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Sedimentary Rock. Sedimentary Rock. Sedimentary rock is created when existing rock breaks down into sediments , and then the sediments are recombined by compaction and cementation. Sedimentary Rock. Sediments are created by three forces: Weathering Erosion Deposition. Weathering.
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Sedimentary Rock • Sedimentary rock is created when existing rock breaks down into sediments, and then the sediments are recombined by compaction and cementation
Sedimentary Rock • Sediments are created by three forces: • Weathering • Erosion • Deposition
Weathering • Weathering is any process that breaks down rock. • There are two types of weathering • Chemical weathering • Mechanical weathering
Chemical Weathering • Chemical Weathering is the transformation of rock into one or more new compounds • Water is the most important agent of chemical weathering
Mechanical Weathering • Mechanical weathering occurs when physical forces break rock into smaller and smaller pieces without changing its composition
Mechanical Weathering • Three forces account for the majority of mechanical weathering: • Frost wedging • Unloading • Biological Activity
Frost Wedging • When liquids freeze they expand, causing rock to break apart.
Unloading • Unloading occurs when pressure is removed from a rock body causing it to expand and break
Biological Activity • The activities of plants and animals can cause rock to break apart • For example tree roots can break through rock layers, or borrowing animals creating holes in rock.
Erosion • Erosion is the removal of rock and its movement by water, wind, ice, or gravity.
Deposition • When water, wind, ice or gravity loses energy the sediments are released and deposited in a new area. • Sediments are deposited according to size, with larger sediments being released first
Sedimentary Rock • Compaction and cementation are the two processes that change sediment into sedimentary rock.
Compaction • Compaction is a process that squeezes, or compacts sediments
Cementation • Cementation takes place when dissolved minerals are deposited in tiny spaces among the sediments. • These minerals hold the sedimentary rocks together
Classification of Sedimentary Rock • Sedimentary rocks like igneous rock can be classified into two groups based on how the form: • Clastic Sedimentary Rock • Chemical Sedimentary Rock
Clastic Sedimentary Rock • Clastic Sedimentary Rocks are created when weathered bits of rocks or minerals are cemented together
Chemical and Biochemical Sedimentary Rocks • Chemical Sedimentary rocks are created when dissolved minerals precipitate from water solutions • Biochemical Sedimentary rocks are created when living or once living materials are cemented together
Features of Sedimentary Rock • Sedimentary rock can have unique features that can help us interpret the history of the Earth. • Some Features include: • Ripples • Mud Cracks • Fossils