Essentials of Geology (10th Edition)

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Sediments and Sedimentary Rocks Sediments and Sedimentary Rocks Grand Canyon, AZ Grand Canyon, AZ Sedimentary Rocks
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What is a sedimentary rock?  Sedimentary rocks are products of  mechanical and chemical weathering They account for about 5 percent (by  volume) of Earth’s outer 10 miles They contain evidence of past  environ-ments Provide information about sediment  transport Often contain fossils
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What is a sedimentary rock?  Sedimentary rocks are important for  economic considerations because they  may contain Coal Petroleum and natural gas Sources of iron, aluminum, and  manganese
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Why are Why are sedimentary rocks sedimentary rocks important? important? An average American consumes 12+ tons 12+ tons each year each year of metallic metallic and nonmetallic and nonmetallic resources resources, plus another 12 tons each 12 tons each year year of energy energy resources resources, almost all coming from sedimentary sources.
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Most energy resources are sedimentary Drilling for gas in OK offshore oil rig in CA coal
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Sedimentary rocks preserve a record of past life on Earth via fossils 350 Ma plant fossils 400 Ma trilobite fossil 350 Ma plant fossils 400 Ma trilobite fossil
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Sediments Sediments are unconsolidated particles of rock and mineral created by weathering and erosion Sedimentary Sedimentary rock rock is produced by the lithification of sediment, typically by compaction and introduction of a cement Roughly 75% of rock outcrops on land are sedimentary, but only 5% of the upper 10 miles of crust is sedimentary.
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Weathering of some “parent rock” Weathering of some “parent rock” produces produces sediment sediment erosion and erosion and transport to a place of deposition transport to a place of deposition compaction and cementation compaction and cementation sedimentary rock sedimentary rock This area is sediment derived from older This area is sediment derived from older sedimentary rocks forming the cliffs. sedimentary rocks forming the cliffs.
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    Turning sediment into rock Many changes occur to sediment after  it is deposited Diagenesis  – all of the chemical,  physical, and biological changes that  take place after sediments are  deposited Occurs within the upper few kilometers  of Earth’s crust
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Turning sediment into rock Diagenesis Includes Recrystallization  – development of more  stable minerals from less stable ones Lithification  – unconsolidated sediments  are transformed into solid sedimentary rock  by » Compaction  » Cementation  by calcite, silica, and iron  oxide
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Types of sedimentary rocks   Sediment originates from mechanical  and/or chemical weathering Rock types are based on the source of  the material Detrital rocks  – transported sediment as  solid particles Chemical rocks  – sediment that was  once in solution
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Ch06 - Sediments and Sedimentary Rocks Sediments Grand...

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