04_weathr_sed_09_post

04_weathr_sed_09_post - cture 4: cture 4: 1 Sedimentary...

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Unformatted text preview: cture 4: cture 4: 1 Sedimentary rock : rock that formed at or near the Earth’s surface by precipitation of minerals from water solutions, by growth of skeletal material in organisms, or by cementing together of shell fragments or loose small pieces (grains) derived from preexisting rocks. Sediment : loose (unconsolidated) fragments. 4: Weathering & Sedimentary Rocks Sedimentary layers in Grand Canyon. Sedimentary layers in Grand Canyon. Photo: P.L. Kresan Photo: P.L. Kresan Weathering of granite produces sediment. Photo: S. Marshak. cture 4: cture 4: 2 Why this is important • • Weathering is the first step in the process of wearing Weathering is the first step in the process of wearing down what tectonics builds up. down what tectonics builds up. Photo: P.L. Kresan Photo: P.L. Kresan cture 4: cture 4: 3 Why this is important • • Weathering produces soils and concentrates certain mineral resources. Weathering produces soils and concentrates certain mineral resources. Photo: L. Lefever • Sedimentary rocks contain fossil fuels & many non-metallic mineral resources. Photo: Chevron Corp. cture 4: cture 4: 4 Why this is important • Sedimentary rocks are the prime recorders of geologic history. Photo: P.L. Kresan Photo: P.L. Kresan • Only rock type that contains fossils, the record of the history of life. Photo: P.L. Kresan Photo: P.L. Kresan cture 4: cture 4: 5 Origin of sediment Fig. 7.16 Fig. 7.16 • Weathering : mechanical disintegration and chemical decomposition of rock to produce sediment. • Erosion : removal of (generally weathered) rock or rock by-products. • Transportation : movement of weathered material by moving air, water, ice. • Deposition : accumulation of previously transported sediment. cture 4: cture 4: 6 Two types of weathering • Mechanical (physical) weathering : reduces the size of rock and mineral fragments without changing their composition • Chemical weathering : results in a change in chemical composition. cture 4: cture 4: 7 Mechanical weathering • • Frost wedging : water in cracks expands by 9% when it freezes Fig. 7.6a Fig. 7.6a Taylor Valley, Victoria Land, Antarctica. Photo: M. Hambrey Analogy: freezing water bursts Analogy: freezing water bursts pipes and breaks water bottles pipes and breaks water bottles placed in freezer. placed in freezer. cture 4: cture 4: 8 Mechanical weathering • Root wedging & burrowing: mechanical weathering produced by plants and animals See Fig....
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This note was uploaded on 11/17/2011 for the course SCIENCE 460:100 taught by Professor Staff during the Spring '10 term at Rutgers.

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04_weathr_sed_09_post - cture 4: cture 4: 1 Sedimentary...

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