§ Sediment: means small pieces of rock
§ Formed by weathering, erosion and deposition.
o Weathering: the breaking down of rocks and other materials on earth’s surface (caused by wind and water)
o Erosion: The moving of materials caused by weathering
o Deposition: The process where sediments that were carried by erosion are put in a new location. (Usually involves compacting and cementing of many materials together)
§ Sedimentary rocks are classified by the composition of the materials in them.
§ There are three main categories:
o Clastic Rocks: made from fragments of existing rocks and the size and shape of those pieces. They are cemented together with clay, mud or sand.
§ Sandstone: made from sand-sized pieces
§ Shale: dust sized fragments (with mud or clay)
§ If over of the rock is made of pebbles, the rock is a conglomerate. Puddingstone is an example of a conglomerate.
o Organic Rocks: made from organisms that were once living.
§ Organic means living
§ Many were formed from shells of crustaceans and microorganisms.
§ Limestone, and coral reefs are examples
§ Chalk is a type of fine-grained limestone.
§ Coal is another example
o Chemical Rocks: formed when seas dried up, leaving minerals dissolve in the water.
§ Some Limestone forms this way.
§ Rock salt and Gypsum are other examples.