Deposition is the process that follows erosion. Erosion is the removal of particles (rock, sediment etc.) from a landscape, usually due to rain or wind. Deposition begins when erosion stops; the moving particles fall out of the water or wind and settle on a new surface. This is deposition.
The overall cause for deposition is erosion, since the particles need to be moving in order to stop. However, there has to be something that causes the erosion to stop and the deposition to begin. This transition is caused by a change in the agent of transport. Water can slow or evaporate, allowing sediment to stop being carried along. Wind can die down and release soil. Ice can melt and release its hold. Any such change begins the process of deposition.
Erosion can be a very destructive force, but together with deposition, it can also be a force of creation. These two processes are responsible for the creation of new landscapes, including hills, valleys and coastlines. Though erosion can alter an area, the affected parts are not destroyed but simply moved. Deposition allows these parts to settle elsewhere.
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Various changes in the surrounding environment can aid in the process of deposition. Trees and plants can slow the flow of water or divert the force of wind, which can allow the process to begin. Similarly, hills, buildings, large rocks and other obstacles can halt or slow a flowing agent enough for sediment to fall out and settle.
Give and Take
Though deposition means the end of erosion, it does not necessarily mean that the newly settled particles are now safe. Erosion and deposition are continuous processes. Though the particles have resettled, they are likely to be picked up another day and moved somewhere else. This give-and-take process helps the environment maintain equilibrium.