loess (lĕs, lōˈəs, Ger. lös) [key], unstratified soil deposit of
varying thickness, usually yellowish and composed of fine-
grained angular mineral particles mixed with clay. It is found
in many regions of the world and is probably related to the
chernozem soils of Russia; extensive deposits occur along the
Mississippi River and its tributaries, on the Columbia Plateau
in Oregon, Washington, and Idaho, and in China. Loess is an
erosional product carried by the wind from adjacent deserts,
from frost-pulverized outwash of glaciers (during the
Pleistocene epoch), or from the floodplains of glacier-fed
streams. Studies of particles transported by wind from plains
recently denuded by tillage show that the material is sorted to
about the same degree as loess. Much of the loess in the United
States and Europe are of glacial origin; in China, of desert
origin and may reach up to 300 feet (90 meters) thick. Loess is
usually deep, fertile soil, rich in organic remains (especially
the shells of snails) and characterized