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Deposition is the process by which wind or water sediment settles out in layers. Furthermore, over time, the remains of living things may harden in this sediment and change into fossils. After sediment is deposited the processes of compaction and cementation change the fragments into sedimentary rock. Compaction. At first, the fragments of rock lie loosely together. But gradually, over many, many years these thick layers build up. This build up becomes heavy and presses down on the layers beneath it. Compaction is the pressing down of layers forcing the sediments to fit closer together. Over millions of years, this process can squeeze fragments tightly together. The layers often remain visible in the rock and may be used to identify sedimentary rock. Cementation
Physical processes that break rock apart without changing its chemical makeup; can be caused by ice wedging, animals, and plant roots. Mechanical weathering. Mechanical weathering process that occurs when water freezes in the cracks of rocks and expands, causes the rock to break apart. Ice wedging. Occurs when chemical reactions dissolve the minerals in rocks or change them into different minerals.