Key Terms

a force of 100,000 Newtons acting on a surface area of 1 square meter; the average pressure of Earth’s atmosphere at sea level is 1.013 bars
igneous rock produced by the cooling of lava; makes up most of Earth’s oceanic crust and is found on other planets that have experienced extensive volcanic activity
movement caused within a gas or liquid by the tendency of hotter, and therefore less dense material, to rise and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat
the central part of the planet; consists of higher density material
the outer layer of a terrestrial planet
in geology, a crack or break in the crust of a planet along which slippage or movement can take place, accompanied by seismic activity
a type of igneous silicate rock that makes up most of Earth’s continental crust
greenhouse effect
the blanketing (absorption) of infrared radiation near the surface of a planet—for example, by CO2 in its atmosphere
greenhouse gas
a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range; on Earth, these atmospheric gases primarily include carbon dioxide, methane, and water vapor
igneous rock
rock produced by cooling from a molten state
the region around a planet in which its intrinsic magnetic field dominates the interplanetary field carried by the solar wind; hence, the region within which charged particles can be trapped by the planetary magnetic field
the largest part of Earth’s interior; lies between the crust and the core
mass extinction
the sudden disappearance in the fossil record of a large number of species of life, to be replaced by fossils of new species in subsequent layers; mass extinctions are indicators of catastrophic changes in the environment, such as might be produced by a large impact on Earth
metamorphic rock
rock produced by physical and chemical alteration (without melting) under high temperature and pressure
(O3) a heavy molecule of oxygen that contains three atoms rather than the more normal two
a complex sequence of chemical reactions through which some living things can use sunlight to manufacture products that store energy (such as carbohydrates), releasing oxygen as one by-product
plate tectonics
the motion of segments or plates of the outer layer of a planet over the underlying mantle
primitive rock
rock that has not experienced great heat or pressure and therefore remains representative of the original condensed materials from the solar nebula
rift zone
in geology, a place where the crust is being torn apart by internal forces generally associated with the injection of new material from the mantle and with the slow separation of tectonic plates
sedimentary rock
rock formed by the deposition and cementing of fine grains of material, such as pieces of igneous rock or the shells of living things
seismic wave
a vibration that travels through the interior of Earth or any other object; on Earth, these are generally caused by earthquakes
the layer of Earth’s atmosphere above the troposphere and below the ionosphere
the sideways and downward movement of the edge of a plate of Earth’s crust into the mantle beneath another plate
the lowest level of Earth’s atmosphere, where most weather takes place
a place where material from a planet’s mantle erupts on its surface
This book was adapted from the following: Fraknoi, A., Morrison, D., & Wolff, S. C. (2016). Key Terms. In Astronomy. OpenStax. under a Creative Commons Attribution License 4.0
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PPSC AST 1120: Stellar Astronomy by OpenStax is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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