loesses

Loess is a wind-blown sediment composed mainly of silt-sized particles, typically 2 to 50 micrometers in diameter. It forms extensive, relatively uniform blankets in temperate regions and is usually light in color, ranging from pale yellow to gray. Loess deposits are generally highly porous and can range from loosely consolidated to semi-cohesive, with thick, well layered sequences in places.

Formation and distribution: Loess accumulates during cold, dry phases of the climate when strong winds transport silt from glacial outwash plains and desert margins over long distances. Repeated deposition over many cycles has built up substantial thicknesses, sometimes hundreds of meters, in favorable locations. Today, major loess regions are found on every continent except Antarctica, with prominent examples including the Chinese Loess Plateau, the Central North American Loess Belt (from Nebraska to Illinois and into the Mississippi Valley), and extensive belts in eastern Europe and western Asia.

Soils and significance: The weathered product of loess is among the world's most fertile soils, especially where loess-derived soils host rich humus develop­ment and black-earth Chernozem-type profiles. These soils support intensive agriculture in regions such as northern China and parts of Europe and North America. However, loess is highly susceptible to erosion when vegetation is removed, making landscapes prone to gullying, landslides, and dust storms, as exemplified by historical dust events in the Great Plains and other arid-to-semiarid regions. Loess deposits also preserve detailed paleoenvironmental records, aiding reconstruction of past climatic changes.