An alluvial deposit is a geological term for small, eroded debris or material that has been transferred, often by water, and redistributed to another area. The alluvial material can range from small rocks to fine silt and sediment. The material then resettles into sedimentary deposits called alluvial deposits. Alluvial deposits can be useful to humans in a couple of ways. First, they can contain precious metal or gemstone deposits that have been exposed and transferred during the erosion process. Prospectors then search through this relatively soft rock much easier than hardened bedrock. Another way is with alluvial plains. Eroded material from higher elevations upstream in a river can deposit downstream as fine sediment and form very flat, level plains. The soil deposited can be fertile and ideal for growing crops. The Mississippi River alluvial plain in Arkansas, Mississippi, and Louisiana is an ideal example.