How do clastic sedimentary rocks differ from organic and chemical sedimentary rocks?
Clastic sedimentary rocks are caused by the erosion of inorganic materials, organic and chemical sedimentary rocks occur from the deposits of mainly organic materials
Erosion breaks down rocks, sedimentary layers, metaphoric rocks and igneous protrusions are all broken down by erosion. The pieces or clastic material is then deposited or redeposited in new sedimentary layers. These new layers are cemented, compacted, and chemically changed into sedimentary rocks.
Examples of clastic sedimentary rocks are conglomerates, sandstone, and shale. The size of the clastic material determines the type of sedimentary rock that is formed.
Organic sedimentary layers may not be caused by erosion at all. Coal which is an example of a sedimentary material is formed when organic material like plants are buried between other sedimentary layers. The organic material is then changed into coal an organic sedimentary layer by heat and pressure.
Chemical layers like limestone form when the organic material of sea shells precipitates out of solution to the bottom of a body of water. The precipitates accumulate at the body of the body of water forming the thick layers of limestone found on the continents.
Clastic sedimentary layers are formed by erosion and the accumulation of small broken bits of rock. Chemical sedimentary layers and organic sedimentary layers are not the result of erosion. Chemical sedimentary layers are the accumulation of precipitates of organic material. Organic sediments are the remains of buried plants and other living things.