A horizon (zone of leaching) | The top layer of soil, characterized by the downward movement of water; also called zone of leaching.
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B horizon (zone of accumulation) | A soil layer characterized by the accumulation of material leached downward from the A horizon above; also called zone of accumulation.
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chemical weathering | The decomposition of rock resulting from exposure to water and atmospheric gases.
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C horizon | A soil layer composed of incompletely weathered parent material.
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clay mineral | A hydrous aluminum-silicate that occurs as a platy grain of microscopic size with a sheet silicate structure.
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differential weathering | Varying rates of weathering resulting from some rocks in an area being more resistant to weathering than others.
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erosion | The physical removal of rock by an agent such as running water, glacial ice, or wind.
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exfoliation | The stripping of concentric rock slabs from the outer surface of a rock mass.
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exfoliation dome | A large, rounded landform developed in a massive rock, such as granite, by the process of exfoliation.
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frost action | Mechanical weathering of rock by freezing water.
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frost heaving | The lifting of rock or soil by the expansion of freezing water.
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frost wedging | A type of frost action in which the expansion of freezing water pries a rock apart.
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hematite | A type of iron oxide that has a brick-red color when powdered; Fe2O3.
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laterite | Highly leached soil that forms in regions of tropical climate with high temperatures and very abundant rainfall.
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limonite | A type of iron oxide that is yellowish-brown when powdered; Fe2O3·nH2O.
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loam | Soil containing approximately equal amounts of sand, silt, and clay.
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mechanical weathering | The physical disintegration of rock into smaller pieces.
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O horizon | Dark-colored soil layer that is rich in organic material and forms just below surface vegetation.
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pressure release | A significant type of mechanical weathering that causes rocks to crack when overburden is removed.
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residual soil | Soil that develops directly from weathering of the rock below.
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sheet joints | Cracks that develop parallel to the outer surface of a large mass of expanding rock, as pressure is released during unloading.
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soil | A layer of weathered, unconsolidated material on top of bedrock; often also defined as containing organic matter and being capable of supporting plant growth.
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soil horizon | Any of the layers of soil that are distinguishable by characteristic physical or chemical properties.
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spheroidally weathered boulder | Rounded by weathering from an initial blocky shape.
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transportation | The movement of eroded particles by agents such as rivers, waves, glaciers, or wind.
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transported soil | Soil not formed from the local rock but from parent material brought in from some other region and deposited, usually by running water, wind, or glacial ice.
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weathering | The group of processes that change rock at or near Earth’s surface.
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E horizon | soil zone where downward movement of water removes fine-grained soil components such as clay.
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