Dust is a collection of microscopic particles of material. Dust is heavy enough to see and light enough to be carried by the wind.
Dust can be made up of pollen, bacteria, smoke, ash, salt crystals from the ocean, and small bits of dirt or rock, including sand. Dust can also contain tiny fragments of human and animal skin cells, pollution, and hair.
When its windy outside, you can see dust particles blowing through the atmosphere. Large amounts of dust that are carried through the atmosphere by strong winds are called dust storms. Dust storms mostly occur in dry, open areas.
The Sahara Desert in Africa has many dust storms. Most Sahara dust is made of sand. Dust storms in the Sahara Desert can blow a wall of dust as high as one mile off the ground. Dust storms can make it very difficult to see and breathe.
In 1983, a dust storm covered the city of Melbourne, Australia. The deserts of Australia were experiencing drought, so sand and soil were loose. The dry conditions allowed about 50,000 tons of material to erode as dust. Melbourne had more than 1,000 tons of dust dumped on it. The dust caused so much damage that it took years of work and millions of dollars to repair.
Individual particles of dust are a major part of cloud condensation nuclei (CCN). Cloud condensation nuclei are made up of tiny pieces of solid material in clouds. CCN could be a dust storm drifting through a cloud, or an updraft with dust particles in it. Water vapor in the clouds condenses, or turns to liquid, around CCN. Invisible dust is often at the center of every raindrop.
In some areas, windblown dust settles into deposits called loess. Loess is a type of sediment that is loose and fragmented. It can be many meters deep. Loess often develops into fertile soil for agriculture because it retains water, allows many different plants to take root, and has abundant nutrients.
The Great Plains of the United States and Canada experienced severe drought during the 1930s. This drought came after years of agricultural development that did not include crop rotation. Very few plants anchored the soil. Crops were difficult to plant and, often, impossible to harvest. Dust storms were so strong, and so frequent, the entire area was called the Dust Bowl.
Dust Bowl storms could reduce visibility to a few feet, and had names like "Black Blizzards." Millions of farmers, especially those in the U.S. states of Oklahoma, Arkansas, and Texas, lost their land when they were unable to harvest any crops. These victims of the Dust Bowl migrated to places like California and Florida, where agricultural land was less affected by the dust storms and drought.
in large amounts.
modern farming methods that include mechanical, chemical, engineering and technological methods. Also called industrial agriculture.
the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).
to hold firmly in place.
(atm) unit of measurement equal to air pressure at sea level, about 14.7 pounds per square inch. Also called standard atmospheric pressure.
(singular: bacterium) single-celled organisms found in every ecosystem on Earth.
microscopic bits of clay, salt, or solid pollutant around which water vapor condenses in clouds to form raindrops.
to turn from gas to liquid.
the system of changing the type of crop in a field over time, mainly to preserve the productivity of the soil.
dry earth or soil.
period of greatly reduced precipitation.
tiny, dry particles of material solid enough for wind to carry.
(1930-1940) term for the Great Plains of the U.S. and Canada when severe dust storms forced thousands of people off their farms.
weather pattern of wind blowing dust over large regions of land.
to wear away.
person who cultivates land and raises crops.
able to produce crops or sustain agriculture.
grassland region of North America, between the Rocky Mountains and the Mississippi River.
thin strands of material covering the bodies of some animals, including humans.
the gathering and collection of crops, including both plants and animals.
a single thing.
state of matter with no fixed shape and molecules that remain loosely bound with each other.
windblown soil or silt.
substance an organism needs for energy, growth, and life.
large body of salt water that covers most of the Earth.
small piece of material.
powdery material produced by plants, each grain of which contains a male gamete capable of fertilizing a female ovule.
introduction of harmful materials into the environment.
to lower or lessen.
natural substance composed of solid mineral matter.
world's largest desert, in north Africa.
single particle of salt, or sodium chloride.
small, loose grains of disintegrated rocks.
solid material transported and deposited by water, ice, and wind.
soft external covering of some animals.
gases given off by a burning substance.
rising movement of gas.
visible liquid suspended in the air, such as fog.
the ability to see or be seen with the unaided eye. Also called visual range.
movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.