In chemistry, deposition is the settling of particles (atoms or molecules) or sediment from a solution, suspension mixture or vapor onto a pre-existing surface. Deposition generally results in growth of new phase and is of fundamental importance in a large number of scientific disciplines and practical applications, the most obvious ones being in material science, geology, meteorology and chemical engineering. The term is also widely used in earth science to describe the same process in a geological sense. Deposition of particles is an aggradational process — one that builds a landform — as opposed to a degradational process that erodes or reduces the size of a landform. For example, a river mouth delta is formed by deposition of sediment carried by the stream as the river current diminishes upon encountering the sea.
