Sandstorms, or dust storms, turn day into night. They occur when two elements are present: high wind and loose sand or dust. There's no controlling the wind, but sometimes we can control how much dust is ready to be blown away. Nature has its own controls, which humans can either help or hurt.
The First Element: High Winds
Dust storms require high wind, such as a strong cold front of powerful, straight-line winds. A cold front can blow steady winds downward to displace warmer air at the surface. If the warm air is moist, thunderstorms may develop to shower the ground in advance of the cold wind. Thunderstorms might also create smaller, local dust storms from their own downdraft winds. But if the warm air is dry, the ground is also dry when the strong winds arrive.
The Second Element: Loose Dust
Soil, sand, and dust are loose where there's little vegetation to hold them down. They're prone to erosion and deposition by wind, called aeolian transport. Light topsoil flies before sand and grit. It forms hilly deposits of compacted dust and silt called loess, and sand dunes, found around the world. Trade winds carry dust from the Sahara to the Amazon rain forests, where it provides mineral nutrients to the rain forests growing on poor soil.
The Dust Bowl is an Outstanding Example
The Dust Bowl in 1930s America combined several factors: "Sod busters" were farmers who broke the prairie sod that held the rich soil together. A period of extended drought dried the soil, and strong cold front winds blew the soil away. Meanwhile the Depression cut the agricultural market. Farms failed and more than a million people fled west to find work. Congress created the Soil Erosion Service to help farmers with methods to reduce their soil's exposure to wind and water erosion.
Natural and Artificial Defenses
Sand and silt deposits will move unless there's enough vegetation to hold them in place. The Great Plains provide an example of a blanket of sod that holds the soil, unless it's disturbed. Even in dry conditions, "desert pavement" forms a surface crust of interlocking gravel. But again, it fails when disturbed. Artificial soil conservation includes reformed farming practices like no-till and cover crops. These can't prevent storm conditions, but they can minimize storm damage.
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