Sedimentary Rock Sedimentary Rock Sedimentary rock is created

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 �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