Popular in Geol 113-2
Popular in Geology
This 5 page Class Notes was uploaded by Katie Thedford on Friday September 23, 2016. The Class Notes belongs to 20841 at Fort Lewis College taught by Allie Jackson in Fall 2016. Since its upload, it has received 4 views. For similar materials see Geol 113-2 in Geology at Fort Lewis College.
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Date Created: 09/23/16
Geology Surface Processes Weathering, soil, and mass wasting Mass wasting- The transfer of rock and soil downslope due to gravity. Erosion- The physical removal of material by mobile agents such as water, wind, and ice. Weathering- The physical breakdown or chemical alteration of rocks near or at earth’s surface. Transforms solid rock into sediment. Weathering types- o Physical (mechanical) Physical forces break down the rock Composition of rock does not change “disintegration” o Chemical Transformation of rock into new substances Jointing –pattern of fractures in the rock body Frost wedging/Thermal expansion Pressure unloading- “Yosemite” exfoliation Biological activity- root expansion or burrowing Glacial plucking and scouring Water and wind Sedimentary rocks o Rocks that have been eroded into smaller particles o The Rock Cycle Igneous->weathering->sedimentary Lithification- “becomes a rock” Sediment- the unconsolidated materials formed from the breakdown of rocks o Compaction- pressure bonds grains (overburden) o Cementation-material between grains holds them together o Precipitation- solid comes out of a solution o Porosity- % of void space between grains o Permeability- measure of how well a fluid can go through a sedimentary rock, arrangement of void spaces Sedimentary rocks Contain evidence of past environments Provide information about depositional environments Provides information about how sediment is transported 2 Types of Sedimentary rocks Clastic (detrital)-solidified masses of clasts Identified based on characteristics of clasts: Size Shape (sphericity) Sorting composition o Sedimentary environment of coarse conglomerates Alluvial fans-proximal Fluvial systems-braided streams o Sedimentary environment of fine conglomerates Alluvial fans-more distal Fluvial systems-rivers o Sedimentary environments of sandstones Alluvial fans-very distal Fluvial systems- desert dunes o Sedimentary environments of siltstones Alluvial fans-tidal flats Fluvial systems- floodplains o Sedimentary environments of shale Fluvial systems- floodplains 3 Biochemical sedimentary rocks- Named from substance they are made of and the fragment size Biochemical-minerals precipitated by living organisms that make up rock Organic- made of remnants of plants or algae (coal) Chemical- minerals precipitated out of solutions make up rock Calcite- Limestone (can be micrite, granular, fossiliferous, etc) Chalk (powderized calcite) Coquina (shell fragments) Microcrystalline- Chert 4 Organic Sedimentary Rocks Rich in carbon, so characteristically dark gray or black in color Can be almost pure carbon (coal) Can be mixed with other sediments (black shale) Chemical Sedimentary Rocks Precipitate out of solutions, so it depends on the chemistry of the solution Halite: rock salt Gypsum: Rock Gypsum Dolomite: Dolostone Calcite: calcareous Tufa 5
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