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.

dust
Farmers lose tons of topsoil to dust.

Dust Bowl
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.

abundant
Adjective

in large amounts.

agricultural development
Noun

modern farming methods that include mechanical, chemical, engineering and technological methods. Also called industrial agriculture.

Noun

the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).

anchor
Verb

to hold firmly in place.

atmosphere (atm)
Noun

(atm) unit of measurement equal to air pressure at sea level, about 14.7 pounds per square inch. Also called standard atmospheric pressure.

Plural Noun

(singular: bacterium) single-celled organisms found in every ecosystem on Earth.

cloud condensation nuclei (CCN)
Plural Noun

microscopic bits of clay, salt, or solid pollutant around which water vapor condenses in clouds to form raindrops.

condense
Verb

to turn from gas to liquid.

Noun

agricultural produce.

crop rotation
Noun

the system of changing the type of crop in a field over time, mainly to preserve the productivity of the soil.

dirt
Noun

dry earth or soil.

Noun

period of greatly reduced precipitation.

Noun

tiny, dry particles of material solid enough for wind to carry.

Dust Bowl
Noun

(1930-1940) term for the Great Plains of the U.S. and Canada when severe dust storms forced thousands of people off their farms.

dust storm
Noun

weather pattern of wind blowing dust over large regions of land.

erode
Verb

to wear away.

farmer
Noun

person who cultivates land and raises crops.

fertile
Adjective

able to produce crops or sustain agriculture.

frequent
Adjective

often.

Great Plains
Noun

grassland region of North America, between the Rocky Mountains and the Mississippi River.

hair
Noun

thin strands of material covering the bodies of some animals, including humans.

harvest
Noun

the gathering and collection of crops, including both plants and animals.

individual
Adjective

a single thing.

liquid
Noun

state of matter with no fixed shape and molecules that remain loosely bound with each other.

Noun

windblown soil or silt.

microscopic
Adjective

very small.

Noun

substance an organism needs for energy, growth, and life.

Noun

large body of salt water that covers most of the Earth.

particle
Noun

small piece of material.

pollen
Noun

powdery material produced by plants, each grain of which contains a male gamete capable of fertilizing a female ovule.

Noun

introduction of harmful materials into the environment.

reduce
Verb

to lower or lessen.

rock
Noun

natural substance composed of solid mineral matter.

Sahara Desert
Noun

world's largest desert, in north Africa.

salt crystal
Noun

single particle of salt, or sodium chloride.

sand
Noun

small, loose grains of disintegrated rocks.

Noun

solid material transported and deposited by water, ice, and wind.

skin
Noun

soft external covering of some animals.

smoke
Noun

gases given off by a burning substance.

updraft
Noun

rising movement of gas.

vapor
Noun

visible liquid suspended in the air, such as fog.

visibility
Noun

the ability to see or be seen with the unaided eye. Also called visual range.

wind
Noun

movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.