Silt

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Silt deposits around house and car in New Orleans left by flooding from a breach in the London Avenue Canal

Silt is soil or rock that developed from granular material of a specific grain size.

Silty soil has much smaller particles than sandy soil so it’s smooth to the touch. When moistened, it’s soapy slick. When you roll it between your fingers, dirt is left on your skin.

Silty soil retains water longer, but it can’t hold on to as much nutrients as you’d want it to though it’s fairly fertile. Due to its moisture-retentive quality, silty soil is cold and drains poorly.

Grain size criteria[change | change source]

Silt particles range between a 1256 and 116 mm (3.9 to 62.5 μm), larger than clay but smaller than a sand. Silt is chemically distinct from clay, and unlike clay, grains of silt are about the same size in all dimensions.

Silt may occur as a soil or alternatively as suspended sediment in a water column of any surface water body. It may also exist as deposition soil at the bottom of a water body and it can occur as a deposit or as material transported by a stream or by a current in the ocean. Silt is easily transported in water and is fine enough to be carried long distances by air as 'dust'. Thick deposits of silty material that result from wind deposition are often called loess (a German term) or limon (French). Silt and clay contribute to turbidity in water.