• dust
    Farmers lose tons of topsoil to dust.

    Photograph by Raymond Gehman

    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.

    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.

  • Term Part of Speech Definition Encyclopedic Entry
    abundant Adjective

    in large amounts.

    agricultural development Noun

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

    agriculture Noun

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

    Encyclopedic Entry: agriculture
    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.

    bacteria 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.

    crop Noun

    agricultural produce.

    Encyclopedic Entry: crop
    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.

    drought Noun

    period of greatly reduced precipitation.

    Encyclopedic Entry: drought
    dust Noun

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

    Encyclopedic Entry: dust
    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.

    loess Noun

    windblown soil or silt.

    Encyclopedic Entry: loess
    microscopic Adjective

    very small.

    nutrient Noun

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

    Encyclopedic Entry: nutrient
    ocean Noun

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

    Encyclopedic Entry: ocean
    particle Noun

    small piece of material.

    pollen Noun

    powdery material produced by plants.

    pollution Noun

    introduction of harmful materials into the environment.

    Encyclopedic Entry: pollution
    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.

    sediment Noun

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

    Encyclopedic Entry: sediment
    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.

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