Sedimentary Rocks
How sedimentary rocks are formed A sedimentary rock is formed from pieces or sediments of rocks, plants, or animals. The sediments are cemented together, at or near the Earth’s surface.
What is the process in which sedimentary rocks form? Weathering Erosion Deposition Compaction Cementation
Weathering Weathering breaks rocks into pieces through wind, water, ice, sunlight, and gravity.
Erosion moves sediments from one place to another.
Deposition drops the sediment into layers.
Compaction presses the layers of sediment together.
Cementation glues the sediments together.
A rock is said to be “stratified” if it has strata, or layers.
Types of sedimentary rock
Organic sedimentary rock Forms from decayed plants and animals Usually formed in oceans or swamps
Examples of Organic sedimentary rocks Limestone (organic) Coal
Clastic Sedimentary Rock Clastic sedimentary rock is made of fragments of rocks cemented together by a mineral such as calcite or quartz. Classified according to the size of the fragments.
Example of clastic sedimentary rock: Conglomerate A rock composed of rounded fragments varying from small pebbles to large boulders in cement (such as hardened clay)
Example of clastic sedimentary rock: Breccia Breccia is a rock composed of sharp fragments embedded in a fine-grained matrix (such as sand or clay)
Chemical Sedimentary rock Chemical sedimentary rock forms from solutions of dissolved minerals and water. The material crystallizes and forms the minerals that make up the rock.
Examples of Chemical sedimentary rock Dolomite Limestone (chemical)