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Chapter 15: Weathering and Mass Movement, 15.3 VOCAB, 15.1 VOCAB, 15.2…
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15.3 VOCAB
mass movement - downslope movement of rock, soil, snow, or ice caused by gravity.
soil creep - the imperceptible downslope movement of soil and regolith as their volume changes in seasonal expansion-contraction cycles.
solifluction - a type of soil creep in which freeze-thaw cycles cause the soil to flow slowly downslope in overlapping sheets.
slump - a type of mass movement in which regolith detaches and slides downslope along a spoon-shaped failure surface and comes to rest more or less as a unit.
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debris flow - a fast-flowing slurry of mud mixed with large objects, such as rocks and vegetation.
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debris slide - a landslide that consists of a mixture of rocks, soil, and vegetation.
avalanche - a turbulent cloud of rock debris or snow that is mixed with air and races quickly down a steep slope.
rockfall - a type of mass movement in which rocks tumble off a vertical or nearly vertical cliff face.
talus - pieces of angular broken rock that accumulate at the base of a steep slope or vertical cliff.
15.1 VOCAB
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erosion - the transport of rock fragments by moving water, ice, or air.
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physical weathering - the breakdown of rocks into smaller pieces without altering the chemical makeup of the rock.
exfoliation - a physical weathering process in which joints form parallel to a rock surface, creating sheetlike slabs of rock.
frost wedging - a physical weathering process in which water trapped in an opening in a rock freezes and expands, causing the opening to grow.
salt wedging - a physical weathering process in which salt crystals grow in pore spaces on a rock's surface and dislodge individual mineral grains within the rock.
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chemical weathering - a process that changes the minerals in a rock through chemical reactions involving water.
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15.2 VOCAB
karst - an area dominated by the weathering of carbonate rocks, usually limestone.
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1.) Physical Weathering
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pressure-release jointing occurs when overlying rocks and sediments (overburden) are removed from rocks that formed at great depths.
after overburden is removed, the enormous pressure associated with deep burial lessens, and the rock expands slightly, creating joints.
exfoliation creates sheetlike slabs of rock. these slabs of rock peel off and create broken horizontal slabs of rock that can slip off the rock face.
frost wedging will cause on opening to grow. in it's frozen state, water increases its mass by 10%. repeated freezing and thawing of rock joints pries the rocks apart over time.
salt wedging weakens rocks so that wind and rain can further disintegrate it. salt crystal growth requires that the rock surface be continually wetted, then dried.
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2.) Chemical Weathering
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hydration causes rock or mineral to expand and weaken. it changes the texture, composition, and volume of minerals in rocks.
in oxidation, oxygen atoms combine with the minerals in rocks and weaken them.
biochemical weathering refers to the chemical weathering resulting from the activities of living organisms.
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15.1 Weathering Rocks
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tectonic forces act sporadically across Earth's surface, but the forces that reduce vertical relief are present nearly everywhere on land and never rest.
eventually, all rocks exposed at Earth's surface will weather, either physically or chemically.
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1.) Karst Processes
through carbonation, acidic water reacts with the calcite in limestone. this causes the minerals to dissolve in water and be carried away (dissolution).
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2.) Assessing the Risk
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the TRMM (Tropical Rainfall Measuring Mission) evaluates landslide risk by using satellites to measure rainfall amounts and rainfall intensity for all tropical areas. these data are used in conjunction with the mass movement risk map to provide real-time warnings.
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