L08_Sedimentary_Rocks_Chemical_Weathering

Diamond a tough mineral is dicult to smash quartz jade

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Unformatted text preview: ocks are classified largely according to composi<on First step in produc<on of sediments is produc<on of topography by plate tectonics Sec<on of polymict conglomerate from offshore rock core, Alaska, approximate depth 10,000 n. Wikipedia conglomera<c rock, coastal California Table Mountain, Cape Province, South Africa Wikipedia Sandstone rocks from the Western US. These were originally deposited as sand dunes. thin sec<on photomicrograph showing rounded quartz sand grains Canyonlands N.P., Utah The rock layers are primarily sandstone shales, originally deposited as silts and clays in the western interior seaway, N. America, during the Late Cretaceous period (100 million years ago). limestone shale Clas<c sedimentary rocks: Rocks composed mainly of bits and pieces of eroded rocks shales, originally deposited as silts and clays in the western interior seaway, N. America, during the Late Cretaceous period (100 million years ago). Clas<c sedimentary rocks: Rocks composed mainly of bits and pieces of eroded rocks Maple Canyon, Utah physical weathering: the process of mechanical break- down of rocks and minerals. Grind, shader, smash, abrade, and wear are all good verbs pertaining to physical weathering. the suscep<bility of a mineral to physical weathering depends on it’s hardness and toughness a way to think about ‘hardness’ versus ‘toughness’: a hard mineral is difficult to scratch. diamond. a tough mineral is difficult to smash. quartz, jade. why is physical weathering relevant to climate and biogeochemistry? surface area. chemical weathering is limited by surface area. consider again the chemical weathering of K- feldspar to produce kaolinite clay: 2KAlSi3O8 + 2CO2 + 11H2O à༎ Al2Si2O5(OH)4 + 2K+ +2HCO3- + 4H4SiO4 KAlSi3O8 H2O CO2 the reac<on can only happen at the surface the...
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