Silt

For other uses, see Silt (disambiguation).

Silt is soil or rock that develops from granular material between the size of sand and clay.

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

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

Silty soil holds water longer, but it can’t hold on to many nutrients, though it’s fairly fertile. Due to its moisture-capturing quality, silty soil is cold and drains poorly.

Grain size criteria

Silt particles range between a 1⁄256 and 1⁄16 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 after it is eroded elsewhere and transported by a stream or by a current. 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 more particles in the water.