Loess (/ˈloʊ.əs/, /ˈlʌs/, /ˈlɛs/, or /ˈlɜrs/) is a clastic predominantly silt-sized sediment, which is formed by the accumulation of wind-blown dust.
Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometre size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate. It is usually homogeneous and highly porous and is traversed by vertical capillaries that permit the sediment to fracture and form vertical bluffs.
The word loess, with connotations of origin by wind-deposited accumulation, is of German origin and means “loose.” It was first applied to Rhine River valley loess about 1821.
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