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31 Cards in this Set
- Front
- Back
weathering
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rocks disintegrate because they are exposed to earth's surface
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2 types of weathering
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physical and chemical
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physical weathering
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break rock into smaller and smaller fragments
falling rocks chipping off others, abrasion by sand, water freezing in fractures, plant roots causing cracks |
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chemical weathering
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dissolving rocks or some of the minerals in rocks
causes the remaining pieces to come apart in pieces |
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transportation
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debris from weathered rocks is moved
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main form of transportation
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water
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high energy streams move _____
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large boulders
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slow moving streams carry ______
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small debris
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sediment
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material moved by water
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some forms of transportation
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water, wind, glaciers
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deposition
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when the thing that is moving the sediment loses energy, the sediment gets deposited somewhere
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compaction
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reduction in pore (open) space between grains in sediment
sediment can get really thick so the pressure causes compaction of sediment grains |
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lithification
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sediment converted into rocks
deep burial, elevated temperature and pressure, presence of water new minerals might grow |
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2 groups of sedimentary rocks
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clastic (detrital) and chemical/biochemical
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clastic (detrital) sedimentary rocks
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composed of fragments (clasts) or pre-existing rocks
classified based on size of clasts |
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chemical and biochemical sedimentary rocks
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chemical elements that have been acquired mainly as a result of chemical weathering
some of these dissolved minerals can be precipitated directly from water |
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6 types of sedimentary rocks, by grain size (big to small)
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conglomerate, breccia, sandstone, siltstone, shale, mudstome
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size of clasts reflects ______
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energy of transporting agent
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clasts tend to be more _____ and less ______ when transported farther from source
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more round, less angular
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5 common structures in sedimentary rocks
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1) Bedding
2) cross bedding 3) graded bedding 4) ripple marks 5) mud cracks |
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Bedding
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stratification (layering)
most prominent structure represents surfaces on which deposition occurred horizontal |
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cross bedding
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sloping depositional surfaces
like surface of dunes and delta fronts |
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graded bedding
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stratification in a bed of sedimentary rocks
coarsest clasts occur at bottom clast size decreases toward top of bed |
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what is graded bedding a result of
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different settling velocities for different size clasts (larger and heavier clasts settle out first(
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each graded bed represents
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a single and sudden depositional event
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ripple marks
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small dune-like features
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ripple marks generally form in
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shallow waters
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size of ripple marks are related to
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velocities of current that form them
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shapes of ripple marks are related to
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current direction
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mud cracks
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form when deposits of mud dry out
as it dries, it shrinks and polygonal desiccation cracks form next layer of fine sediment will fill in and cover cracks, preserving them |
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where do mud cracks form
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areas that experience frequent wetting by shallow water and drying
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