Chapter 20 HW – Flashcards
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What is the most abundant element for Earth as a whole?
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Iron
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What is the most abundant element in Earth's crust?
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oxygen
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What is the second most abundant element?
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silicon
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What is the most abundant mineral in Earth's crust?
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feldspar
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What is the second most abundant mineral?
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quartz
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As minerals crystallize in cooling magma, which minerals are the first to crystallize: the minerals with lower amounts of silica or the minerals with higher amounts of silica?
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the minerals with lower amounts of silica
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In Earth's interior, does temperature increase or decrease with depth?
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Increases.
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What lies underneath volcanic features at Earth's surface?
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magma chambers and volcanic conduits
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What is the difference between a dike and a sill?
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A dike intrudes across sedimentary layers, and a sill intrudes between sedimentary layers.
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What is a volcanic conduit called after the conduit has solidified and been exposed by erosion?
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volcanic neck
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Why are volcanic rocks often exposed at Earth's surface as hills, ridges, and mountains surrounded by areas of lower elevation?
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Volcanic rocks are often more resistant to erosion than surrounding rock.
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What is a magma chamber called after the conduit has solidified and been exposed by erosion?
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batholith
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When will magma rise to Earth's surface?
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when the magma is less dense than adjacent rock
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In general, when will melted rock in the mantle rise?
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almost always
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How are felsic magmas formed?
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Heat from the mantle melts part of the lower crust.
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How do mafic volcanic rocks get to Earth's surface?
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Pressure from overlying crust forces mantle magmas through cracks to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock.
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In general, why does Earth's crust sit on top of the mantle?
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Earth's crust is less dense than the mantle.
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Why does water frozen in the cracks of a rock help to break down the rock?
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Water expands when frozen and physically forces the rock apart.
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What is salt weathering?
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the formation of minerals in rock cracks during the evaporation of salty water, forcing rock apart
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What do freeze-thaw and salt weathering have in common?
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Both freeze-thaw and salt weathering require rain and force rocks apart physically.
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Where do most metamorphic rocks form?
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between a few and many kilometers beneath Earth's surface
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How do metamorphic rocks reach Earth's surface?
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through removal of overlying rocks
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Could metamorphic rocks reach the surface of a planet without rock-uplifting processes?
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No, metamorphic rocks must be uplifted and exposed by erosion.
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How are metamorphic rocks formed?
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Preexisting rock is altered through heat and pressure.
