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weathering and sedimentary rocks

Earth's external processes. Weathering

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weathering and sedimentary rocks

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    1. Weathering and Sedimentary Rocks

    2. Earths external processes

    3. Weathering Two types Mechanical weathering breaking of rocks into smaller pieces Types of mechanical weathering Frost wedging Unloading Thermal expansion Biological activity

    4. Frost wedging

    5. Weathering Chemical weathering Breaks down rock components and internal structures of minerals Most important agent is water Responsible for transport of ions and molecules involved in chemical processes

    7. What is a sedimentary rock? Sedimentary rocks are products of mechanical and chemical weathering They account for about 5% (by volume) of Earths outer 10 miles Contain evidence of past environments Provide information about sediment transport Often contain fossils

    8. 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

    9. Turning sediment into rock Many changes occur to sediment after it is deposited Diagenesis = chemical, physical, and biological changes that take place after sediments are deposited Occurs within the upper few kilometers of Earths crust

    10. What is a sedimentary rock? Sedimentary rocks are products of mechanical and chemical weathering They account for about 5% (by volume) of Earths outer 10 miles Contain evidence of past environments Provide information about sediment transport Often contain fossils

    11. 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

    12. Turning sediment into rock Many changes occur to sediment after it is deposited Diagenesis = chemical, physical, and biological changes that take place after sediments are deposited Occurs within the upper few kilometers of Earths crust

    13. Turning sediment into rock Diagenesis Includes Recrystallization development of more stable minerals from less stable ones Lithification sediments are transformed into solid rock by Compaction and cementation Natural cements include calcite, silica, and iron oxide

    14. 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

    15. Detrital sedimentary rocks The chief constituents of detrital rocks include Clay minerals Quartz Feldspars Micas Particle size is used to distinguish among the various rock types

    17. Detrital sedimentary rocks Common detrital sedimentary rocks Shale Mud-sized particles in thin layers that are commonly referred to as laminea Most common sedimentary rock Sandstone Composed of sand-sized particles Forms in a variety of environments Quartz is the predominant mineral

    18. Shale with plant remains

    19. Quartz sandstone

    20. Detrital sedimentary rocks Conglomerate and breccia Both are composed of particles greater than 2mm in diameter Conglomerate consists largely of rounded gravels Breccia is composed mainly of large angular particles

    21. Conglomerate

    22. Breccia

    23. Chemical sedimentary rocks Consist of precipitated material that was once in solution Precipitation of material occurs by Inorganic processes Organic processes (biochemical origin)?

    24. Chemical sedimentary rocks Common chemical sedimentary rocks Limestone Most abundant chemical rock Composed chiefly of the mineral calcite Marine biochemical limestones form as coral reefs, coquina (broken shells), and chalk (microscopic organisms)? Inorganic limestones include travertine and oolitic limestone

    25. Coquina

    26. Fossiliferous limestone

    27. Chemical sedimentary rocks Common chemical sedimentary rocks Evaporites Evaporation triggers deposition of chemical precipitates Examples include rock salt and rock gypsum

    28. Classification of sedimentary rocks Sedimentary rocks are classified according to the type of material Two major groups Detrital Chemical

    29. Classification ofsedimentary rocks Two major textures are used in the classification of sedimentary rocks Clastic Discrete fragments and particles All detrital rocks have a clastic texture Nonclastic Pattern of interlocking crystals May resemble an igneous rock

    30. Identification of sedimentary rocks

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