Dust storms may form in desert areas when
strong winds that blow across desert regions pick up dust
made of silt and clay particles and transport them thousands
of kilometers from their source. For instance, dust from China
is found in Hawaii, and the Sahara commonly drops dust in
Europe. This dust is a nuisance, has a significant influence on
global climate, and has at times (as in the dust bowl days of
the 1930s) been known to nearly block out the Sun.
Loess is a name for silt and clay deposited by wind. It
forms a uniform blanket that covers hills and valleys at many
altitudes, which distinguishes it from deposits of streams. In
Shaanxi Province, China, an earthquake that killed 830,000
people in 1556 had such a high death toll in part because the
people in the region built their homes out of loess. The loess
formed an easily excavated material that hundreds of thousands
of villagers cut homes into, essentially living in caves.
When the earthquake struck, the loess proved to be a poor
building material and large-scale collapse of the fine-grained
loess was directly responsible for most of the high death toll.
Recently, it has been recognized that windblown dust
contributes significantly to global climate. Dust storms that
come out of the Sahara can be carried around the world and
can partially block some of the Sun’s radiation. The dust particles
may also act as small nuclei for raindrops to form
around, perhaps acting as a natural cloud-seeding phenomenon.
One interesting point to ponder is that as global
warming increases global temperatures, the amount and
intensity of storms increase, and some of the world’s deserts
expand. Dust storms may serve to reduce global temperatures
and increase precipitation. Might the formation of dust
storms represent some kind of self-regulating mechanism,
whereby the Earth moderates its own climate?
See also DESERT; LOESS.
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