Cementation is the process of cementing minerals coating the sediment grains and gluing them together into a fused rock. Digenesis is an accompanying process to lithification and is a low-temperature form of rock metamorphism. Finally, lithification is the process by which clay, sand, and other sediments on the bottom of the ocean or other bodies of water are slowly compacted into rocks from the weight of overlying sediments. Erosion is the movement of sediment by wind, water, or ice. Deposition is the process by which wind, water, or ice drops sediment in a new location which builds up the Earth's surface. The changes to the Earth's surface are slow changes that occur over a very long period of time.