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1. Wind , water, ice, sunlight, and gravity all cause rock to physically weather into fragments. 2. Through the process of erosion, these rock and mineral fragments, called sediments, are moved from one place to another. 3. eventually , the sediment is deposited in layers. 4. As new layers of sediments are deposited, they cover the older layers. The older layers become compacted. 2. Organic sedimentary rock forms from the remains of once-living plants and animals. Some limestone is made of the skeletons of tiny organisms called coral. They are small but live in colonies called reefs. . 3. Chemical sedimentary rocks form when minerals crystallize out of a solution, such as sea water, to become a rock. They form from solutions of dissolved minerals and water. The skeletons of sea animals which are made of calcium carbonate, collect on the ocean floor. These animal remains eventually become cemented together to form fossiliferous limestone. Another type of sedimentary rock is coal. Coal forms underground when partially decomposed plant material is buried beneath sediment and is changed into coal by increasing heat and pressure. The most important feature of sedimentary rocks is stratification. Stratification is the process in which sedimentary rocks are arranged in layers. Strata differs from one another depending on the kind, size, and color of sediment. Sedimentary rocks sometimes record the motion of wind and water waves on lakes, oceans , rivers, and sand dunes in features called ripple marks. Structures called mud cracks form when fine grained sediments at the bottom of a shallow body of water are exposed to the air and dry out.