/b><span style=\"font-weight: 400\"> In August 2014 after a particularly wet <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2192\">period<\/a>, a slow moving rotational <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> destroyed one home and damaged nearby tennis courts<\/span><span style=\"font-weight: 400\">.<\/span><\/p>\n<figure id=\"attachment_3410\" aria-describedby=\"caption-attachment-3410\" style=\"width: 461px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2021\/12\/RS9196__MG_6439-scaled.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-3410\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/RS9196__MG_6439-scaled-1.jpg\" alt=\"Scarp and displaced material from the North Salt Lake (Parkview) slide of 2014.\" width=\"461\" height=\"323\" \/><\/a><figcaption id=\"caption-attachment-3410\" class=\"wp-caption-text\">Scarp and displaced material from the North Salt Lake (Parkview) slide of 2014.<\/figcaption><\/figure>\n<p><span style=\"font-weight: 400\">Reports from residents suggested that ground cracks had been seen near the top of the slope at least a year prior to the catastrophic movement. <\/span><span style=\"font-weight: 400\">The presence of easily-drained sands and gravels overlying more impermeable clays weathered from <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1181\">volcanic<\/a> <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1949\">ash<\/a>, along with recent regrading of the slope, \u00a0may have been contributing causes of this slide. \u00a0Local heavy rains seem to have provided the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3117\">trigger<\/a>. \u00a0In the two years after the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a>, the slope has been partially regraded to increase its stability. Unfortunately, in January 2017, parts of the slope have shown reactivation movement. Similarly, in 1996 residents in a nearby subdivision started reporting distress to their homes. \u00a0This distress continued until 2012 when 18 homes became uninhabitable due to extensive \u00a0damage and were removed. A geologic park was constructed in the now vacant area.<\/span><\/p>\n<figure id=\"attachment_4405\" aria-describedby=\"caption-attachment-4405\" style=\"width: 150px\" class=\"wp-caption alignleft\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/Time-lapse-video-of-landslide-Youtube-QR-Code.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-thumbnail wp-image-692\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/Time-lapse-video-of-landslide-Youtube-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Time-lapse-video-of-landslide-Youtube-QR-Code-150x150.png 150w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Time-lapse-video-of-landslide-Youtube-QR-Code-300x300.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Time-lapse-video-of-landslide-Youtube-QR-Code-1024x1024.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Time-lapse-video-of-landslide-Youtube-QR-Code-768x768.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Time-lapse-video-of-landslide-Youtube-QR-Code-65x65.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Time-lapse-video-of-landslide-Youtube-QR-Code-225x225.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Time-lapse-video-of-landslide-Youtube-QR-Code-350x350.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Time-lapse-video-of-landslide-Youtube-QR-Code.png 1155w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a><figcaption id=\"caption-attachment-4405\" class=\"wp-caption-text\">If you are using the printed version of this OER, access this YouTube video via this QR Code.<\/figcaption><\/figure>\n<p><iframe loading=\"lazy\" id=\"oembed-3\" title=\"EXCLUSIVE: Time lapse video of landslide in North Salt Lake neighborhood\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/NQs_OWgNshg?feature=oembed&#38;rel=0&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<p><span style=\"color: #333333\"><em><span style=\"font-size: 10pt\">North Salt Lake Landslide<\/span><\/em><\/span><\/p>\n<p><strong>2013, Bingham Canyon Copper <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3324\">Mine<\/a> <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">Landslide<\/a>, Utah:<\/strong> At 9:30 pm on April 10, 2013, more than 65 million cubic meters of steep terraced <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3324\">mine<\/a> wall slid down into the engineered pit of Bingham Canyon <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3324\">mine<\/a>, making it one of the largest historic <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslides<\/a> not associated with <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1181\">volcanoes<\/a>.\u00a0 Radar systems maintained by the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3324\">mine<\/a> operator warned of movement of the wall, preventing the loss of life and limiting the loss of property.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"h5p-71\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-71\" class=\"h5p-iframe\" data-content-id=\"71\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Bingham Canyon Mine\"><\/iframe><\/div>\n<\/div>\n<figure id=\"attachment_4411\" aria-describedby=\"caption-attachment-4411\" style=\"width: 150px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-thumbnail wp-image-693\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code-150x150.png 150w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code-300x300.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code-1024x1024.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code-768x768.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code-65x65.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code-225x225.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code-350x350.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Overview-Bingham-Canyon-Copper-Mine-Landslide-QR-Code.png 1147w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a><figcaption id=\"caption-attachment-4411\" class=\"wp-caption-text\">If you are using the printed version of this OER, access this interactive activity via this QR Code.<\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<h3>Take this quiz to check your comprehension of this section.<\/h3>\n<div id=\"h5p-72\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-72\" class=\"h5p-iframe\" data-content-id=\"72\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"10.4 Did I Get It?\"><\/iframe><\/div>\n<\/div>\n<figure id=\"attachment_4402\" aria-describedby=\"caption-attachment-4402\" style=\"width: 150px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/10.4-Did-I-Get-It-QR-Code.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-thumbnail wp-image-694\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Did-I-Get-It-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Did-I-Get-It-QR-Code-150x150.png 150w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Did-I-Get-It-QR-Code-300x300.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Did-I-Get-It-QR-Code-1024x1024.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Did-I-Get-It-QR-Code-768x768.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Did-I-Get-It-QR-Code-65x65.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Did-I-Get-It-QR-Code-225x225.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Did-I-Get-It-QR-Code-350x350.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/10.4-Did-I-Get-It-QR-Code.png 1147w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a><figcaption id=\"caption-attachment-4402\" class=\"wp-caption-text\">If you are using the printed version of this OER, access the quiz for section 10.4 via this QR Code.<\/figcaption><\/figure>\n<h2><strong>10.5 Chapter Summary<\/strong><\/h2>\n<p><a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">Mass wasting<\/a> is a geologic term describing all downhill rock and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soil<\/a> movement due to gravity. <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3110\">Mass wasting<\/a> occurs when a slope is too steep to remain stable with existing material and conditions. Loose rock and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1203\">soil<\/a>, called <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3111\">regolith<\/a>, are what typically move during a mass-wasting event. Slope stability is determined by two factors: the angle of the slope and the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3114\">shear strength<\/a> of the accumulated materials. Mass-wasting events are triggered by changes that <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3118\">oversteepen<\/a> slope angles and weaken slope stability, such as rapid snow melt, intense rainfall, earthquake shaking, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1181\">volcanic<\/a> eruption, storm waves, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3134\">stream<\/a> <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2677\">erosion<\/a>, and human activities. Excessive <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2707\">precipitation<\/a> is the most common trigger. Mass-wasting events are classified by their type of movement and material, and they share common morphological surface features. The most common types of mass-wasting events are <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">rockfalls<\/a>, slides, flows, and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2447\">creep<\/a>.<\/p>\n<p>Mass-wasting movement ranges from slow to dangerously rapid. Areas with steep topography and rapid rainfall, such as the California <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2890\">coast<\/a>, Rocky Mountain Region, and Pacific Northwest, are particularly susceptible to hazardous mass-wasting events. By examining examples and lessons learned from famous mass-wasting events, scientists have a better understanding of how mass-wasting occurs. This knowledge has brought them closer to predicting where and how these potentially hazardous events may occur and how people can be protected.<\/p>\n<h3>Take this quiz to check your comprehension of this Chapter.<\/h3>\n<div id=\"h5p-73\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-73\" class=\"h5p-iframe\" data-content-id=\"73\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Chapter 10 Review\"><\/iframe><\/div>\n<\/div>\n<figure id=\"attachment_4403\" aria-describedby=\"caption-attachment-4403\" style=\"width: 150px\" class=\"wp-caption aligncenter\"><a href=\"https:\/\/slcc.pressbooks.pub\/app\/uploads\/sites\/35\/2022\/02\/Ch.10-Review-QR-Code.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-thumbnail wp-image-695\" src=\"https:\/\/pressbooks.ccconline.org\/accdigitalmarketing\/wp-content\/uploads\/sites\/222\/2025\/01\/Ch.10-Review-QR-Code-150x150.png\" alt=\"\" width=\"150\" height=\"150\" srcset=\"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Ch.10-Review-QR-Code-150x150.png 150w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Ch.10-Review-QR-Code-300x300.png 300w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Ch.10-Review-QR-Code-1024x1024.png 1024w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Ch.10-Review-QR-Code-768x768.png 768w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Ch.10-Review-QR-Code-65x65.png 65w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Ch.10-Review-QR-Code-225x225.png 225w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Ch.10-Review-QR-Code-350x350.png 350w, https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-content\/uploads\/sites\/222\/2025\/01\/Ch.10-Review-QR-Code.png 1147w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/a><figcaption id=\"caption-attachment-4403\" class=\"wp-caption-text\">If you are using the printed version of this OER, access the review quiz for Chapter 10 via this QR Code.<\/figcaption><\/figure>\n<h2><span style=\"font-weight: 400\">References<\/span><\/h2>\n<div class=\"csl-bib-body\">\n<ol>\n<li class=\"csl-entry\">Haugerud, R.A., 2014, Preliminary interpretation of pre-2014 <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> deposits in the vicinity of Oso, Washington: US Geological Survey.<\/li>\n<li class=\"csl-entry\">Highland, L., 2004, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">Landslide<\/a> types and processes: pubs.er.usgs.gov.<\/li>\n<li class=\"csl-entry\">Highland, L.M., and Bobrowsky, P., 2008, The <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">Landslide<\/a> Handbook &#8211; A Guide to Understanding <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">Landslides<\/a>: U.S. Geological Survey USGS Numbered Series 1325, 147 p.<\/li>\n<li class=\"csl-entry\">Highland, L.M., and Schuster, R.L., 2000, Significant <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> events in the United States: United States Geological Survey.<\/li>\n<li class=\"csl-entry\">Hildenbrand, T.G., and Hendricks, J.D., 1995, Geophysical setting of the Reelfoot <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2624\">rift<\/a> and relations between <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_2624\">rift<\/a> structures and the New Madrid <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3087\">seismic<\/a> zone: U.S. Geological Survey Professional Paper 1538-E, 36 p.<\/li>\n<li class=\"csl-entry\">Hungr, O., Leroueil, S., and Picarelli, L., 2013, The Varnes classification of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">landslide<\/a> types, an update: <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">Landslides<\/a>, v. 11, no. 2, p. 167\u2013194.<\/li>\n<li class=\"csl-entry\">Jibson, R.W., 2005, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_1199\">Landslide<\/a> hazards at La Conchita, California: United States Geological Survey Open-File Report 2005-1067.<\/li>\n<li class=\"csl-entry\">Lipman, P.W., and Mullineaux, D.R., 1981, The 1980 eruptions of Mount St. Helens, Washington: US Geological Survey USGS Numbered Series 1250, 844 p., doi: <a href=\"https:\/\/doi.org\/10.3133\/pp1250\">10.3133\/pp1250<\/a>.<\/li>\n<li class=\"csl-entry\">Lund, W.R., Knudsen, T.R., and Bowman, S.D., 2014, Investigation of the December 12, 2013, Fatal <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_696_3119\">Rock Fall<\/a> at 368 West Main Street, Rockville, Utah: Utah Geological Survey 273, 24 p.<\/li>\n<li class=\"csl-entry\">United States Forest Service, 2016, A Brief History of the Gros Ventre Slide Geological Site: United States Forest Service.<\/li>\n<\/ol>\n<\/div>\n<div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_696_3110\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3110\"><div tabindex=\"-1\"><p>Any downhill movement of material, caused by gravity.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1199\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1199\"><div tabindex=\"-1\"><p>General term for sudden material falling down a slope due to gravity. The term can sometimes cover a wide range of events, including debris flows, rock falls, and mudslides.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1203\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1203\"><div tabindex=\"-1\"><p>A type of non-eroded sediment mixed with organic matter, used by plants. Many essential elements for life, like nitrogen, are delivered to organisms via the soil.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1971\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1971\"><div tabindex=\"-1\"><p>Term for the underlying lithified rocks that make up the geologic record in an area. This term can sometimes refer to only the deeper, crystalline (non-layered) rocks.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3119\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3119\"><div tabindex=\"-1\"><p>Detached, free-falling rocks from very steep slopes.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3123\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3123\"><div tabindex=\"-1\"><p>A mixture of coarse material and water, channeled and flowing downhill rapidly.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2890\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2890\"><div tabindex=\"-1\"><p>The entire area which is related to land-sea interactions.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1447\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1447\"><div tabindex=\"-1\"><p>Stress within an object that causes a side-to-side movement within an internal fabric or weakness.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3112\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3112\"><div tabindex=\"-1\"><p>Component of the gravitational force which pushes material downslope.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3113\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3113\"><div tabindex=\"-1\"><p>Component of the gravitational force which holds material on a slope.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3114\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3114\"><div tabindex=\"-1\"><p>The relationship between shear force and normal force in a block of material on a slope. When shear force is greater than normal force, mass wasting can occur.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3115\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3115\"><div tabindex=\"-1\"><p>Slope angle where shear forces and normal forces are equal.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2828\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2828\"><div tabindex=\"-1\"><p>The average diameter of a grain of sediment, ranging from small, also known as fine-grained (e.g. clay, silt) to large, also known as coarse-grained (e.g. boulder).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2831\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2831\"><div tabindex=\"-1\"><p>The mineral make up of a rock, i.e. which minerals are found within a rock.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3116\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3116\"><div tabindex=\"-1\"><p>Empty space in a geologic material, either within sediments, or within rocks. Can be filled by air, water, or hydrocarbons.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2678\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2678\"><div tabindex=\"-1\"><p>Pieces of rock that have been weathered and possibly eroded.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2857\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2857\"><div tabindex=\"-1\"><p>Discernible layers of rock, typically from a sedimentary rock.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1955\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1955\"><div tabindex=\"-1\"><p>A volcanic rock with medium silica composition, equally rich in felsic minerals (feldspar) and mafic minerals (amphibole, biotite, pyroxene). Intermediate rocks are grey in color and contain somewhat equal amounts of minerals that are light and dark in color. Primary intermediate rocks are andesite (extrusive) and diorite (intrusive).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3375\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3375\"><div tabindex=\"-1\"><\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2839\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2839\"><div tabindex=\"-1\"><p>A very fine-grained rock with very thin layering (fissile).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2706\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2706\"><div tabindex=\"-1\"><p>A solution that has the maximum allowed dissolved component, and is unable to dissolve more.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3117\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3117\"><div tabindex=\"-1\"><p>An event that causes a landslide event. Water is a common trigger.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1181\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1181\"><div tabindex=\"-1\"><p>Place where lava is erupted at the surface.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3134\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3134\"><div tabindex=\"-1\"><p>A channelled body of water.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2677\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2677\"><div tabindex=\"-1\"><p>The transport and movement of weathered sediments.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2862\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2862\"><div tabindex=\"-1\"><p>A sequence of layers in which the sediment changes linearly in size, either getting coarser or finer.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2707\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2707\"><div tabindex=\"-1\"><p>The act of a solid coming out of solution, typically resulting from a drop in temperature or a decrease of the dissolving material.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3127\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3127\"><div tabindex=\"-1\"><p>Water that flows over the surface.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3128\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3128\"><div tabindex=\"-1\"><p>Water that works its way down into the subsurface.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3118\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3118\"><div tabindex=\"-1\"><p>A slope, that by natural or human activity, becomes steeper than the angle of repose.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2207\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2207\"><div tabindex=\"-1\"><p>An exposed part of a craton.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3370\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3370\"><div tabindex=\"-1\"><p>Loose blocks of rock that fall down from steep surfaces and cover slopes.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3121\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3121\"><div tabindex=\"-1\"><p>A landslide that moves a long an internal plane of weakness.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2447\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2447\"><div tabindex=\"-1\"><p>A slow and steady movement. Used with faults, mass wasting in soils, and grain movement.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1934\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1934\"><div tabindex=\"-1\"><p>A break within a rock that has no relative movement between the sides. Caused by cooling, pressure release, tectonic forces, etc.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1204\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1204\"><div tabindex=\"-1\"><p>The physical breakdown (weathering) of bedrock by processes such as pressure, ice expansion, etc.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3120\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3120\"><div tabindex=\"-1\"><p>Movement of regolith along a curved slip plane.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3124\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3124\"><div tabindex=\"-1\"><p>Plastic moving, fine-grained type of flow.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3125\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3125\"><div tabindex=\"-1\"><p>Very slow movement of the soil downhill.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3122\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3122\"><div tabindex=\"-1\"><p>Large and mysterious landslides that travel for long distances.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2868\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2868\"><div tabindex=\"-1\"><p>Ridges of sediment that form perpendicular to flow in the lower part of the lower flow regime.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3372\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3372\"><div tabindex=\"-1\"><p>The measure of degrees north or south from the equator, which has a latitude of 0 degrees.&nbsp; The Earth's north and south poles have latitudes of 90 degrees north and south, respectively.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2679\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2679\"><div tabindex=\"-1\"><p>Sediment gathering together and collecting, typically in a topographic low point.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2651\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2651\"><div tabindex=\"-1\"><p>The act of gathering new information from the senses or from a scientific instrument.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3081\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3081\"><div tabindex=\"-1\"><p>Amount of movement during a faulting event.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3107\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3107\"><div tabindex=\"-1\"><p>Place where fault movement cuts the surface of the Earth.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1445\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1445\"><div tabindex=\"-1\"><p>Stresses that pull objects apart into a larger surface area or volume; stretching forces.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3130\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3130\"><div tabindex=\"-1\"><p>The area within a topographic basin or drainage divide in which water collects.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2834\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2834\"><div tabindex=\"-1\"><p>A rock primarily made of sand.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2960\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2960\"><div tabindex=\"-1\"><p>An extensive, distinct, and mapped set of geologic layers.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3098\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3098\"><div tabindex=\"-1\"><p>A measure of earthquake strength. Scales include Richter and Moment.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2924\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2924\"><div tabindex=\"-1\"><p>A planer alignment of minerals and textures within a rock.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2684\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2684\"><div tabindex=\"-1\"><p>Rocks formed via heat and pressure which change the minerals within the rock.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1201\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1201\"><div tabindex=\"-1\"><p>A type of volcanic mudslide, in which rain or snowmelt accumulates volcanic ash of the slopes of steep volcanoes or other mountains and then wash downhill, causing damaging flooding.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3129\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3129\"><div tabindex=\"-1\"><p>Water that is below the surface.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2192\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2192\"><div tabindex=\"-1\"><p>The third largest span of time recognized by geologists; smaller than a era, larger than a epoch. We are currently in the Quaternary period. Rocks of a specific period are called systems.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2576\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2576\"><div tabindex=\"-1\"><p>The theory that the outer layer of the Earth (the lithosphere) is broken in several plates, and these plates move relative to one another, causing the major topographic features of Earth (e.g. mountains, oceans) and most earthquakes and volcanoes.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2915\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2915\"><div tabindex=\"-1\"><p>Force applied to an object, typically dealing with forces within the Earth.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1205\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1205\"><div tabindex=\"-1\"><p>A type of mechanical weathering in which outer layers of rock, approximately parallel to the surface, fracture off.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1207\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1207\"><div tabindex=\"-1\"><p>A process where water freezes inside cracks in rocks, causing expansion and mechanical weathering.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1962\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1962\"><div tabindex=\"-1\"><p>General name of a felsic rock that is intrusive. Has more felsic minerals than mafic minerals.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2833\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2833\"><div tabindex=\"-1\"><p>A sedimentary rock with rounded, larger (\u22652 mm) clasts.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3065\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3065\"><div tabindex=\"-1\"><p>Planer feature where two blocks of bedrock move past each other via earthquakes.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1969\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1969\"><div tabindex=\"-1\"><p>A narrow igneous intrusion that cuts through existing rock, not along bedding planes.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1172\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1172\"><div tabindex=\"-1\"><p>Large igneous intrusion that is wedged between sedimentary layers, bulging upwards. Called a lopolith if bulging downward.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2675\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2675\"><div tabindex=\"-1\"><p>Rocks that are formed from liquid rock, i.e. from volcanic processes.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_1949\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_1949\"><div tabindex=\"-1\"><p>Volcanic tephra that is less than 2 mm in diameter.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3324\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3324\"><div tabindex=\"-1\"><p>Place where material is extracted from the Earth for human use.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3111\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3111\"><div tabindex=\"-1\"><p>Loose material that is a mixture of soil components and weathered bedrock sediments.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_2624\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_2624\"><div tabindex=\"-1\"><p>Area of extended continental lithosphere, forming a depression. Rifts can be narrow (focused in one place) or broad (spread out over a large area with&nbsp;many faults).<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_696_3087\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_696_3087\"><div tabindex=\"-1\"><p>Energy that radiates from fault movement via earthquakes.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":83,"menu_order":10,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[48],"contributor":[],"license":[],"class_list":["post-696","chapter","type-chapter","status-publish","hentry","chapter-type-numberless"],"part":19,"_links":{"self":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/pressbooks\/v2\/chapters\/696","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/wp\/v2\/users\/83"}],"version-history":[{"count":3,"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/pressbooks\/v2\/chapters\/696\/revisions"}],"predecessor-version":[{"id":3411,"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/pressbooks\/v2\/chapters\/696\/revisions\/3411"}],"part":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/pressbooks\/v2\/parts\/19"}],"metadata":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/pressbooks\/v2\/chapters\/696\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/wp\/v2\/media?parent=696"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/pressbooks\/v2\/chapter-type?post=696"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/wp\/v2\/contributor?post=696"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/accintrogeology\/wp-json\/wp\/v2\/license?post=696"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}