ORGAnic rocks
Organic rocks form when dead plants and animal remains are deposited into thick layers. It is common under the ocean, at the sea floor- but also occurs on land. Shells, and bones are two of the most common "ingredients" sometimes found in organic rocks. Limestone and coal are two wonderful examples of organic sedimentary rocks. Coal forms from swamp plant remains that eventually get buried deep in water. As the layer of plants build up, the heaviness of the layers of decaying plants squeezes- and over millions of years, the layers SLOWLY change to coal.