{"id":135,"date":"2024-03-08T22:51:33","date_gmt":"2024-03-08T22:51:33","guid":{"rendered":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/chapter\/physical-weathering\/"},"modified":"2024-03-28T22:18:36","modified_gmt":"2024-03-28T22:18:36","slug":"physical-weathering","status":"publish","type":"chapter","link":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/chapter\/physical-weathering\/","title":{"raw":"Geologic View of Time","rendered":"Geologic View of Time"},"content":{"raw":"<div class=\"physical-weathering\" style=\"text-align: center;\">\r\n<h2>Physical Weathering<\/h2>\r\n<p class=\"import-NormalWeb\">Intrusive igneous rocks form at depths of several hundreds of metres to several tens of kilometres. Sediments are turned into sedimentary rocks only when they are buried by other sediments to depths in excess of several hundreds of metres. Most metamorphic rocks are formed at depths of kilometres to tens of kilometres. Weathering cannot even begin until these rocks are uplifted through various processes of mountain building\u2014most of which are related to plate tectonics\u2014and the overlying material has been eroded away and the rock is exposed as an outcrop. (To a geologist, an outcrop is an exposure of bedrock, the solid rock of the crust.)<\/p>\r\n\r\n<div class=\"textbox shaded\">\r\n<p class=\"import-NormalWeb\"><strong>The most important agents of physical weathering are:<\/strong><\/p>\r\n\r\n<ul>\r\n \t<li class=\"import-Normal\">The decrease in pressure that results from removal of overlying rock<\/li>\r\n \t<li class=\"import-Normal\">Freezing and thawing of water in cracks in the rock<\/li>\r\n \t<li class=\"import-Normal\">Formation of salt crystals within the rock<\/li>\r\n \t<li class=\"import-Normal\">Cracking from plant roots and removal of material by burrowing animals<\/li>\r\n<\/ul>\r\n<\/div>\r\n<p class=\"import-Normal\">When a mass of rock is exposed by weathering and removal of the overlying rock, there is a decrease in the confining pressure on the rock, and the rock expands. This unloading promotes cracking of the rock, known as <strong class=\"import-Strong\">exfoliation<\/strong>, as shown in the granitic rock in <strong>Figure 5.1.1<\/strong>., which, in places, is peeling off like the layers of an onion.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"688\"]<img class=\"\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image1-1.jpeg\" alt=\"Exfoliation fractures in granitic rock exposed on the side of the Coquihalla Highway north of Hope, B.C.\" width=\"688\" height=\"518\" \/> Figure 5.1.1 Exfoliation fractures in granitic rock exposed on the side of the Coquihalla Highway north of Hope, B.C.[\/caption]\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"692\"]<img class=\"\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image2.jpeg\" alt=\"Exfoliation of slate at a road cut in the Columbia Mountains west of Golden, B.C.\" width=\"692\" height=\"308\" \/> Figure 5.1.2 Exfoliation of slate at a road cut in the Columbia Mountains west of Golden, B.C.[\/caption]\r\n<p class=\"import-NormalWeb\">Granitic rock tends to exfoliate parallel to the exposed surface because the rock is typically homogenous, and it doesn\u2019t have predetermined planes along which it must fracture. Sedimentary and metamorphic rocks, on the other hand, tend to exfoliate along predetermined planes (<strong>Figure 5.1.2<\/strong>).<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"402\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image3-1.png\" alt=\"The process of frost wedging on a steep slope shows water in between the cracks of the rocks. \" width=\"402\" height=\"398\" \/> Figure 5.1.3 The process of frost wedging on a steep slope. Water gets into fractures and then freezes, expanding the fracture a little. When the water thaws it seeps a little farther into the expanded crack. The process is repeated many times, and eventually a piece of rock will be wedged away.[\/caption]\r\n<p class=\"import-NormalWeb\">Frost wedging is the process by which water seeps into cracks in a rock, expands on freezing, and thus enlarges the cracks (<strong>Figure 5.1.3<\/strong>). The effectiveness of frost wedging is related to the frequency of freezing and thawing. In warm areas where freezing is infrequent, in very cold areas where thawing is infrequent, or in very dry areas, where there is little water to seep into cracks, the role of frost wedging is limited.<\/p>\r\n<p class=\"import-NormalWeb\">A related process, frost heaving, takes place within unconsolidated materials on gentle slopes. In this case, water in the soil freezes and expands, pushing the overlying material up. Frost heaving is responsible for winter damage to roads all over North America.<\/p>\r\n<p class=\"import-NormalWeb\">When salt water seeps into rocks and then evaporates on a hot sunny day, salt crystals grow within cracks and pores in the rock. The growth of these crystals exerts pressure on the rock and can push grains apart, causing the rock to weaken and break.<\/p>\r\n<p class=\"import-NormalWeb\">The effects of plants and animals are significant in physical weathering. Roots can force their way into even the tiniest cracks, and then they exert tremendous pressure on the rocks as they grow, widening the cracks and breaking the rock (<strong>Figure 5.1.4<\/strong>). Although animals do not normally burrow through solid rock, they can excavate and remove huge volumes of soil, and thus expose the rock to weathering by other mechanisms.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"543\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image4.jpeg\" alt=\"Conifers growing on granitic rocks.\" width=\"543\" height=\"316\" \/> Figure 5.1.4 Conifers growing on granitic rocks at The Lions, near Vancouver, B.C.[\/caption]\r\n<p class=\"import-NormalWeb\">Physical weathering is greatly facilitated by erosion, which is the removal of weathering products, allowing for the exposure of more rock for weathering. On the steep rock faces at the top of the cliff, rock fragments have been broken off by ice wedging, and then removed by gravity. This is a form of mass wasting. Other important agents of erosion that also have the effect of removing the products of weathering include water in streams, glacial ice, and waves on the coasts.<\/p>\r\n\r\n<h2>Chemical Weathering<\/h2>\r\n<p class=\"import-Normal\">Chemical weathering results from chemical changes to minerals that become unstable when they are exposed to surface conditions. The kinds of changes that take place are highly specific to the mineral and the environmental conditions. Some minerals, like quartz, are virtually unaffected by chemical weathering, while others, like feldspar, are easily altered. In general, the degree of chemical weathering is greatest in warm and wet climates, and least in cold and dry climates. The important characteristics of surface conditions that lead to chemical weathering are the presence of water (in the air and on the ground surface), the abundance of oxygen, and the presence of carbon dioxide, which produces weak carbonic acid when combined with water. That process, which is fundamental to most chemical weathering, can be shown as follows:<\/p>\r\n\r\n<div class=\"textbox textbox--exercises\">\r\n<div class=\"textbox__content\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>H<\/strong><sub><strong>2<\/strong><\/sub><strong>O + CO<\/strong><sub><strong>2 <\/strong><\/sub><strong>\u2194\u00a0H<\/strong><sub><strong>2<\/strong><\/sub><strong>CO<\/strong><sub><strong>3\u00a0 \u00a0<\/strong><\/sub>then\u00a0 \u00a0 <strong>H<\/strong><sub><strong>2<\/strong><\/sub><strong>CO<\/strong><sub><strong>3 <\/strong><\/sub><strong>\u2194\u00a0H<\/strong><sup><strong>+<\/strong><\/sup><strong>\u00a0+ HCO<\/strong><sub><strong>3<\/strong><\/sub><sup><strong>\u2212<\/strong><\/sup><\/p>\r\n<p class=\"import-Normal\" style=\"text-align: center;\">water + carbon dioxide <strong>\u2194\u00a0\u00a0<\/strong>carbonic acid<\/p>\r\n<p class=\"import-Normal\" style=\"text-align: center;\">then<\/p>\r\n<p class=\"import-Normal\" style=\"text-align: center;\">carbonic acid\u00a0\u00a0<strong>\u2194<\/strong>\u00a0dissolved hydrogen ions + dissolved bicarbonate ions<\/p>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n<p class=\"import-Normal\"><strong>Yikes! Chemical formulas<\/strong><\/p>\r\n<p class=\"import-Normal\">Lots of people seize up when they are asked to read chemical or mathematical formulas.\u00a0 It\u2019s OK, you don\u2019t necessarily have to!\u00a0 If you don\u2019t like the formulas just read the text underneath them.\u00a0 In time you may get used to reading the formulas.<\/p>\r\n<p class=\"import-Normal\">The double-ended arrow \u201c<strong>\u2194 <\/strong>\u201d indicates that the reaction can go either way, but for our purposes these reactions are going towards the right.<\/p>\r\n<p class=\"import-Normal\">Here we have water (e.g., as rain) plus carbon dioxide in the atmosphere, combining to create carbonic acid. Then carbonic acid dissociates (comes apart) to form hydrogen and bicarbonate ions. The amount of CO<sub>2<\/sub> in the air is enough to make weak carbonic acid.\u00a0 There is typically much more CO<sub>2<\/sub> in the soil, so water that percolates through the soil can become more acidic.\u00a0 In either case, this acidic water is a critical to chemical weathering.<\/p>\r\n<p class=\"import-Normal\">In some types of chemical weathering the original mineral becomes altered to a different mineral. For example, feldspar is altered\u2014by hydrolysis\u2014to form\u00a0clay minerals plus some ions in solution. In other cases the minerals dissolve completely, and their components go into solution. For example, calcite (CaCO<sub>3<\/sub>) is soluble in acidic solutions.<\/p>\r\n<p class=\"import-Normal\">The hydrolysis of feldspar can be written like this:<\/p>\r\n\r\n<div class=\"textbox shaded\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>CaAl<\/strong><sub><strong>2<\/strong><\/sub><strong>Si<\/strong><sub><strong>2<\/strong><\/sub><strong>O<\/strong><sub><strong>8\u00a0 <\/strong><\/sub><strong>+<\/strong><strong> H<\/strong><sub><strong>2<\/strong><\/sub><strong>CO<\/strong><sub><strong>3<\/strong><\/sub><strong>\u00a0 + \u00bdO<\/strong><sub><strong>2<\/strong><\/sub><strong> \u2194 Al<\/strong><sub><strong>2<\/strong><\/sub><strong>Si<\/strong><sub><strong>2<\/strong><\/sub><strong>O<\/strong><sub><strong>5<\/strong><\/sub><strong>(OH)<\/strong><sub><strong>4 <\/strong><\/sub><strong>+<\/strong><strong>Ca<\/strong><sup><strong>2+<\/strong><\/sup><strong> +\u00a0\u00a0CO<\/strong><sub><strong>3<\/strong><\/sub><sup><strong>2\u2212<\/strong><\/sup><\/p>\r\n<p class=\"import-Normal\" style=\"text-align: center;\">plagioclase feldspar + carbonic acid <strong>\u2194 <\/strong>kaolinite + dissolved calcium ions + dissolved carbonate ions<\/p>\r\n\r\n<\/div>\r\n<p class=\"import-Normal\">This reaction shows calcium-bearing plagioclase feldspar, but similar reactions could also be written for sodium or potassium feldspars. In this case, we end up with the mineral kaolinite, along with calcium and carbonate ions in solution. Those ions can eventually combine (probably in the ocean) to form the mineral calcite. The hydrolysis of feldspar to clay is illustrated in<strong> Figure 5.2.1<\/strong>, which shows two images of the same granitic rock, a recently broken fresh surface on the left and a clay-altered weathered surface on the right. Other silicate minerals can also go through hydrolysis, although the end results will be a little different. For example, pyroxene can be converted to the clay minerals chlorite or smectite, and olivine can be converted to the clay mineral serpentine.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"802\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image5.jpeg\" alt=\"Unweathered (left) and weathered (right) surfaces of the same piece of granitic rock.\" width=\"802\" height=\"385\" \/> Figure 5.2.1 Unweathered (left) and weathered (right) surfaces of the same piece of granitic rock. On the unweathered surfaces the feldspars are still fresh and glassy-looking. On the weathered surface much of the feldspar has been altered to the chalky-looking clay mineral kaolinite.[\/caption]\r\n\r\n<\/div>\r\nOxidation is another very important chemical weathering process. The oxidation of the iron in a ferromagnesian silicate starts with the dissolution of the iron. For olivine, the process looks like this, where olivine in the presence of carbonic acid is converted to dissolved iron, carbonate, and silicic acid:\r\n<div class=\"textbox shaded\">\r\n<p style=\"text-align: center;\"><strong><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">Fe<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">2<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">SiO<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">4<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">+ 4H<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">2<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">CO<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript ContextualSpellingAndGrammarErrorV2Themed SCXW97300961 BCX0\" data-fontsize=\"12\">3\u202f\u202f<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun ContextualSpellingAndGrammarErrorV2Themed SCXW97300961 BCX0\">\u2194<\/span><span class=\"NormalTextRun SCXW97300961 BCX0\"> \u202f2Fe<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">2<\/span><span class=\"NormalTextRun Superscript SCXW97300961 BCX0\" data-fontsize=\"12\">+<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">\u202f<\/span><span class=\"NormalTextRun ContextualSpellingAndGrammarErrorV2Themed SCXW97300961 BCX0\">+\u202f 4<\/span><span class=\"NormalTextRun SCXW97300961 BCX0\">HCO<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">3<\/span><span class=\"NormalTextRun Superscript ContextualSpellingAndGrammarErrorV2Themed SCXW97300961 BCX0\" data-fontsize=\"12\">\u2212<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun ContextualSpellingAndGrammarErrorV2Themed SCXW97300961 BCX0\">\u202f +<\/span><span class=\"NormalTextRun SCXW97300961 BCX0\">\u202f H<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">4<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">SiO<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">4<\/span><\/span> <\/strong><\/p>\r\n<p style=\"text-align: center;\"><span class=\"EOP SCXW97300961 BCX0\" data-ccp-props=\"{&quot;201341983&quot;:0,&quot;335551550&quot;:2,&quot;335551620&quot;:2,&quot;335559739&quot;:0,&quot;335559740&quot;:240}\"><span class=\"TextRun SCXW255362036 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW255362036 BCX0\">olivine + (carbonic acid) <\/span><\/span><span class=\"TextRun MacChromeBold SCXW255362036 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW255362036 BCX0\">\u2194 <\/span><\/span><span class=\"TextRun SCXW255362036 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW255362036 BCX0\">dissolved iron ions + dissolved carbonate ions + dissolved silicic acid<\/span><\/span><span class=\"EOP SCXW255362036 BCX0\" data-ccp-props=\"{&quot;201341983&quot;:0,&quot;335551550&quot;:2,&quot;335551620&quot;:2,&quot;335559739&quot;:0,&quot;335559740&quot;:240}\">\u00a0<\/span><\/span><\/p>\r\n\r\n<\/div>\r\n<span style=\"text-align: initial; font-size: 1em;\">But in the presence of oxygen and carbonic acid, the dissolved iron is then quickly converted to the mineral hematite:<\/span>\r\n<div class=\"textbox shaded\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>2Fe<\/strong><sub><strong>2<\/strong><\/sub><sup><strong>+<\/strong><\/sup><strong> \u00a0+<\/strong><strong> 4HCO<\/strong><sub><strong>3<\/strong><\/sub><sup><strong>\u2212<\/strong><\/sup><strong> + \u00bd O<\/strong><sub><strong>2<\/strong><\/sub><strong>\u00a0 +\u00a0 2H<\/strong><sub><strong>2<\/strong><\/sub><strong>O \u2194 Fe<\/strong><sub><strong>2<\/strong><\/sub><strong>O<\/strong><sub><strong>3\u00a0\u00a0 <\/strong><\/sub><strong>+ 4H<\/strong><sub><strong>2<\/strong><\/sub><strong>CO<\/strong><sub><strong>3<\/strong><\/sub><\/p>\r\n<p class=\"import-Normal\" style=\"text-align: center;\">dissolved iron ions + dissolved bicarbonate ions + oxygen + water <strong>\u2194 <\/strong>hematite + carbonic acid<\/p>\r\n\r\n<\/div>\r\n<span style=\"text-align: initial; font-size: 1em;\">The equation shown here is for olivine, but it could apply to almost any other ferromagnesian silicate, including pyroxene, amphibole, or biotite. Iron in the sulphide minerals (e.g., pyrite) can also be oxidized in this way. And the mineral hematite is not the only possible end result, as there is a wide range of iron oxide minerals that can form in this way. The results of this process are illustrated in <\/span><strong style=\"text-align: initial; font-size: 1em;\">Figure 5.2.2<\/strong><span style=\"text-align: initial; font-size: 1em;\">, which shows a granitic rock in which some of the biotite and amphibole have been altered to form the iron oxide mineral limonite.<\/span>\r\n<div class=\"physical-weathering\" style=\"text-align: center;\">\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"482\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image6.jpeg\" alt=\" A granitic rock containing biotite and amphibole. Showing color variations or dark yellow and brown. \" width=\"482\" height=\"385\" \/> Figure 5.2.2 A granitic rock containing biotite and amphibole which have been altered near to the rock\u2019s surface to limonite, which is a mixture of iron oxide minerals.[\/caption]\r\n<p class=\"import-Normal\">A special type of oxidation takes place in areas where the rocks have elevated levels of sulphide minerals, especially pyrite (FeS<sub>2<\/sub>). Pyrite reacts with water and oxygen to form sulphuric acid:<\/p>\r\n\r\n<div class=\"textbox shaded\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>2FeS<\/strong><sub><strong>2\u00a0\u00a0<\/strong><\/sub><strong>+<\/strong><strong> 7O<\/strong><sub><strong>2<\/strong><\/sub><strong>\u00a0+ 2H<\/strong><sub><strong>2<\/strong><\/sub><strong>O \u2194 2Fe<\/strong><sup><strong>2+<\/strong><\/sup><strong>\u00a0\u00a0 H<\/strong><sub><strong>2<\/strong><\/sub><strong>SO<\/strong><sub><strong>4\u00a0<\/strong><\/sub><strong>+ 2H<\/strong><sup><strong>+<\/strong><\/sup><\/p>\r\n<p class=\"import-Normal\" style=\"text-align: center;\">pyrite + oxygen + water <strong>\u2194 <\/strong>dissolved\u00a0iron ions + sulphuric acid + dissolved hydrogen ions<\/p>\r\n\r\n<\/div>\r\n<p class=\"import-Normal\">The hydrolysis of feldspar and other silicate minerals and the oxidation of iron in ferromagnesian silicates all serve to create rocks that are softer and weaker than they were to begin with, and thus more susceptible to physical weathering.<\/p>\r\n<p class=\"import-Normal\">The weathering reactions that we\u2019ve discussed so far involved the transformation of one mineral to another mineral (e.g., feldspar to clay), and the release of some ions in solution (e.g., Ca<sup>2+ <\/sup>or\u00a0Fe<sup>2+<\/sup>). Some weathering processes involve the complete dissolution of a mineral. Calcite, for example, will dissolve in weak acid, to produce calcium and bicarbonate ions. The equation is as follows:<\/p>\r\n\r\n<div class=\"textbox shaded\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>CaCO<\/strong><sub><strong>3<\/strong><\/sub><strong> \u00a0+<\/strong><strong> H<\/strong><sup><strong>+<\/strong><\/sup><strong>\u00a0\u00a0 + HCO<\/strong><sub><strong>3<\/strong><\/sub><sup><strong>\u2212<\/strong><\/sup><strong>\u00a0 \u2194 \u00a0Ca<\/strong><sup><strong>2+<\/strong><\/sup><strong>\u00a0 + 2HCO<\/strong><sub><strong>3<\/strong><\/sub><sup><strong>\u2212<\/strong><\/sup><\/p>\r\n<p class=\"import-Normal\" style=\"text-align: center;\">calcite + dissolved hydrogen ions + dissolved bicarbonate ions <strong>\u2194\u00a0\u00a0<\/strong>dissolved\u00a0\u00a0calcium ions + dissolved bicarbonate ions<\/p>\r\n\r\n<\/div>\r\n<p class=\"import-Normal\">Calcite is the major component of limestone (typically more than 95%), and under surface conditions, limestone can dissolve completely, as shown in <strong>Figure 5.2.4<\/strong>. Limestone also dissolves at relatively shallow depths underground, forming limestone caves.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"455\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image7.jpeg\" alt=\"A limestone outcrop.\" width=\"455\" height=\"439\" \/> Figure 5.2.4 A limestone outcrop on Quadra Island, B.C. The limestone, which is primarily made up of the mineral calcite, has been dissolved to different degrees in different areas because of compositional differences. The buff-coloured bands are chert, which stands out because it is not soluble.[\/caption]\r\n<h2>Deposition<\/h2>\r\n<p class=\"import-NormalWeb\">Sediments accumulate in a wide variety of environments, both on the continents and in the oceans. Some of the more important of these environments are illustrated in <strong>Figure 6.3.1<\/strong>.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"527\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image8.jpeg\" alt=\"Important depositional environments for sediments and sedimentary rocks.\" width=\"527\" height=\"337\" \/> Figure 6.3.1 Some of the important depositional environments for sediments and sedimentary rocks.[\/caption]\r\n<p class=\"import-NormalWeb\">Table 6.4 provides a summary of the processes and sediment types that pertain to the various depositional environments illustrated in <strong>Figure 6.3.1<\/strong>. The characteristics of these various environments, and the processes that take place within them, will be expanded upon when we look at national parks that have glaciation, mass wasting, streams and coasts.<\/p>\r\n&nbsp;\r\n\r\n<strong>Table 6.4 The important terrestrial depositional environments and their characteristics\u200b<\/strong>\r\n<table class=\"aligncenter\" style=\"width: 100%;\" border=\"0.5pt solid windowtext\" cellpadding=\"0.75pt\">\r\n<tbody>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Environment<\/strong><\/p>\r\n<\/th>\r\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Important transport processes<\/strong><\/p>\r\n<\/th>\r\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Depositional environments<\/strong><\/p>\r\n<\/th>\r\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Typical sediment types<\/strong><\/p>\r\n<\/th>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Glacial<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">gravity, moving ice, moving water<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">valleys, plains, streams, lakes<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">glacial till, gravel, sand, silt, and clay<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Alluvial<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">gravity<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">steep-sided valleys<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">coarse angular fragments<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Fluvial<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">moving water<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">streams<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">gravel, sand, silt, and organic matter (in swampy parts only)<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Aeolian<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">wind<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">deserts and coastal regions<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">sand, silt<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Lacustrine<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">moving water (flowing into a lake)<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">lakes<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">sand (near the edges only), silt, clay, and organic matter<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Evaporite<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">moving water\u00a0(flowing into a lake)<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">lakes in arid regions<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">salts, clay<\/p>\r\n<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<strong>Table 6.5 The important marine depositional environments and their characteristics\u200b<\/strong>\r\n<table class=\"aligncenter\" style=\"width: 100%;\" border=\"0.5pt solid windowtext\" cellpadding=\"0.75pt\">\r\n<tbody>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Environment<\/strong><\/p>\r\n<\/th>\r\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Important Transport Processes<\/strong><\/p>\r\n<\/th>\r\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Depositional Environments<\/strong><\/p>\r\n<\/th>\r\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Typical Sediment Types<\/strong><\/p>\r\n<\/th>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Deltaic<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">moving water<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">deltas<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">sand, silt, clay, and organic matter (in swampy parts only)<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Beach<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">waves, longshore currents<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">beaches, spits, sand bars<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">gravel, sand<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Tidal<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">tidal currents<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">tidal flats<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">silt, clay<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Reefs<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">waves and tidal currents<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">reefs and adjacent basins<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">carbonates<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Shallow water marine<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">waves and tidal currents<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">shelves and slopes, lagoons<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">carbonates in tropical climates,\u00a0 sand\/silt\/clay elsewhere<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Lagoonal<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">little transportation<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">lagoon bottom<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">carbonates in tropical climates<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Submarine fan<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">underwater gravity flows<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">continental slopes and abyssal plains<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">gravel, sand, mud<\/p>\r\n<\/td>\r\n<\/tr>\r\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">Deep water marine<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">ocean currents<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">deep-ocean abyssal plains<\/p>\r\n<\/td>\r\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\r\n<p class=\"import-Normal\">clay, carbonate mud, silica mud<\/p>\r\n<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<p class=\"import-NormalWeb\">Most of the sediments that you might see around you, including talus on steep slopes, sand bars in streams, or gravel in road cuts, will never become sedimentary rocks because they have only been deposited relatively recently\u2014perhaps a few centuries or millennia ago\u2014and are likely to be re-eroded before they are buried deep enough beneath other sediments to be lithified. In order for sediments to be preserved long enough to be turned into rock\u2014a process that takes millions or tens of millions of years\u2014they need to have been deposited in a basin that will last that long. Most such basins are formed by plate tectonic processes.<\/p>\r\n\r\n<h2>Stream Erosion and Deposition<\/h2>\r\n<p class=\"import-NormalWeb\">Flowing water is a very important mechanism for erosion, transportation and deposition of sediments. Water flow in a stream is primarily related to the stream\u2019s gradient, but it is also controlled by the geometry of the stream channel. As shown in <strong>Figure 13.3.1<\/strong>, water flow velocity is decreased by friction along the stream bed, so it is slowest at the bottom and edges and fastest near the surface and in the middle. In fact, the velocity just below the surface is typically a little higher than right at the surface because of friction between the water and the air. On a curved section of a stream, flow is fastest on the outside and slowest on the inside.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"854\"]<img class=\"\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image9.png\" alt=\"relative velocity of stream flow when it's straight or curved. \" width=\"854\" height=\"313\" \/> Figure 13.3.1 The relative velocity of stream flow depending on whether the stream channel is straight or curved (left), and with respect to the water depth (right). (Image Description below)[\/caption]\r\n\r\n<div class=\"textbox\">When a stream curves, the flow of water is fastest on the outside of the curve and slowest on the inside of the curve. When the stream is straight and a uniform depth, the stream flows fastest in the middle near the top and slowest along the edges. When the depth is not uniform, the stream flows fastest in the deeper section.<\/div>\r\n<p class=\"import-NormalWeb\">Other factors that affect stream-water velocity are the size of sediments on the stream bed\u2014because large particles tend to slow the flow more than small ones\u2014and the discharge, or volume of water passing a point in a unit of time (e.g., cubic metres (m<sup>3<\/sup>) per second). During a flood, the water level always rises, so there is more cross-sectional area for the water to flow in, however, as long as a river remains confined to its channel, the velocity of the water flow also increases.<\/p>\r\n<p class=\"import-NormalWeb\"><strong>Figure 13.3.2<\/strong> shows the nature of sediment transportation in a stream. Large particles rest on the bottom\u2014bed load\u2014and may only be moved during rapid flows under flood conditions. They can be moved by saltation (bouncing) and by traction (being pushed along by the force of the flow).<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"828\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image10.png\" alt=\"Modes of transportation of sediments and dissolved ions (represented by red dots with + and \u2212 signs) in a stream. \" width=\"828\" height=\"426\" \/> Figure 13.3.2 Modes of transportation of sediments and dissolved ions (represented by red dots with + and \u2212 signs) in a stream.[\/caption]\r\n<p class=\"import-NormalWeb\">Smaller particles may rest on the bottom some of the time, where they can be moved by saltation and traction, but they can also be held in suspension in the flowing water, especially at higher velocities. Streams that flow fast tend to be turbulent (flow paths are chaotic and the water surface appears rough) and the water may be muddy, while those that flow more slowly tend to have laminar flow (straight-line flow and a smooth water surface) and clear water. Turbulent flow is more effective than laminar flow at keeping sediments in suspension.<\/p>\r\n<p class=\"import-NormalWeb\">Stream water also has a dissolved load, which represents (on average) about 15% of the mass of material transported, and includes ions such as calcium (Ca<sup>+2<\/sup>) and chloride (Cl<sup>\u2212<\/sup>) in solution. The solubility of these ions is not affected by flow velocity.<\/p>\r\n<p class=\"import-NormalWeb\">It is important to be aware that a stream can both erode and deposit sediments at the same time. At 100 cm\/s, for example, silt, sand, and medium gravel will be eroded from the stream bed and transported in suspension, coarse gravel will be held in suspension, pebbles will be both transported and deposited, and cobbles and boulders will remain stationary on the stream bed.<\/p>\r\n<p class=\"import-NormalWeb\">A stream typically reaches its greatest velocity when it is close to flooding over its banks. This is known as the bank-full stage, as shown in <strong>Figure 13.3.4<\/strong>. As soon as the flooding stream overtops its banks and occupies the wide area of its flood plain, the water has a much larger area to flow through and the velocity drops significantly. At this point, sediment that was being carried by the high-velocity water is deposited near the edge of the channel, forming a natural bank or lev\u00e9e.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"542\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image11.png\" alt=\"The development of natural lev\u00e9es during flooding of a stream.\" width=\"542\" height=\"470\" \/> Figure 13.3.4 The development of natural lev\u00e9es during flooding of a stream. The sediments of the lev\u00e9e become increasingly fine away from the stream channel, and even finer sediments\u2014clay, silt, and fine sand\u2014are deposited across most of the flood plain.[\/caption]\r\n<h2>Desert Weathering and Erosion<\/h2>\r\n<p class=\"import-NormalWeb\" style=\"background-color: #ffffff;\">\u200cWeathering takes place in desert climates by the same means as other climates, only at a slower rate. While higher temperatures typically spur faster <span class=\"import-glossarylink\">chemical weathering<\/span>, water is the main agent of weathering, and lack of water slows both physical and chemical <span class=\"import-glossarylink\">weathering<\/span>. <span class=\"import-normaltextrun\">Low <\/span><span class=\"import-glossarylink\">precipitation<\/span><span class=\"import-normaltextrun\"> levels also mean less <\/span><span class=\"import-glossarylink\">runoff<\/span><span class=\"import-normaltextrun\">\u00a0as well as <\/span><span class=\"import-glossarylink\">ice wedging<\/span><span class=\"import-normaltextrun\">.\u00a0When\u00a0precipitation\u00a0does occur\u00a0in the desert, it is\u00a0often\u00a0heavy and may result in<\/span> <span class=\"import-glossarylink\">flash floods<\/span> in which a lot of material may be dislodged and moved quickly.<\/p>\r\n<p class=\"import-Normal\">One unique weathering product in deserts is <strong class=\"import-glossarylink\">desert varnish<\/strong>. Also known as desert patina or rock rust, this is thin dark brown layers of clay <span class=\"import-glossarylink\">minerals<\/span> and iron and manganese <span class=\"import-glossarylink\">oxides<\/span> that form on very stable surfaces within arid environments. The exact way this material forms is still unknown, though cosmogenic and biologic mechanisms have been proposed.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"300\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image12.jpeg\" alt=\"Newspaper rock.\" width=\"300\" height=\"200\" \/> Newspaper rock, near Canyonlands National Park, has many petroglyphs carved into desert varnish.[\/caption]\r\n<p class=\"import-NormalWeb\">While water is still the dominant agent of erosion in most desert environments, wind is a notable agent of weathering and <span class=\"import-glossarylink\">erosion<\/span> in many\u00a0deserts. This includes suspended sediment traveling in\u00a0<strong class=\"import-glossarylink\">haboobs<\/strong>, or large dust storms, that frequent deserts. Deposits of windblown dust are called <strong class=\"import-glossarylink\">loess<\/strong>. Loess deposits cover wide areas of the midwestern United States, much of it from rock flour that melted out of the <span class=\"import-glossarylink\">ice sheets<\/span> during the last <span class=\"import-glossarylink\">ice age<\/span>. Loess was also blown from desert regions in the West. Possessing lower energy than water, wind transport nevertheless moves sand, silt, and dust. The load carried by a fluid (air is a fluid like water) is distributed among <span class=\"import-glossarylink\">bedload<\/span> and <span class=\"import-glossarylink\">suspended load<\/span>. As with water, in wind these components depend on wind velocity.<\/p>\r\n<p class=\"import-NormalWeb\">Sand size material moves by a process called <strong class=\"import-glossarylink\">saltation<\/strong> in which sand grains are lifted into the moving air and carried a short distance where they drop and splash into the surface dislodging other sand grains which are then carried a short distance and splash dislodging still others<\/p>\r\n<p class=\"import-NormalWeb\">Saltation is a cascading effect of sand movement creating a zone of wind-blown sand up to a meter or so above the ground. This zone of saltating sand is a powerful erosive agent in which <span class=\"import-glossarylink\">bedrock<\/span> features are effectively sandblasted. The fine-grained suspended load is effectively sorted from the sand near the surface carrying the silt and dust into haboobs. Wind is thus an effective <span class=\"import-glossarylink\">sorting<\/span> agent separating sand and dust sized (\u226470 \u00b5m).\u00a0When wind velocity is high enough to slide or roll materials along the surface, the process is called <strong class=\"import-glossarylink\">creep<\/strong>.<\/p>\r\n<img class=\"alignleft\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image13.jpeg\" alt=\"Sliding stone on flat desert with long trail. \" width=\"272\" height=\"300\" \/>\r\n<p class=\"import-NormalWeb\" style=\"text-align: left;\">One extreme version of sediment movement was shrouded in mystery for years: <strong class=\"import-glossarylink\">Sliding stones<\/strong>. also called sailing stones and sliding rocks, are large boulders that move along flat surfaces in deserts, leaving trails. This includes the famous example of the Racetrack Playa in Death Valley National Park, California. For years, scientists and enthusiasts attempted to explain their movement, with little definitive results. In recent years, several experimental and observational studies have confirmed that the stones, imbedded in thin layers of ice, are propelled by friction from high winds. These studies include measurements of actual movement, as well as re-creations of the conditions, with resulting movement in the lab.<\/p>\r\n<p class=\"import-Normal\" style=\"text-align: left;\"><img class=\"alignright\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image14.jpeg\" alt=\"Yardang with narrow base larger top half. \" width=\"300\" height=\"223\" \/><\/p>\r\n<p class=\"import-NormalWeb\" style=\"text-align: left;\">The zone of saltating sand is an effective agent of erosion through sand abrasion. A bedrock outcrop which has such a sandblasted shape is called a <strong>yardang<\/strong>.<\/p>\r\n&nbsp;\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><img class=\"alignleft\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image15.jpeg\" alt=\"Ventifact with smoother right side of surface and more rough left side of surface. \" width=\"216\" height=\"200\" \/><\/p>\r\n<p class=\"import-Normal\" style=\"text-align: left;\">Rocks and boulders lying on the surface may be blasted and polished by saltating sand. When predominant wind directions shift, multiple sandblasted and polished faces may appear. Such wind abraded desert rocks are called <strong class=\"import-glossarylink\">ventifacts<\/strong><strong class=\"import-glossarylink\">.<\/strong><\/p>\r\n&nbsp;\r\n<p class=\"import-Normal\" style=\"text-align: center;\"><img class=\"alignright\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image16.jpeg\" alt=\"Person standing in the bottom of a blowout. \" width=\"300\" height=\"184\" \/><\/p>\r\n\r\n<\/div>\r\n<span style=\"font-size: 1em;\">Winds may be sufficient to remove materials not anchored by vegetation. The bowl-shaped depression remaining on the surface is called a <\/span><strong class=\"import-glossarylink\" style=\"font-size: 1em;\">blowout<\/strong><span style=\"font-size: 1em;\">.<\/span>\r\n<div class=\"physical-weathering\">\r\n<h2><\/h2>\r\n<h2>Desert Landforms<\/h2>\r\n[caption id=\"\" align=\"alignleft\" width=\"240\"]<img class=\"\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image17.jpeg\" alt=\"Aerial image of alluvial fan in Death Valley.\" width=\"240\" height=\"126\" \/> Aerial image of alluvial fan in Death Valley.[\/caption]\r\n<p class=\"import-Normal\" style=\"text-align: left;\">In the American Southwest, as streams emerge into the valleys from the adjacent mountains, they create desert landforms called alluvial fans. When the stream emerges from the narrow canyon, the flow is no longer constrained by the canyon walls and spreads out. At the lower slope angle, the water slows down and drops its coarser load. As the channel fills with this conglomeratic material, the stream is deflected around it. This deposited material deflects the stream into a system of radial distributary channels in a process similar to how a delta is made by a river entering a body of water. This process develops a system of radial distributaries and constructs a fan shaped feature called an alluvial fan.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignleft\" width=\"263\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image18.jpeg\" alt=\"Bajada along Frisco Peak in Utah.\" width=\"263\" height=\"175\" \/> Bajada along Frisco Peak in Utah.[\/caption]\r\n\r\n[caption id=\"\" align=\"alignright\" width=\"171\"]<img style=\"color: #373d3f; font-weight: bold; font-size: 1em;\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image19.jpeg\" alt=\"Inselbergs in Mojave Desert.\" width=\"171\" height=\"228\" \/> Inselbergs in Mojave Desert.[\/caption]\r\n<p class=\"import-Normal\" style=\"text-align: left;\">Alluvial fans continue to grow and may eventually coalesce with neighboring fans to form an apron of <span class=\"import-glossarylink\">alluvium<\/span> along the mountain front called a <strong>bajada<\/strong>.<\/p>\r\n\r\n<\/div>\r\n<div class=\"physical-weathering\">\r\n<div class=\"mceTemp\"><\/div>\r\n<p class=\"import-Normal\" style=\"text-align: left;\">As the mountains erode away and their sediment accumulates first in <span class=\"import-glossarylink\">alluvial<\/span> fans, then <span class=\"import-glossarylink\">bajadas<\/span>, the mountains eventually are buried in their own erosional debris. Such buried mountain remnants are called <strong class=\"import-glossarylink\">inselbergs<\/strong>, \u201cisland mountains.\u201d<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignright\" width=\"256\"]<img style=\"color: #373d3f; font-weight: bold; font-size: 1em;\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image20.jpeg\" alt=\"Satellite image of desert playa surrounded by mountains.\" width=\"256\" height=\"192\" \/> Satellite image of desert playa surrounded by mountains.[\/caption]\r\n\r\n<\/div>\r\n<div class=\"physical-weathering\">\r\n<div class=\"mceTemp\"><\/div>\r\n<p class=\"import-Normal\" style=\"text-align: left;\">Where the desert valley is an enclosed basin, i.e. streams entering it do not drain out, the water is removed by evaporation and a dry lake <span class=\"import-glossarylink\">bed<\/span> is formed called a <strong>playa.\u00a0<\/strong><\/p>\r\n\r\n<\/div>\r\n<div class=\"physical-weathering\">\r\n\r\n[caption id=\"\" align=\"alignleft\" width=\"282\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image21.jpeg\" alt=\"Dry wash (or ephemeral stream).\" width=\"282\" height=\"170\" \/> Dry wash (or ephemeral stream).[\/caption]\r\n<p class=\"import-Normal\" style=\"text-align: left;\"><span class=\"import-glossarylink\">Playas<\/span> are among the flattest of all landforms. Such a dry lake bed may cover a large area and be filled after a heavy thunderstorm to only a few inches deep. <span class=\"import-glossarylink\">Playa<\/span> lakes and desert <span class=\"import-glossarylink\">streams<\/span> that contain water only after rainstorms are called <strong>intermittent <\/strong>or <strong>ephemeral<\/strong>. <span class=\"import-normaltextrun\">Because of intense thunderstorms, the volume of water transported by <\/span><span class=\"import-glossarylink\">ephemeral<\/span><span class=\"import-normaltextrun\"> drainage\u00a0in arid environments can be substantial during a short <\/span><span class=\"import-glossarylink\">period<\/span><span class=\"import-normaltextrun\"> of time. Desert <\/span><span class=\"import-glossarylink\">soil<\/span><span class=\"import-normaltextrun\"> structures\u00a0lack organic matter that\u00a0promotes <\/span><span class=\"import-glossarylink\">infiltration<\/span><span class=\"import-normaltextrun\">\u00a0by absorbing water.\u00a0Instead of percolating into the soil, the runoff\u00a0compacts the\u00a0ground\u00a0surface, making the soil\u00a0hydrophobic\u00a0or water-repellant. Because of this hardpan surface, <\/span><span class=\"import-glossarylink\">ephemeral streams<\/span><span class=\"import-normaltextrun\"> may gather water\u00a0across\u00a0large areas,\u00a0suddenly filling with water from storms many miles away.<\/span><\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignleft\" width=\"279\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image22.jpeg\" alt=\"Flash flood in a dry wash.\" width=\"279\" height=\"209\" \/> Flash flood in a dry wash.[\/caption]\r\n<p class=\"import-Normal\" style=\"text-align: left;\"><span class=\"import-normaltextrun\">High-volume\u00a0ephemeral\u00a0flows, called\u00a0<\/span><strong class=\"import-normaltextrun\">flash floods<\/strong><span class=\"import-normaltextrun\">,\u00a0may move as sheet flows\u00a0or <\/span><span class=\"import-glossarylink\">sheetwash<\/span><span class=\"import-normaltextrun\">, as well as\u00a0be\u00a0channeled through normally dry <\/span><span class=\"import-glossarylink\">arroyos<\/span><span class=\"import-normaltextrun\"> or canyons.\u00a0Flash floods\u00a0are a major factor in desert\u00a0deposition.\u00a0Dry\u00a0channels\u00a0can\u00a0fill quickly\u00a0with ephemeral <\/span><span class=\"import-glossarylink\">drainage<\/span><span class=\"import-normaltextrun\">, creating\u00a0a mass of water and debris that charges down\u00a0the arroyo,\u00a0and\u00a0even overflowing the banks.\u00a0Flash floods pose\u00a0a serious\u00a0hazard\u00a0for desert travelers\u00a0because the storm activity feeding the runoff may be miles away.\u00a0People\u00a0hiking\u00a0or camping\u00a0in arroyos\u00a0that have been bone dry for months, or years,\u00a0have been swept away by sudden\u00a0<\/span><span class=\"import-glossarylink\">flash floods<\/span><span class=\"import-normaltextrun\">.<\/span><\/p>\r\n\r\n<h2>Dune Types<\/h2>\r\n<p class=\"import-NormalWeb\">Dunes are complex features formed by a combination of wind direction and sand supply, in some cases interacting with vegetation. There are several types of <span class=\"import-glossarylink\">dunes<\/span> representing variables of wind direction, sand supply and vegetative anchoring. <strong>Barchan dunes <\/strong>or <strong>crescent dunes<\/strong> form where sand supply is limited and there is a fairly constant wind direction. Barchans move downwind and develop a crescent shape with wings on either side of a <span class=\"import-glossarylink\">dune<\/span> crest. \u00a0Barchans are known to actually move over homes, even towns.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignleft\" width=\"216\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image23.jpeg\" alt=\"Satellite image of longitudinal dunes in Egypt.\" width=\"216\" height=\"144\" \/> Satellite image of longitudinal dunes in Egypt.[\/caption]\r\n<p class=\"import-NormalWeb\" style=\"text-align: left;\"><strong class=\"import-glossarylink\">Longitudinal dunes <\/strong>or <strong>linear <\/strong><strong class=\"import-glossarylink\">dunes<\/strong> form where sand supply is greater and the wind blows around a dominant direction, in a back-and-forth manner. \u00a0They may form ridges tens of meters high lined up with the predominant wind directions.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignright\" width=\"224\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image24.jpeg\" alt=\"Parabolic dunes, Cape Cod.\" width=\"224\" height=\"219\" \/> Parabolic dunes, Cape Cod.[\/caption]\r\n\r\n&nbsp;\r\n\r\n&nbsp;\r\n<p class=\"import-NormalWeb\" style=\"text-align: left;\"><strong class=\"import-glossarylink\">Parabolic dunes<\/strong> form where vegetation anchors parts of the sand and unanchored parts blowout. \u00a0Parabolic dune shape may be similar to barchan dunes but usually reversed, and it is determined more by the anchoring vegetation than a strict parabolic form.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"alignleft\" width=\"236\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image25.jpeg\" alt=\"Star dune in Sahara.\" width=\"236\" height=\"179\" \/> Star dune in Sahara.[\/caption]\r\n<p class=\"import-NormalWeb\" style=\"text-align: left;\"><strong class=\"import-glossarylink\">Star dunes<\/strong> form where the wind direction is variable in all directions. \u00a0Sand supply can range from limited to quite abundant. \u00a0It is the variation in wind direction that forms the star.<\/p>\r\n\r\n<h2><br style=\"; clear: both;\" \/>Sedimentary Structures<\/h2>\r\n<p class=\"import-NormalWeb\">Through careful observation over the past few centuries, geologists have discovered that the accumulation of sediments and sedimentary rocks takes place according to some important geological principles, as follows:<\/p>\r\n\r\n<ul>\r\n \t<li class=\"import-Normal\">The principle of original horizontality is that sediments accumulate in essentially horizontal layers. The implication is that tilted sedimentary layers observed to day must have been subjected to tectonic forces.<\/li>\r\n \t<li class=\"import-Normal\">The principle of superposition is that sedimentary layers are deposited in sequence, and that unless the entire sequence has been turned over by tectonic processes, the layers at the bottom are older than those at the top.<\/li>\r\n \t<li class=\"import-Normal\">The principle of inclusions is that any rock fragments in a sedimentary layer must be older than the layer. For example, the cobbles in a conglomerate must have been formed before the conglomerate was formed.<\/li>\r\n \t<li class=\"import-Normal\">The principle of faunal succession is that there is a well-defined order in which organisms have evolved through geological time, and therefore the identification of specific fossils in a rock can be used to determine its age.<\/li>\r\n<\/ul>\r\n<p class=\"import-NormalWeb\">In addition to these principles, that apply to all sedimentary rocks (as well as volcanic rocks), a number of other important characteristics of sedimentary processes result in the development of distinctive sedimentary features in specific sedimentary environments. By understanding the origins of these features, we can make some very useful inferences about the processes that led to deposition the rocks that we are studying.<\/p>\r\n<p class=\"import-Normal\">Bedding, for example, is the separation of sediments into layers that either differ from one another in textures, composition, colour, or weathering characteristics, or are separated by partings \u2014narrow gaps between adjacent beds (<strong>Figure 6.4.1<\/strong>). Bedding is an indication of changes in depositional processes that may be related to seasonal differences, changes in climate, changes in locations of rivers or deltas, or tectonic changes. Partings may represent periods of non-deposition that could range from a few decades to a few millennia. Bedding can form in almost any sedimentary depositional environment.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"530\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image26.png\" alt=\"The Triassic Sulphur Mt. Formation near Exshaw, Alberta.\" width=\"530\" height=\"385\" \/> Figure 6.4.1 The Triassic Sulphur Mt. Formation near Exshaw, Alberta. Bedding is defined by differences in colour and texture, and also by partings (gaps) between beds that may otherwise appear to be similar.[\/caption]\r\n<p class=\"import-Normal\">Cross-bedding is bedding that contains angled layers within otherwise horizontal beds, and it forms when sediments are deposited by flowing water or wind. Some examples are shown in <strong>Figures 6.0.11, 6.1.7b<\/strong>, and <strong>6.4.2<\/strong>. Cross-beds formed in streams tend to be on the scale of centimetres to tens of centimetres, while those in aeolian (wind deposited) sediments can be on the scale of metres to several metres.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"588\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image27.png\" alt=\"Cross-bedded Jurassic Navajo Formation aeolian sandstone at Zion National Park, Utah.\" width=\"588\" height=\"440\" \/> Figure 6.4.2 Cross-bedded Jurassic Navajo Formation aeolian sandstone at Zion National Park, Utah. In most of the layers the cross-beds dip down toward the right, implying a consistent wind direction from right to left during deposition.[\/caption]\r\n<p class=\"import-NormalWeb\">Cross-beds form as sediments are deposited on the leading edge of an advancing ripple or dune under steady state conditions (similar flow rate and same flow direction). Each layer is related to a different ripple that advances in the direction of flow, and is partially eroded by the following ripple (<strong>Figure 6.4.3<\/strong>). Cross-bedding is a very important sedimentary structure to be able to recognize because it can provide information on the process of deposition, the direction of current flows and, when analyzed in detail, on other features like the rate of flow and the amount of sediment available.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"1199\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image28.png\" alt=\"Formation of cross-beds as a series of ripples or dunes migrates with the flow.\" width=\"1199\" height=\"329\" \/> Figure 6.4.3 Formation of cross-beds as a series of ripples or dunes migrates with the flow. Each ripple advances forward (right to left in this view) as more sediment is deposited on its leading face (small arrows). (On each ripple the last deposited layer is represented by small dots.)[\/caption]\r\n<p class=\"import-NormalWeb\">Graded bedding is characterized by a gradation in grain size from bottom to top within a single bed. \u201cNormal\u201d graded beds are coarse at the bottom and become finer toward the top.\u00a0 They are a product of deposition from a slowing current (<strong>Figure 6.4.4<\/strong>).\u00a0 Most graded beds form in a submarine-fan environment (see <strong>Figure 6.4.1<\/strong>), where sediment-rich flows descend periodically from a shallow marine shelf down a slope and onto the deeper sea floor.\u00a0Some graded beds are reversed (coarser at the top), and this normally results from deposition by a fast-moving debris flow (see Chapter 15).<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"872\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image29.png\" alt=\"A graded turbidite bed in Cretaceous Spray Formation rocks on Gabriola Island, B.C.\" width=\"872\" height=\"546\" \/> Figure 6.4.4 A graded turbidite bed in Cretaceous Spray Formation rocks on Gabriola Island, B.C. The lower several centimetres of sand and silt probably formed over the duration of less than an hour. The upper few centimetres of fine clay may have accumulated over several hundred years.[\/caption]\r\n<p class=\"import-NormalWeb\">Ripples, which are associated with the formation of cross-bedding, may be preserved on the surfaces of sedimentary beds. Ripples can also help to determine flow direction as they tend to have their steepest surface facing in the direction of the flow (see <strong>Figure 6.4.3<\/strong>).<\/p>\r\n<p class=\"import-NormalWeb\">In a stream environment, boulders, cobbles, and pebbles can become imbricated, meaning that they are generally tilted in the same direction. Clasts in streams tend to tilt with their upper ends pointing downstream because this is the most stable position with respect to the stream flow (<strong>Figure 6.4.5<\/strong> and <strong>Figure 6.1.7c<\/strong>).<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"597\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image30.png\" alt=\"An illustration of imbrication of clasts in a fluvial environment.\" width=\"597\" height=\"279\" \/> Figure 6.4.5 An illustration of imbrication of clasts in a fluvial environment.[\/caption]\r\n<p class=\"import-NormalWeb\">Mud cracks form when a shallow body of water (e.g., a tidal flat or pond or even a puddle), into which muddy sediments have been deposited, dries up and cracks (<strong>Figure 6.4.6<\/strong>). This happens because the clay in the upper mud layer tends to shrink on drying, and so it cracks because it occupies less space when it is dry.<\/p>\r\n\r\n\r\n[caption id=\"\" align=\"aligncenter\" width=\"1135\"]<img src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image31.jpeg\" alt=\"Mudcracks in volcanic mud at a hot-spring area near Myvatn, Iceland.\" width=\"1135\" height=\"683\" \/> Figure 6.4.6 Mudcracks in volcanic mud at a hot-spring area near Myvatn, Iceland.[\/caption]\r\n<p class=\"import-NormalWeb\">The various structures described above are critical to understanding and interpreting the conditions that existed during the formation of sedimentary rocks. We\u2019ll be using this information to explain formations we see in U.S. National Parks today.<\/p>\r\n&nbsp;\r\n<h2><strong>Attributions:<\/strong><\/h2>\r\nModified from<em>: Physical Geology \u2013 2nd Edition by Steven Earle is used under a Creative Commons Attribution 4.0 International Licence.\u00a0 Download for free from the <\/em><a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/\"><em>B.C. Open Collection<\/em><\/a><em>.<\/em>\r\n\r\nModified from: Johnson, Chris , et al. <em>An Introduction to Geology<\/em>. Salt Lake Community College, 2017, opengeology.org\/textbook\/. (Licensed under a <a href=\"http:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License<\/a>.)\r\n\r\nFigure 5.1.1 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a>\r\n\r\nFigure 5.1.2 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a>\r\n\r\nFigure 5.1.3 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a>\r\n\r\nFigure 5.1.4 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a>\r\n\r\nFigure 5.2.1 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a>\r\n\r\nFigure 5.2.2 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a>\r\n\r\nFigure 5.2.4 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a>\r\n\r\nFigure 6.3.1 <a href=\"http:\/\/en.wikipedia.org\/wiki\/Depositional_environment#mediaviewer\/File:SedimentaryEnvironment.jpg\">Schematic diagram showing types of depositional environment<\/a> \u00a9 <a href=\"http:\/\/commons.wikimedia.org\/wiki\/User:Mikenorton\">Mike Norton<\/a>. Adapted by Steven Earle. CC BY-SA.\r\n\r\nFigure 13.3.1 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-13-streams-and-floods\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a>\r\n\r\nFigure 13.3.2 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-13-streams-and-floods\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a>\r\n\r\nFigure 13.3.4 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-13-streams-and-floods\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a>\r\n<p class=\"import-Normal\">Figure 6.4.1 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\r\n<p class=\"import-Normal\">Figure 6.4.2 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\r\n<p class=\"import-Normal\">Figure 6.4.3 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\r\n<p class=\"import-Normal\">Figure 6.4.4 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\r\n<p class=\"import-Normal\">Figure 6.4.5 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\r\n<p class=\"import-Normal\">Figure 6.4.6 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\r\n<p class=\"import-Normal\">Figure 6.4.7 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\r\n\r\n<\/div>","rendered":"<div class=\"physical-weathering\" style=\"text-align: center;\">\n<h2>Physical Weathering<\/h2>\n<p class=\"import-NormalWeb\">Intrusive igneous rocks form at depths of several hundreds of metres to several tens of kilometres. Sediments are turned into sedimentary rocks only when they are buried by other sediments to depths in excess of several hundreds of metres. Most metamorphic rocks are formed at depths of kilometres to tens of kilometres. Weathering cannot even begin until these rocks are uplifted through various processes of mountain building\u2014most of which are related to plate tectonics\u2014and the overlying material has been eroded away and the rock is exposed as an outcrop. (To a geologist, an outcrop is an exposure of bedrock, the solid rock of the crust.)<\/p>\n<div class=\"textbox shaded\">\n<p class=\"import-NormalWeb\"><strong>The most important agents of physical weathering are:<\/strong><\/p>\n<ul>\n<li class=\"import-Normal\">The decrease in pressure that results from removal of overlying rock<\/li>\n<li class=\"import-Normal\">Freezing and thawing of water in cracks in the rock<\/li>\n<li class=\"import-Normal\">Formation of salt crystals within the rock<\/li>\n<li class=\"import-Normal\">Cracking from plant roots and removal of material by burrowing animals<\/li>\n<\/ul>\n<\/div>\n<p class=\"import-Normal\">When a mass of rock is exposed by weathering and removal of the overlying rock, there is a decrease in the confining pressure on the rock, and the rock expands. This unloading promotes cracking of the rock, known as <strong class=\"import-Strong\">exfoliation<\/strong>, as shown in the granitic rock in <strong>Figure 5.1.1<\/strong>., which, in places, is peeling off like the layers of an onion.<\/p>\n<figure style=\"width: 688px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image1-1.jpeg\" alt=\"Exfoliation fractures in granitic rock exposed on the side of the Coquihalla Highway north of Hope, B.C.\" width=\"688\" height=\"518\" \/><figcaption class=\"wp-caption-text\">Figure 5.1.1 Exfoliation fractures in granitic rock exposed on the side of the Coquihalla Highway north of Hope, B.C.<\/figcaption><\/figure>\n<figure style=\"width: 692px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image2.jpeg\" alt=\"Exfoliation of slate at a road cut in the Columbia Mountains west of Golden, B.C.\" width=\"692\" height=\"308\" \/><figcaption class=\"wp-caption-text\">Figure 5.1.2 Exfoliation of slate at a road cut in the Columbia Mountains west of Golden, B.C.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">Granitic rock tends to exfoliate parallel to the exposed surface because the rock is typically homogenous, and it doesn\u2019t have predetermined planes along which it must fracture. Sedimentary and metamorphic rocks, on the other hand, tend to exfoliate along predetermined planes (<strong>Figure 5.1.2<\/strong>).<\/p>\n<figure style=\"width: 402px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image3-1.png\" alt=\"The process of frost wedging on a steep slope shows water in between the cracks of the rocks.\" width=\"402\" height=\"398\" \/><figcaption class=\"wp-caption-text\">Figure 5.1.3 The process of frost wedging on a steep slope. Water gets into fractures and then freezes, expanding the fracture a little. When the water thaws it seeps a little farther into the expanded crack. The process is repeated many times, and eventually a piece of rock will be wedged away.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">Frost wedging is the process by which water seeps into cracks in a rock, expands on freezing, and thus enlarges the cracks (<strong>Figure 5.1.3<\/strong>). The effectiveness of frost wedging is related to the frequency of freezing and thawing. In warm areas where freezing is infrequent, in very cold areas where thawing is infrequent, or in very dry areas, where there is little water to seep into cracks, the role of frost wedging is limited.<\/p>\n<p class=\"import-NormalWeb\">A related process, frost heaving, takes place within unconsolidated materials on gentle slopes. In this case, water in the soil freezes and expands, pushing the overlying material up. Frost heaving is responsible for winter damage to roads all over North America.<\/p>\n<p class=\"import-NormalWeb\">When salt water seeps into rocks and then evaporates on a hot sunny day, salt crystals grow within cracks and pores in the rock. The growth of these crystals exerts pressure on the rock and can push grains apart, causing the rock to weaken and break.<\/p>\n<p class=\"import-NormalWeb\">The effects of plants and animals are significant in physical weathering. Roots can force their way into even the tiniest cracks, and then they exert tremendous pressure on the rocks as they grow, widening the cracks and breaking the rock (<strong>Figure 5.1.4<\/strong>). Although animals do not normally burrow through solid rock, they can excavate and remove huge volumes of soil, and thus expose the rock to weathering by other mechanisms.<\/p>\n<figure style=\"width: 543px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image4.jpeg\" alt=\"Conifers growing on granitic rocks.\" width=\"543\" height=\"316\" \/><figcaption class=\"wp-caption-text\">Figure 5.1.4 Conifers growing on granitic rocks at The Lions, near Vancouver, B.C.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">Physical weathering is greatly facilitated by erosion, which is the removal of weathering products, allowing for the exposure of more rock for weathering. On the steep rock faces at the top of the cliff, rock fragments have been broken off by ice wedging, and then removed by gravity. This is a form of mass wasting. Other important agents of erosion that also have the effect of removing the products of weathering include water in streams, glacial ice, and waves on the coasts.<\/p>\n<h2>Chemical Weathering<\/h2>\n<p class=\"import-Normal\">Chemical weathering results from chemical changes to minerals that become unstable when they are exposed to surface conditions. The kinds of changes that take place are highly specific to the mineral and the environmental conditions. Some minerals, like quartz, are virtually unaffected by chemical weathering, while others, like feldspar, are easily altered. In general, the degree of chemical weathering is greatest in warm and wet climates, and least in cold and dry climates. The important characteristics of surface conditions that lead to chemical weathering are the presence of water (in the air and on the ground surface), the abundance of oxygen, and the presence of carbon dioxide, which produces weak carbonic acid when combined with water. That process, which is fundamental to most chemical weathering, can be shown as follows:<\/p>\n<div class=\"textbox textbox--exercises\">\n<div class=\"textbox__content\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>H<\/strong><sub><strong>2<\/strong><\/sub><strong>O + CO<\/strong><sub><strong>2 <\/strong><\/sub><strong>\u2194\u00a0H<\/strong><sub><strong>2<\/strong><\/sub><strong>CO<\/strong><sub><strong>3\u00a0 \u00a0<\/strong><\/sub>then\u00a0 \u00a0 <strong>H<\/strong><sub><strong>2<\/strong><\/sub><strong>CO<\/strong><sub><strong>3 <\/strong><\/sub><strong>\u2194\u00a0H<\/strong><sup><strong>+<\/strong><\/sup><strong>\u00a0+ HCO<\/strong><sub><strong>3<\/strong><\/sub><sup><strong>\u2212<\/strong><\/sup><\/p>\n<p class=\"import-Normal\" style=\"text-align: center;\">water + carbon dioxide <strong>\u2194\u00a0\u00a0<\/strong>carbonic acid<\/p>\n<p class=\"import-Normal\" style=\"text-align: center;\">then<\/p>\n<p class=\"import-Normal\" style=\"text-align: center;\">carbonic acid\u00a0\u00a0<strong>\u2194<\/strong>\u00a0dissolved hydrogen ions + dissolved bicarbonate ions<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<p class=\"import-Normal\"><strong>Yikes! Chemical formulas<\/strong><\/p>\n<p class=\"import-Normal\">Lots of people seize up when they are asked to read chemical or mathematical formulas.\u00a0 It\u2019s OK, you don\u2019t necessarily have to!\u00a0 If you don\u2019t like the formulas just read the text underneath them.\u00a0 In time you may get used to reading the formulas.<\/p>\n<p class=\"import-Normal\">The double-ended arrow \u201c<strong>\u2194 <\/strong>\u201d indicates that the reaction can go either way, but for our purposes these reactions are going towards the right.<\/p>\n<p class=\"import-Normal\">Here we have water (e.g., as rain) plus carbon dioxide in the atmosphere, combining to create carbonic acid. Then carbonic acid dissociates (comes apart) to form hydrogen and bicarbonate ions. The amount of CO<sub>2<\/sub> in the air is enough to make weak carbonic acid.\u00a0 There is typically much more CO<sub>2<\/sub> in the soil, so water that percolates through the soil can become more acidic.\u00a0 In either case, this acidic water is a critical to chemical weathering.<\/p>\n<p class=\"import-Normal\">In some types of chemical weathering the original mineral becomes altered to a different mineral. For example, feldspar is altered\u2014by hydrolysis\u2014to form\u00a0clay minerals plus some ions in solution. In other cases the minerals dissolve completely, and their components go into solution. For example, calcite (CaCO<sub>3<\/sub>) is soluble in acidic solutions.<\/p>\n<p class=\"import-Normal\">The hydrolysis of feldspar can be written like this:<\/p>\n<div class=\"textbox shaded\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>CaAl<\/strong><sub><strong>2<\/strong><\/sub><strong>Si<\/strong><sub><strong>2<\/strong><\/sub><strong>O<\/strong><sub><strong>8\u00a0 <\/strong><\/sub><strong>+<\/strong><strong> H<\/strong><sub><strong>2<\/strong><\/sub><strong>CO<\/strong><sub><strong>3<\/strong><\/sub><strong>\u00a0 + \u00bdO<\/strong><sub><strong>2<\/strong><\/sub><strong> \u2194 Al<\/strong><sub><strong>2<\/strong><\/sub><strong>Si<\/strong><sub><strong>2<\/strong><\/sub><strong>O<\/strong><sub><strong>5<\/strong><\/sub><strong>(OH)<\/strong><sub><strong>4 <\/strong><\/sub><strong>+<\/strong><strong>Ca<\/strong><sup><strong>2+<\/strong><\/sup><strong> +\u00a0\u00a0CO<\/strong><sub><strong>3<\/strong><\/sub><sup><strong>2\u2212<\/strong><\/sup><\/p>\n<p class=\"import-Normal\" style=\"text-align: center;\">plagioclase feldspar + carbonic acid <strong>\u2194 <\/strong>kaolinite + dissolved calcium ions + dissolved carbonate ions<\/p>\n<\/div>\n<p class=\"import-Normal\">This reaction shows calcium-bearing plagioclase feldspar, but similar reactions could also be written for sodium or potassium feldspars. In this case, we end up with the mineral kaolinite, along with calcium and carbonate ions in solution. Those ions can eventually combine (probably in the ocean) to form the mineral calcite. The hydrolysis of feldspar to clay is illustrated in<strong> Figure 5.2.1<\/strong>, which shows two images of the same granitic rock, a recently broken fresh surface on the left and a clay-altered weathered surface on the right. Other silicate minerals can also go through hydrolysis, although the end results will be a little different. For example, pyroxene can be converted to the clay minerals chlorite or smectite, and olivine can be converted to the clay mineral serpentine.<\/p>\n<figure style=\"width: 802px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image5.jpeg\" alt=\"Unweathered (left) and weathered (right) surfaces of the same piece of granitic rock.\" width=\"802\" height=\"385\" \/><figcaption class=\"wp-caption-text\">Figure 5.2.1 Unweathered (left) and weathered (right) surfaces of the same piece of granitic rock. On the unweathered surfaces the feldspars are still fresh and glassy-looking. On the weathered surface much of the feldspar has been altered to the chalky-looking clay mineral kaolinite.<\/figcaption><\/figure>\n<\/div>\n<p>Oxidation is another very important chemical weathering process. The oxidation of the iron in a ferromagnesian silicate starts with the dissolution of the iron. For olivine, the process looks like this, where olivine in the presence of carbonic acid is converted to dissolved iron, carbonate, and silicic acid:<\/p>\n<div class=\"textbox shaded\">\n<p style=\"text-align: center;\"><strong><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">Fe<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">2<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">SiO<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">4<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">+ 4H<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">2<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">CO<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript ContextualSpellingAndGrammarErrorV2Themed SCXW97300961 BCX0\" data-fontsize=\"12\">3\u202f\u202f<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun ContextualSpellingAndGrammarErrorV2Themed SCXW97300961 BCX0\">\u2194<\/span><span class=\"NormalTextRun SCXW97300961 BCX0\"> \u202f2Fe<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">2<\/span><span class=\"NormalTextRun Superscript SCXW97300961 BCX0\" data-fontsize=\"12\">+<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">\u202f<\/span><span class=\"NormalTextRun ContextualSpellingAndGrammarErrorV2Themed SCXW97300961 BCX0\">+\u202f 4<\/span><span class=\"NormalTextRun SCXW97300961 BCX0\">HCO<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">3<\/span><span class=\"NormalTextRun Superscript ContextualSpellingAndGrammarErrorV2Themed SCXW97300961 BCX0\" data-fontsize=\"12\">\u2212<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun ContextualSpellingAndGrammarErrorV2Themed SCXW97300961 BCX0\">\u202f +<\/span><span class=\"NormalTextRun SCXW97300961 BCX0\">\u202f H<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">4<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW97300961 BCX0\">SiO<\/span><\/span><span class=\"TextRun MacChromeBold SCXW97300961 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun Subscript SCXW97300961 BCX0\" data-fontsize=\"12\">4<\/span><\/span> <\/strong><\/p>\n<p style=\"text-align: center;\"><span class=\"EOP SCXW97300961 BCX0\" data-ccp-props=\"{&quot;201341983&quot;:0,&quot;335551550&quot;:2,&quot;335551620&quot;:2,&quot;335559739&quot;:0,&quot;335559740&quot;:240}\"><span class=\"TextRun SCXW255362036 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW255362036 BCX0\">olivine + (carbonic acid) <\/span><\/span><span class=\"TextRun MacChromeBold SCXW255362036 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW255362036 BCX0\">\u2194 <\/span><\/span><span class=\"TextRun SCXW255362036 BCX0\" lang=\"EN-US\" xml:lang=\"EN-US\" data-contrast=\"auto\"><span class=\"NormalTextRun SCXW255362036 BCX0\">dissolved iron ions + dissolved carbonate ions + dissolved silicic acid<\/span><\/span><span class=\"EOP SCXW255362036 BCX0\" data-ccp-props=\"{&quot;201341983&quot;:0,&quot;335551550&quot;:2,&quot;335551620&quot;:2,&quot;335559739&quot;:0,&quot;335559740&quot;:240}\">\u00a0<\/span><\/span><\/p>\n<\/div>\n<p><span style=\"text-align: initial; font-size: 1em;\">But in the presence of oxygen and carbonic acid, the dissolved iron is then quickly converted to the mineral hematite:<\/span><\/p>\n<div class=\"textbox shaded\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>2Fe<\/strong><sub><strong>2<\/strong><\/sub><sup><strong>+<\/strong><\/sup><strong> \u00a0+<\/strong><strong> 4HCO<\/strong><sub><strong>3<\/strong><\/sub><sup><strong>\u2212<\/strong><\/sup><strong> + \u00bd O<\/strong><sub><strong>2<\/strong><\/sub><strong>\u00a0 +\u00a0 2H<\/strong><sub><strong>2<\/strong><\/sub><strong>O \u2194 Fe<\/strong><sub><strong>2<\/strong><\/sub><strong>O<\/strong><sub><strong>3\u00a0\u00a0 <\/strong><\/sub><strong>+ 4H<\/strong><sub><strong>2<\/strong><\/sub><strong>CO<\/strong><sub><strong>3<\/strong><\/sub><\/p>\n<p class=\"import-Normal\" style=\"text-align: center;\">dissolved iron ions + dissolved bicarbonate ions + oxygen + water <strong>\u2194 <\/strong>hematite + carbonic acid<\/p>\n<\/div>\n<p><span style=\"text-align: initial; font-size: 1em;\">The equation shown here is for olivine, but it could apply to almost any other ferromagnesian silicate, including pyroxene, amphibole, or biotite. Iron in the sulphide minerals (e.g., pyrite) can also be oxidized in this way. And the mineral hematite is not the only possible end result, as there is a wide range of iron oxide minerals that can form in this way. The results of this process are illustrated in <\/span><strong style=\"text-align: initial; font-size: 1em;\">Figure 5.2.2<\/strong><span style=\"text-align: initial; font-size: 1em;\">, which shows a granitic rock in which some of the biotite and amphibole have been altered to form the iron oxide mineral limonite.<\/span><\/p>\n<div class=\"physical-weathering\" style=\"text-align: center;\">\n<figure style=\"width: 482px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image6.jpeg\" alt=\"A granitic rock containing biotite and amphibole. Showing color variations or dark yellow and brown.\" width=\"482\" height=\"385\" \/><figcaption class=\"wp-caption-text\">Figure 5.2.2 A granitic rock containing biotite and amphibole which have been altered near to the rock\u2019s surface to limonite, which is a mixture of iron oxide minerals.<\/figcaption><\/figure>\n<p class=\"import-Normal\">A special type of oxidation takes place in areas where the rocks have elevated levels of sulphide minerals, especially pyrite (FeS<sub>2<\/sub>). Pyrite reacts with water and oxygen to form sulphuric acid:<\/p>\n<div class=\"textbox shaded\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>2FeS<\/strong><sub><strong>2\u00a0\u00a0<\/strong><\/sub><strong>+<\/strong><strong> 7O<\/strong><sub><strong>2<\/strong><\/sub><strong>\u00a0+ 2H<\/strong><sub><strong>2<\/strong><\/sub><strong>O \u2194 2Fe<\/strong><sup><strong>2+<\/strong><\/sup><strong>\u00a0\u00a0 H<\/strong><sub><strong>2<\/strong><\/sub><strong>SO<\/strong><sub><strong>4\u00a0<\/strong><\/sub><strong>+ 2H<\/strong><sup><strong>+<\/strong><\/sup><\/p>\n<p class=\"import-Normal\" style=\"text-align: center;\">pyrite + oxygen + water <strong>\u2194 <\/strong>dissolved\u00a0iron ions + sulphuric acid + dissolved hydrogen ions<\/p>\n<\/div>\n<p class=\"import-Normal\">The hydrolysis of feldspar and other silicate minerals and the oxidation of iron in ferromagnesian silicates all serve to create rocks that are softer and weaker than they were to begin with, and thus more susceptible to physical weathering.<\/p>\n<p class=\"import-Normal\">The weathering reactions that we\u2019ve discussed so far involved the transformation of one mineral to another mineral (e.g., feldspar to clay), and the release of some ions in solution (e.g., Ca<sup>2+ <\/sup>or\u00a0Fe<sup>2+<\/sup>). Some weathering processes involve the complete dissolution of a mineral. Calcite, for example, will dissolve in weak acid, to produce calcium and bicarbonate ions. The equation is as follows:<\/p>\n<div class=\"textbox shaded\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>CaCO<\/strong><sub><strong>3<\/strong><\/sub><strong> \u00a0+<\/strong><strong> H<\/strong><sup><strong>+<\/strong><\/sup><strong>\u00a0\u00a0 + HCO<\/strong><sub><strong>3<\/strong><\/sub><sup><strong>\u2212<\/strong><\/sup><strong>\u00a0 \u2194 \u00a0Ca<\/strong><sup><strong>2+<\/strong><\/sup><strong>\u00a0 + 2HCO<\/strong><sub><strong>3<\/strong><\/sub><sup><strong>\u2212<\/strong><\/sup><\/p>\n<p class=\"import-Normal\" style=\"text-align: center;\">calcite + dissolved hydrogen ions + dissolved bicarbonate ions <strong>\u2194\u00a0\u00a0<\/strong>dissolved\u00a0\u00a0calcium ions + dissolved bicarbonate ions<\/p>\n<\/div>\n<p class=\"import-Normal\">Calcite is the major component of limestone (typically more than 95%), and under surface conditions, limestone can dissolve completely, as shown in <strong>Figure 5.2.4<\/strong>. Limestone also dissolves at relatively shallow depths underground, forming limestone caves.<\/p>\n<figure style=\"width: 455px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image7.jpeg\" alt=\"A limestone outcrop.\" width=\"455\" height=\"439\" \/><figcaption class=\"wp-caption-text\">Figure 5.2.4 A limestone outcrop on Quadra Island, B.C. The limestone, which is primarily made up of the mineral calcite, has been dissolved to different degrees in different areas because of compositional differences. The buff-coloured bands are chert, which stands out because it is not soluble.<\/figcaption><\/figure>\n<h2>Deposition<\/h2>\n<p class=\"import-NormalWeb\">Sediments accumulate in a wide variety of environments, both on the continents and in the oceans. Some of the more important of these environments are illustrated in <strong>Figure 6.3.1<\/strong>.<\/p>\n<figure style=\"width: 527px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image8.jpeg\" alt=\"Important depositional environments for sediments and sedimentary rocks.\" width=\"527\" height=\"337\" \/><figcaption class=\"wp-caption-text\">Figure 6.3.1 Some of the important depositional environments for sediments and sedimentary rocks.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">Table 6.4 provides a summary of the processes and sediment types that pertain to the various depositional environments illustrated in <strong>Figure 6.3.1<\/strong>. The characteristics of these various environments, and the processes that take place within them, will be expanded upon when we look at national parks that have glaciation, mass wasting, streams and coasts.<\/p>\n<p>&nbsp;<\/p>\n<p><strong>Table 6.4 The important terrestrial depositional environments and their characteristics\u200b<\/strong><\/p>\n<table class=\"aligncenter\" style=\"width: 100%;\" cellpadding=\"0.75pt\">\n<tbody>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Environment<\/strong><\/p>\n<\/th>\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Important transport processes<\/strong><\/p>\n<\/th>\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Depositional environments<\/strong><\/p>\n<\/th>\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Typical sediment types<\/strong><\/p>\n<\/th>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Glacial<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">gravity, moving ice, moving water<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">valleys, plains, streams, lakes<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">glacial till, gravel, sand, silt, and clay<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Alluvial<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">gravity<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">steep-sided valleys<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">coarse angular fragments<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Fluvial<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">moving water<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">streams<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">gravel, sand, silt, and organic matter (in swampy parts only)<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Aeolian<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">wind<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">deserts and coastal regions<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">sand, silt<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Lacustrine<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">moving water (flowing into a lake)<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">lakes<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">sand (near the edges only), silt, clay, and organic matter<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Evaporite<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">moving water\u00a0(flowing into a lake)<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">lakes in arid regions<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">salts, clay<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>Table 6.5 The important marine depositional environments and their characteristics\u200b<\/strong><\/p>\n<table class=\"aligncenter\" style=\"width: 100%;\" cellpadding=\"0.75pt\">\n<tbody>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Environment<\/strong><\/p>\n<\/th>\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Important Transport Processes<\/strong><\/p>\n<\/th>\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Depositional Environments<\/strong><\/p>\n<\/th>\n<th class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt; border: 0.5pt solid windowtext;\">\n<p class=\"import-Normal\" style=\"text-align: center;\"><strong>Typical Sediment Types<\/strong><\/p>\n<\/th>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Deltaic<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">moving water<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">deltas<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">sand, silt, clay, and organic matter (in swampy parts only)<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Beach<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">waves, longshore currents<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">beaches, spits, sand bars<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">gravel, sand<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Tidal<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">tidal currents<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">tidal flats<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">silt, clay<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Reefs<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">waves and tidal currents<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">reefs and adjacent basins<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">carbonates<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Shallow water marine<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">waves and tidal currents<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">shelves and slopes, lagoons<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">carbonates in tropical climates,\u00a0 sand\/silt\/clay elsewhere<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Lagoonal<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">little transportation<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">lagoon bottom<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">carbonates in tropical climates<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Submarine fan<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">underwater gravity flows<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">continental slopes and abyssal plains<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">gravel, sand, mud<\/p>\n<\/td>\n<\/tr>\n<tr class=\"TableNormal-R\" style=\"height: 9.75pt;\">\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">Deep water marine<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">ocean currents<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">deep-ocean abyssal plains<\/p>\n<\/td>\n<td class=\"TableNormal-C\" style=\"vertical-align: middle; padding: 0.75pt 0.75pt 0.75pt 0.75pt; border: solid windowtext 0.5pt;\">\n<p class=\"import-Normal\">clay, carbonate mud, silica mud<\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"import-NormalWeb\">Most of the sediments that you might see around you, including talus on steep slopes, sand bars in streams, or gravel in road cuts, will never become sedimentary rocks because they have only been deposited relatively recently\u2014perhaps a few centuries or millennia ago\u2014and are likely to be re-eroded before they are buried deep enough beneath other sediments to be lithified. In order for sediments to be preserved long enough to be turned into rock\u2014a process that takes millions or tens of millions of years\u2014they need to have been deposited in a basin that will last that long. Most such basins are formed by plate tectonic processes.<\/p>\n<h2>Stream Erosion and Deposition<\/h2>\n<p class=\"import-NormalWeb\">Flowing water is a very important mechanism for erosion, transportation and deposition of sediments. Water flow in a stream is primarily related to the stream\u2019s gradient, but it is also controlled by the geometry of the stream channel. As shown in <strong>Figure 13.3.1<\/strong>, water flow velocity is decreased by friction along the stream bed, so it is slowest at the bottom and edges and fastest near the surface and in the middle. In fact, the velocity just below the surface is typically a little higher than right at the surface because of friction between the water and the air. On a curved section of a stream, flow is fastest on the outside and slowest on the inside.<\/p>\n<figure style=\"width: 854px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image9.png\" alt=\"relative velocity of stream flow when it's straight or curved.\" width=\"854\" height=\"313\" \/><figcaption class=\"wp-caption-text\">Figure 13.3.1 The relative velocity of stream flow depending on whether the stream channel is straight or curved (left), and with respect to the water depth (right). (Image Description below)<\/figcaption><\/figure>\n<div class=\"textbox\">When a stream curves, the flow of water is fastest on the outside of the curve and slowest on the inside of the curve. When the stream is straight and a uniform depth, the stream flows fastest in the middle near the top and slowest along the edges. When the depth is not uniform, the stream flows fastest in the deeper section.<\/div>\n<p class=\"import-NormalWeb\">Other factors that affect stream-water velocity are the size of sediments on the stream bed\u2014because large particles tend to slow the flow more than small ones\u2014and the discharge, or volume of water passing a point in a unit of time (e.g., cubic metres (m<sup>3<\/sup>) per second). During a flood, the water level always rises, so there is more cross-sectional area for the water to flow in, however, as long as a river remains confined to its channel, the velocity of the water flow also increases.<\/p>\n<p class=\"import-NormalWeb\"><strong>Figure 13.3.2<\/strong> shows the nature of sediment transportation in a stream. Large particles rest on the bottom\u2014bed load\u2014and may only be moved during rapid flows under flood conditions. They can be moved by saltation (bouncing) and by traction (being pushed along by the force of the flow).<\/p>\n<figure style=\"width: 828px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image10.png\" alt=\"Modes of transportation of sediments and dissolved ions (represented by red dots with + and \u2212 signs) in a stream.\" width=\"828\" height=\"426\" \/><figcaption class=\"wp-caption-text\">Figure 13.3.2 Modes of transportation of sediments and dissolved ions (represented by red dots with + and \u2212 signs) in a stream.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">Smaller particles may rest on the bottom some of the time, where they can be moved by saltation and traction, but they can also be held in suspension in the flowing water, especially at higher velocities. Streams that flow fast tend to be turbulent (flow paths are chaotic and the water surface appears rough) and the water may be muddy, while those that flow more slowly tend to have laminar flow (straight-line flow and a smooth water surface) and clear water. Turbulent flow is more effective than laminar flow at keeping sediments in suspension.<\/p>\n<p class=\"import-NormalWeb\">Stream water also has a dissolved load, which represents (on average) about 15% of the mass of material transported, and includes ions such as calcium (Ca<sup>+2<\/sup>) and chloride (Cl<sup>\u2212<\/sup>) in solution. The solubility of these ions is not affected by flow velocity.<\/p>\n<p class=\"import-NormalWeb\">It is important to be aware that a stream can both erode and deposit sediments at the same time. At 100 cm\/s, for example, silt, sand, and medium gravel will be eroded from the stream bed and transported in suspension, coarse gravel will be held in suspension, pebbles will be both transported and deposited, and cobbles and boulders will remain stationary on the stream bed.<\/p>\n<p class=\"import-NormalWeb\">A stream typically reaches its greatest velocity when it is close to flooding over its banks. This is known as the bank-full stage, as shown in <strong>Figure 13.3.4<\/strong>. As soon as the flooding stream overtops its banks and occupies the wide area of its flood plain, the water has a much larger area to flow through and the velocity drops significantly. At this point, sediment that was being carried by the high-velocity water is deposited near the edge of the channel, forming a natural bank or lev\u00e9e.<\/p>\n<figure style=\"width: 542px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image11.png\" alt=\"The development of natural lev\u00e9es during flooding of a stream.\" width=\"542\" height=\"470\" \/><figcaption class=\"wp-caption-text\">Figure 13.3.4 The development of natural lev\u00e9es during flooding of a stream. The sediments of the lev\u00e9e become increasingly fine away from the stream channel, and even finer sediments\u2014clay, silt, and fine sand\u2014are deposited across most of the flood plain.<\/figcaption><\/figure>\n<h2>Desert Weathering and Erosion<\/h2>\n<p class=\"import-NormalWeb\" style=\"background-color: #ffffff;\">\u200cWeathering takes place in desert climates by the same means as other climates, only at a slower rate. While higher temperatures typically spur faster <span class=\"import-glossarylink\">chemical weathering<\/span>, water is the main agent of weathering, and lack of water slows both physical and chemical <span class=\"import-glossarylink\">weathering<\/span>. <span class=\"import-normaltextrun\">Low <\/span><span class=\"import-glossarylink\">precipitation<\/span><span class=\"import-normaltextrun\"> levels also mean less <\/span><span class=\"import-glossarylink\">runoff<\/span><span class=\"import-normaltextrun\">\u00a0as well as <\/span><span class=\"import-glossarylink\">ice wedging<\/span><span class=\"import-normaltextrun\">.\u00a0When\u00a0precipitation\u00a0does occur\u00a0in the desert, it is\u00a0often\u00a0heavy and may result in<\/span> <span class=\"import-glossarylink\">flash floods<\/span> in which a lot of material may be dislodged and moved quickly.<\/p>\n<p class=\"import-Normal\">One unique weathering product in deserts is <strong class=\"import-glossarylink\">desert varnish<\/strong>. Also known as desert patina or rock rust, this is thin dark brown layers of clay <span class=\"import-glossarylink\">minerals<\/span> and iron and manganese <span class=\"import-glossarylink\">oxides<\/span> that form on very stable surfaces within arid environments. The exact way this material forms is still unknown, though cosmogenic and biologic mechanisms have been proposed.<\/p>\n<figure style=\"width: 300px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image12.jpeg\" alt=\"Newspaper rock.\" width=\"300\" height=\"200\" \/><figcaption class=\"wp-caption-text\">Newspaper rock, near Canyonlands National Park, has many petroglyphs carved into desert varnish.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">While water is still the dominant agent of erosion in most desert environments, wind is a notable agent of weathering and <span class=\"import-glossarylink\">erosion<\/span> in many\u00a0deserts. This includes suspended sediment traveling in\u00a0<strong class=\"import-glossarylink\">haboobs<\/strong>, or large dust storms, that frequent deserts. Deposits of windblown dust are called <strong class=\"import-glossarylink\">loess<\/strong>. Loess deposits cover wide areas of the midwestern United States, much of it from rock flour that melted out of the <span class=\"import-glossarylink\">ice sheets<\/span> during the last <span class=\"import-glossarylink\">ice age<\/span>. Loess was also blown from desert regions in the West. Possessing lower energy than water, wind transport nevertheless moves sand, silt, and dust. The load carried by a fluid (air is a fluid like water) is distributed among <span class=\"import-glossarylink\">bedload<\/span> and <span class=\"import-glossarylink\">suspended load<\/span>. As with water, in wind these components depend on wind velocity.<\/p>\n<p class=\"import-NormalWeb\">Sand size material moves by a process called <strong class=\"import-glossarylink\">saltation<\/strong> in which sand grains are lifted into the moving air and carried a short distance where they drop and splash into the surface dislodging other sand grains which are then carried a short distance and splash dislodging still others<\/p>\n<p class=\"import-NormalWeb\">Saltation is a cascading effect of sand movement creating a zone of wind-blown sand up to a meter or so above the ground. This zone of saltating sand is a powerful erosive agent in which <span class=\"import-glossarylink\">bedrock<\/span> features are effectively sandblasted. The fine-grained suspended load is effectively sorted from the sand near the surface carrying the silt and dust into haboobs. Wind is thus an effective <span class=\"import-glossarylink\">sorting<\/span> agent separating sand and dust sized (\u226470 \u00b5m).\u00a0When wind velocity is high enough to slide or roll materials along the surface, the process is called <strong class=\"import-glossarylink\">creep<\/strong>.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image13.jpeg\" alt=\"Sliding stone on flat desert with long trail.\" width=\"272\" height=\"300\" \/><\/p>\n<p class=\"import-NormalWeb\" style=\"text-align: left;\">One extreme version of sediment movement was shrouded in mystery for years: <strong class=\"import-glossarylink\">Sliding stones<\/strong>. also called sailing stones and sliding rocks, are large boulders that move along flat surfaces in deserts, leaving trails. This includes the famous example of the Racetrack Playa in Death Valley National Park, California. For years, scientists and enthusiasts attempted to explain their movement, with little definitive results. In recent years, several experimental and observational studies have confirmed that the stones, imbedded in thin layers of ice, are propelled by friction from high winds. These studies include measurements of actual movement, as well as re-creations of the conditions, with resulting movement in the lab.<\/p>\n<p class=\"import-Normal\" style=\"text-align: left;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignright\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image14.jpeg\" alt=\"Yardang with narrow base larger top half.\" width=\"300\" height=\"223\" \/><\/p>\n<p class=\"import-NormalWeb\" style=\"text-align: left;\">The zone of saltating sand is an effective agent of erosion through sand abrasion. A bedrock outcrop which has such a sandblasted shape is called a <strong>yardang<\/strong>.<\/p>\n<p>&nbsp;<\/p>\n<p class=\"import-Normal\" style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image15.jpeg\" alt=\"Ventifact with smoother right side of surface and more rough left side of surface.\" width=\"216\" height=\"200\" \/><\/p>\n<p class=\"import-Normal\" style=\"text-align: left;\">Rocks and boulders lying on the surface may be blasted and polished by saltating sand. When predominant wind directions shift, multiple sandblasted and polished faces may appear. Such wind abraded desert rocks are called <strong class=\"import-glossarylink\">ventifacts<\/strong><strong class=\"import-glossarylink\">.<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p class=\"import-Normal\" style=\"text-align: center;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignright\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image16.jpeg\" alt=\"Person standing in the bottom of a blowout.\" width=\"300\" height=\"184\" \/><\/p>\n<\/div>\n<p><span style=\"font-size: 1em;\">Winds may be sufficient to remove materials not anchored by vegetation. The bowl-shaped depression remaining on the surface is called a <\/span><strong class=\"import-glossarylink\" style=\"font-size: 1em;\">blowout<\/strong><span style=\"font-size: 1em;\">.<\/span><\/p>\n<div class=\"physical-weathering\">\n<h2><\/h2>\n<h2>Desert Landforms<\/h2>\n<figure style=\"width: 240px\" class=\"wp-caption alignleft\"><img loading=\"lazy\" decoding=\"async\" class=\"\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image17.jpeg\" alt=\"Aerial image of alluvial fan in Death Valley.\" width=\"240\" height=\"126\" \/><figcaption class=\"wp-caption-text\">Aerial image of alluvial fan in Death Valley.<\/figcaption><\/figure>\n<p class=\"import-Normal\" style=\"text-align: left;\">In the American Southwest, as streams emerge into the valleys from the adjacent mountains, they create desert landforms called alluvial fans. When the stream emerges from the narrow canyon, the flow is no longer constrained by the canyon walls and spreads out. At the lower slope angle, the water slows down and drops its coarser load. As the channel fills with this conglomeratic material, the stream is deflected around it. This deposited material deflects the stream into a system of radial distributary channels in a process similar to how a delta is made by a river entering a body of water. This process develops a system of radial distributaries and constructs a fan shaped feature called an alluvial fan.<\/p>\n<figure style=\"width: 263px\" class=\"wp-caption alignleft\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image18.jpeg\" alt=\"Bajada along Frisco Peak in Utah.\" width=\"263\" height=\"175\" \/><figcaption class=\"wp-caption-text\">Bajada along Frisco Peak in Utah.<\/figcaption><\/figure>\n<figure style=\"width: 171px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" style=\"color: #373d3f; font-weight: bold; font-size: 1em;\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image19.jpeg\" alt=\"Inselbergs in Mojave Desert.\" width=\"171\" height=\"228\" \/><figcaption class=\"wp-caption-text\">Inselbergs in Mojave Desert.<\/figcaption><\/figure>\n<p class=\"import-Normal\" style=\"text-align: left;\">Alluvial fans continue to grow and may eventually coalesce with neighboring fans to form an apron of <span class=\"import-glossarylink\">alluvium<\/span> along the mountain front called a <strong>bajada<\/strong>.<\/p>\n<\/div>\n<div class=\"physical-weathering\">\n<div class=\"mceTemp\"><\/div>\n<p class=\"import-Normal\" style=\"text-align: left;\">As the mountains erode away and their sediment accumulates first in <span class=\"import-glossarylink\">alluvial<\/span> fans, then <span class=\"import-glossarylink\">bajadas<\/span>, the mountains eventually are buried in their own erosional debris. Such buried mountain remnants are called <strong class=\"import-glossarylink\">inselbergs<\/strong>, \u201cisland mountains.\u201d<\/p>\n<figure style=\"width: 256px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" style=\"color: #373d3f; font-weight: bold; font-size: 1em;\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image20.jpeg\" alt=\"Satellite image of desert playa surrounded by mountains.\" width=\"256\" height=\"192\" \/><figcaption class=\"wp-caption-text\">Satellite image of desert playa surrounded by mountains.<\/figcaption><\/figure>\n<\/div>\n<div class=\"physical-weathering\">\n<div class=\"mceTemp\"><\/div>\n<p class=\"import-Normal\" style=\"text-align: left;\">Where the desert valley is an enclosed basin, i.e. streams entering it do not drain out, the water is removed by evaporation and a dry lake <span class=\"import-glossarylink\">bed<\/span> is formed called a <strong>playa.\u00a0<\/strong><\/p>\n<\/div>\n<div class=\"physical-weathering\">\n<figure style=\"width: 282px\" class=\"wp-caption alignleft\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image21.jpeg\" alt=\"Dry wash (or ephemeral stream).\" width=\"282\" height=\"170\" \/><figcaption class=\"wp-caption-text\">Dry wash (or ephemeral stream).<\/figcaption><\/figure>\n<p class=\"import-Normal\" style=\"text-align: left;\"><span class=\"import-glossarylink\">Playas<\/span> are among the flattest of all landforms. Such a dry lake bed may cover a large area and be filled after a heavy thunderstorm to only a few inches deep. <span class=\"import-glossarylink\">Playa<\/span> lakes and desert <span class=\"import-glossarylink\">streams<\/span> that contain water only after rainstorms are called <strong>intermittent <\/strong>or <strong>ephemeral<\/strong>. <span class=\"import-normaltextrun\">Because of intense thunderstorms, the volume of water transported by <\/span><span class=\"import-glossarylink\">ephemeral<\/span><span class=\"import-normaltextrun\"> drainage\u00a0in arid environments can be substantial during a short <\/span><span class=\"import-glossarylink\">period<\/span><span class=\"import-normaltextrun\"> of time. Desert <\/span><span class=\"import-glossarylink\">soil<\/span><span class=\"import-normaltextrun\"> structures\u00a0lack organic matter that\u00a0promotes <\/span><span class=\"import-glossarylink\">infiltration<\/span><span class=\"import-normaltextrun\">\u00a0by absorbing water.\u00a0Instead of percolating into the soil, the runoff\u00a0compacts the\u00a0ground\u00a0surface, making the soil\u00a0hydrophobic\u00a0or water-repellant. Because of this hardpan surface, <\/span><span class=\"import-glossarylink\">ephemeral streams<\/span><span class=\"import-normaltextrun\"> may gather water\u00a0across\u00a0large areas,\u00a0suddenly filling with water from storms many miles away.<\/span><\/p>\n<figure style=\"width: 279px\" class=\"wp-caption alignleft\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image22.jpeg\" alt=\"Flash flood in a dry wash.\" width=\"279\" height=\"209\" \/><figcaption class=\"wp-caption-text\">Flash flood in a dry wash.<\/figcaption><\/figure>\n<p class=\"import-Normal\" style=\"text-align: left;\"><span class=\"import-normaltextrun\">High-volume\u00a0ephemeral\u00a0flows, called\u00a0<\/span><strong class=\"import-normaltextrun\">flash floods<\/strong><span class=\"import-normaltextrun\">,\u00a0may move as sheet flows\u00a0or <\/span><span class=\"import-glossarylink\">sheetwash<\/span><span class=\"import-normaltextrun\">, as well as\u00a0be\u00a0channeled through normally dry <\/span><span class=\"import-glossarylink\">arroyos<\/span><span class=\"import-normaltextrun\"> or canyons.\u00a0Flash floods\u00a0are a major factor in desert\u00a0deposition.\u00a0Dry\u00a0channels\u00a0can\u00a0fill quickly\u00a0with ephemeral <\/span><span class=\"import-glossarylink\">drainage<\/span><span class=\"import-normaltextrun\">, creating\u00a0a mass of water and debris that charges down\u00a0the arroyo,\u00a0and\u00a0even overflowing the banks.\u00a0Flash floods pose\u00a0a serious\u00a0hazard\u00a0for desert travelers\u00a0because the storm activity feeding the runoff may be miles away.\u00a0People\u00a0hiking\u00a0or camping\u00a0in arroyos\u00a0that have been bone dry for months, or years,\u00a0have been swept away by sudden\u00a0<\/span><span class=\"import-glossarylink\">flash floods<\/span><span class=\"import-normaltextrun\">.<\/span><\/p>\n<h2>Dune Types<\/h2>\n<p class=\"import-NormalWeb\">Dunes are complex features formed by a combination of wind direction and sand supply, in some cases interacting with vegetation. There are several types of <span class=\"import-glossarylink\">dunes<\/span> representing variables of wind direction, sand supply and vegetative anchoring. <strong>Barchan dunes <\/strong>or <strong>crescent dunes<\/strong> form where sand supply is limited and there is a fairly constant wind direction. Barchans move downwind and develop a crescent shape with wings on either side of a <span class=\"import-glossarylink\">dune<\/span> crest. \u00a0Barchans are known to actually move over homes, even towns.<\/p>\n<figure style=\"width: 216px\" class=\"wp-caption alignleft\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image23.jpeg\" alt=\"Satellite image of longitudinal dunes in Egypt.\" width=\"216\" height=\"144\" \/><figcaption class=\"wp-caption-text\">Satellite image of longitudinal dunes in Egypt.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\" style=\"text-align: left;\"><strong class=\"import-glossarylink\">Longitudinal dunes <\/strong>or <strong>linear <\/strong><strong class=\"import-glossarylink\">dunes<\/strong> form where sand supply is greater and the wind blows around a dominant direction, in a back-and-forth manner. \u00a0They may form ridges tens of meters high lined up with the predominant wind directions.<\/p>\n<figure style=\"width: 224px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image24.jpeg\" alt=\"Parabolic dunes, Cape Cod.\" width=\"224\" height=\"219\" \/><figcaption class=\"wp-caption-text\">Parabolic dunes, Cape Cod.<\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p class=\"import-NormalWeb\" style=\"text-align: left;\"><strong class=\"import-glossarylink\">Parabolic dunes<\/strong> form where vegetation anchors parts of the sand and unanchored parts blowout. \u00a0Parabolic dune shape may be similar to barchan dunes but usually reversed, and it is determined more by the anchoring vegetation than a strict parabolic form.<\/p>\n<figure style=\"width: 236px\" class=\"wp-caption alignleft\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image25.jpeg\" alt=\"Star dune in Sahara.\" width=\"236\" height=\"179\" \/><figcaption class=\"wp-caption-text\">Star dune in Sahara.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\" style=\"text-align: left;\"><strong class=\"import-glossarylink\">Star dunes<\/strong> form where the wind direction is variable in all directions. \u00a0Sand supply can range from limited to quite abundant. \u00a0It is the variation in wind direction that forms the star.<\/p>\n<h2><br style=\"; clear: both;\" \/>Sedimentary Structures<\/h2>\n<p class=\"import-NormalWeb\">Through careful observation over the past few centuries, geologists have discovered that the accumulation of sediments and sedimentary rocks takes place according to some important geological principles, as follows:<\/p>\n<ul>\n<li class=\"import-Normal\">The principle of original horizontality is that sediments accumulate in essentially horizontal layers. The implication is that tilted sedimentary layers observed to day must have been subjected to tectonic forces.<\/li>\n<li class=\"import-Normal\">The principle of superposition is that sedimentary layers are deposited in sequence, and that unless the entire sequence has been turned over by tectonic processes, the layers at the bottom are older than those at the top.<\/li>\n<li class=\"import-Normal\">The principle of inclusions is that any rock fragments in a sedimentary layer must be older than the layer. For example, the cobbles in a conglomerate must have been formed before the conglomerate was formed.<\/li>\n<li class=\"import-Normal\">The principle of faunal succession is that there is a well-defined order in which organisms have evolved through geological time, and therefore the identification of specific fossils in a rock can be used to determine its age.<\/li>\n<\/ul>\n<p class=\"import-NormalWeb\">In addition to these principles, that apply to all sedimentary rocks (as well as volcanic rocks), a number of other important characteristics of sedimentary processes result in the development of distinctive sedimentary features in specific sedimentary environments. By understanding the origins of these features, we can make some very useful inferences about the processes that led to deposition the rocks that we are studying.<\/p>\n<p class=\"import-Normal\">Bedding, for example, is the separation of sediments into layers that either differ from one another in textures, composition, colour, or weathering characteristics, or are separated by partings \u2014narrow gaps between adjacent beds (<strong>Figure 6.4.1<\/strong>). Bedding is an indication of changes in depositional processes that may be related to seasonal differences, changes in climate, changes in locations of rivers or deltas, or tectonic changes. Partings may represent periods of non-deposition that could range from a few decades to a few millennia. Bedding can form in almost any sedimentary depositional environment.<\/p>\n<figure style=\"width: 530px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image26.png\" alt=\"The Triassic Sulphur Mt. Formation near Exshaw, Alberta.\" width=\"530\" height=\"385\" \/><figcaption class=\"wp-caption-text\">Figure 6.4.1 The Triassic Sulphur Mt. Formation near Exshaw, Alberta. Bedding is defined by differences in colour and texture, and also by partings (gaps) between beds that may otherwise appear to be similar.<\/figcaption><\/figure>\n<p class=\"import-Normal\">Cross-bedding is bedding that contains angled layers within otherwise horizontal beds, and it forms when sediments are deposited by flowing water or wind. Some examples are shown in <strong>Figures 6.0.11, 6.1.7b<\/strong>, and <strong>6.4.2<\/strong>. Cross-beds formed in streams tend to be on the scale of centimetres to tens of centimetres, while those in aeolian (wind deposited) sediments can be on the scale of metres to several metres.<\/p>\n<figure style=\"width: 588px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image27.png\" alt=\"Cross-bedded Jurassic Navajo Formation aeolian sandstone at Zion National Park, Utah.\" width=\"588\" height=\"440\" \/><figcaption class=\"wp-caption-text\">Figure 6.4.2 Cross-bedded Jurassic Navajo Formation aeolian sandstone at Zion National Park, Utah. In most of the layers the cross-beds dip down toward the right, implying a consistent wind direction from right to left during deposition.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">Cross-beds form as sediments are deposited on the leading edge of an advancing ripple or dune under steady state conditions (similar flow rate and same flow direction). Each layer is related to a different ripple that advances in the direction of flow, and is partially eroded by the following ripple (<strong>Figure 6.4.3<\/strong>). Cross-bedding is a very important sedimentary structure to be able to recognize because it can provide information on the process of deposition, the direction of current flows and, when analyzed in detail, on other features like the rate of flow and the amount of sediment available.<\/p>\n<figure style=\"width: 1199px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image28.png\" alt=\"Formation of cross-beds as a series of ripples or dunes migrates with the flow.\" width=\"1199\" height=\"329\" \/><figcaption class=\"wp-caption-text\">Figure 6.4.3 Formation of cross-beds as a series of ripples or dunes migrates with the flow. Each ripple advances forward (right to left in this view) as more sediment is deposited on its leading face (small arrows). (On each ripple the last deposited layer is represented by small dots.)<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">Graded bedding is characterized by a gradation in grain size from bottom to top within a single bed. \u201cNormal\u201d graded beds are coarse at the bottom and become finer toward the top.\u00a0 They are a product of deposition from a slowing current (<strong>Figure 6.4.4<\/strong>).\u00a0 Most graded beds form in a submarine-fan environment (see <strong>Figure 6.4.1<\/strong>), where sediment-rich flows descend periodically from a shallow marine shelf down a slope and onto the deeper sea floor.\u00a0Some graded beds are reversed (coarser at the top), and this normally results from deposition by a fast-moving debris flow (see Chapter 15).<\/p>\n<figure style=\"width: 872px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image29.png\" alt=\"A graded turbidite bed in Cretaceous Spray Formation rocks on Gabriola Island, B.C.\" width=\"872\" height=\"546\" \/><figcaption class=\"wp-caption-text\">Figure 6.4.4 A graded turbidite bed in Cretaceous Spray Formation rocks on Gabriola Island, B.C. The lower several centimetres of sand and silt probably formed over the duration of less than an hour. The upper few centimetres of fine clay may have accumulated over several hundred years.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">Ripples, which are associated with the formation of cross-bedding, may be preserved on the surfaces of sedimentary beds. Ripples can also help to determine flow direction as they tend to have their steepest surface facing in the direction of the flow (see <strong>Figure 6.4.3<\/strong>).<\/p>\n<p class=\"import-NormalWeb\">In a stream environment, boulders, cobbles, and pebbles can become imbricated, meaning that they are generally tilted in the same direction. Clasts in streams tend to tilt with their upper ends pointing downstream because this is the most stable position with respect to the stream flow (<strong>Figure 6.4.5<\/strong> and <strong>Figure 6.1.7c<\/strong>).<\/p>\n<figure style=\"width: 597px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image30.png\" alt=\"An illustration of imbrication of clasts in a fluvial environment.\" width=\"597\" height=\"279\" \/><figcaption class=\"wp-caption-text\">Figure 6.4.5 An illustration of imbrication of clasts in a fluvial environment.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">Mud cracks form when a shallow body of water (e.g., a tidal flat or pond or even a puddle), into which muddy sediments have been deposited, dries up and cracks (<strong>Figure 6.4.6<\/strong>). This happens because the clay in the upper mud layer tends to shrink on drying, and so it cracks because it occupies less space when it is dry.<\/p>\n<figure style=\"width: 1135px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" src=\"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-content\/uploads\/sites\/187\/2024\/03\/image31.jpeg\" alt=\"Mudcracks in volcanic mud at a hot-spring area near Myvatn, Iceland.\" width=\"1135\" height=\"683\" \/><figcaption class=\"wp-caption-text\">Figure 6.4.6 Mudcracks in volcanic mud at a hot-spring area near Myvatn, Iceland.<\/figcaption><\/figure>\n<p class=\"import-NormalWeb\">The various structures described above are critical to understanding and interpreting the conditions that existed during the formation of sedimentary rocks. We\u2019ll be using this information to explain formations we see in U.S. National Parks today.<\/p>\n<p>&nbsp;<\/p>\n<h2><strong>Attributions:<\/strong><\/h2>\n<p>Modified from<em>: Physical Geology \u2013 2nd Edition by Steven Earle is used under a Creative Commons Attribution 4.0 International Licence.\u00a0 Download for free from the <\/em><a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/\"><em>B.C. Open Collection<\/em><\/a><em>.<\/em><\/p>\n<p>Modified from: Johnson, Chris , et al. <em>An Introduction to Geology<\/em>. Salt Lake Community College, 2017, opengeology.org\/textbook\/. (Licensed under a <a href=\"http:\/\/creativecommons.org\/licenses\/by-nc-sa\/4.0\/\">Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License<\/a>.)<\/p>\n<p>Figure 5.1.1 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p>Figure 5.1.2 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p>Figure 5.1.3 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p>Figure 5.1.4 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p>Figure 5.2.1 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p>Figure 5.2.2 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p>Figure 5.2.4 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-5-weathering-and-soil\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p>Figure 6.3.1 <a href=\"http:\/\/en.wikipedia.org\/wiki\/Depositional_environment#mediaviewer\/File:SedimentaryEnvironment.jpg\">Schematic diagram showing types of depositional environment<\/a> \u00a9 <a href=\"http:\/\/commons.wikimedia.org\/wiki\/User:Mikenorton\">Mike Norton<\/a>. Adapted by Steven Earle. CC BY-SA.<\/p>\n<p>Figure 13.3.1 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-13-streams-and-floods\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p>Figure 13.3.2 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-13-streams-and-floods\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p>Figure 13.3.4 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-13-streams-and-floods\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p class=\"import-Normal\">Figure 6.4.1 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p class=\"import-Normal\">Figure 6.4.2 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p class=\"import-Normal\">Figure 6.4.3 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p class=\"import-Normal\">Figure 6.4.4 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p class=\"import-Normal\">Figure 6.4.5 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p class=\"import-Normal\">Figure 6.4.6 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<p class=\"import-Normal\">Figure 6.4.7 by <a href=\"https:\/\/opentextbc.ca\/physicalgeology2ed\/part\/chapter-6-sediments-and-sedimentary-rocks\/\">Steven Earle<\/a>, <a href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/deed.en\">CC BY 4.0<\/a><\/p>\n<\/div>\n","protected":false},"author":101,"menu_order":2,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-135","chapter","type-chapter","status-publish","hentry"],"part":3,"_links":{"self":[{"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/pressbooks\/v2\/chapters\/135","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/wp\/v2\/users\/101"}],"version-history":[{"count":20,"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/pressbooks\/v2\/chapters\/135\/revisions"}],"predecessor-version":[{"id":420,"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/pressbooks\/v2\/chapters\/135\/revisions\/420"}],"part":[{"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/pressbooks\/v2\/parts\/3"}],"metadata":[{"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/pressbooks\/v2\/chapters\/135\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/wp\/v2\/media?parent=135"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/pressbooks\/v2\/chapter-type?post=135"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/wp\/v2\/contributor?post=135"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.ccconline.org\/ppscgey1108geologyofnationalparks\/wp-json\/wp\/v2\/license?post=135"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}