- Slides: 20
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 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