lo·ess / les; ləs; ˈlōˌes/ • n. Geol. a loosely compacted yellowish-gray deposit of windblown sediment of which extensive deposits occur, e.g., in eastern China and the American Midwest.DERIVATIVES: lo·ess·i·al / ˈlesēəl; ˈlə-; lōˈes-/ adj.lo·ess·ic / ˈlesik; ˈlə-; lōˈes-/ adj.

loess Unconsolidated, wind-deposited sediment composed largely of silt-sized quartz particles (0.015–0.05 mm diameter) and showing little or no stratification. It occurs widely in the central USA, northern Europe, Russia, China, and Argentina. It can give rise to a rugged topography with steep slopes (up to 70°).

loess Unconsolidated, wind-deposited sediment composed largely of silt-sized quartz particles (0.015–0.05 mm diameter) and showing little or no stratification. It occurs widely in the central USA, northern Europe, Russia, China, and Argentina. It can give rise to a rugged topography with steep slopes (up to 70°). The soils derived from loess are of a very high quality and support excellent crop yields.

loess Unconsolidated, wind-deposited sediment composed largely of silt-sized quartz particles (0.015–0.05 mm diameter) and showing little or no stratification. It occurs widely in the central USA, northern Europe, Russia, China, and Argentina. It can give rise to a rugged topography with steep slopes (up to 70°). The soils derived from loess are of a very high quality and support excellent crop yields.

loess Fine-grained clay, a sedimentary material made up of rock fragments. It is earthy, porous and crumbly, and usually yellowish or brown in colour. Loess consists of mainly quartz and calcite from glaciated areas, blown by the wind and often built up into thick layers. The largest expanse is in the Huang He valley, n China.