In some parts of the world, windblown dust and silt blanket the land. This layer of fine, mineral-rich material is called loess.
Loess is mostly created by wind, but can also be formed by glaciers. When glaciers grind rocks to a fine powder, loess can form. Streams carry the powder to the end of the glacier. This sediment becomes loess.
Loess ranges in thickness from a few centimeters to more than 91 meters (300 feet). Unlike other soils, loess is pale and loosely packed. It crumbles easily; in fact, the word “loess” comes from the German word for “loose.” Loess is soft enough to carve, but strong enough to stand as sturdy walls. In parts of China, residents build cave-like dwellings in thick loess cliffs.
Extensive loess deposits are found in northern China, the Great Plains of North America, central Europe, and parts of Russia and Kazakhstan. The thickest loess deposits are near the Missouri River in the U.S. state of Iowa and along the Yellow River in China.
Loess accumulates, or builds up, at the edges of deserts. For example, as wind blows across the Gobi, a desert in Asia, it picks up and carries fine particles. These particles include sand crystals made of quartz or mica. It may also contain organic material, such as the dusty remains of skeletons from desert animals.
On the far side of the desert, moisture in the air causes the particles and dust to settle on the ground. There, grass and the roots of other plants trap the dust and hold it to the ground. More dust slowly accumulates, and loess is formed.
Loess often develops into extremely fertile agricultural soil. It is full of minerals and drains water very well. It is easily tilled, or broken up, for planting seeds. Loess usually erodes very slowly—Chinese farmers have been working the loess around the Yellow River for more than a thousand years.
Photograph by Phil Scherme
Yellow River
The Yellow River gets its name from the yellow loess suspended in the water.
to gather or collect.
to cover entirely.
chemical compound (CaCO3) found in most shells and many rocks.
type of mineral that is clear and, when viewed under a microscope, has a repeating pattern of atoms and molecules.
area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.
to wear away.
very large.
able to produce crops or sustain agriculture.
very thin.
type of plant with narrow leaves.
grassland region of North America, between the Rocky Mountains and the Mississippi River.
type of mineral that can be split into thin, see-through sheets.
inorganic material that has a characteristic chemical composition and specific crystal structure.
(4,382 kilometers/2,723 miles) river in the western United States.
wetness.
composed of living or once-living material.
nearly white or lacking in color.
small piece of material.
common type of mineral.
natural substance composed of solid mineral matter.
part of a plant that secures it in the soil, obtains water and nutrients, and often stores food made by leaves.
small, loose grains of disintegrated rocks.
bones of a body.
top layer of the Earth's surface where plants can grow.
body of flowing fluid.
rock, earth, and gravel left behind by a retreating or melting glacier.
movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.
(5,464 kilometers/3,395 miles) river in China. Also called the Huang River.
