Grasslands are categorized by their climates and are either tropical or temperate. Tropical grasslands -- also known as savannas -- are found in Africa, South America, Australia and India where the climate is hotter and rainfall is between 20 and 50 inches every year.
North America is home to temperate grasslands, characterized by a lack of trees and large shrubs. The climate is one of seasonal extremes causing the strong winds typical of these interior areas. Winds are caused by any change in temperature and are typical prairie weather in both summer and winter.
In 1803, France sold most of the Great Plains and the Great Basin to the U.S. in the Louisiana Purchase. The land ran eastward from the Rocky Mountains through north-central Texas and west of the Rockies through Oregon, California and Idaho. According to the U.S. Forest Service, they are "wind-swept seas of grass and wildflowers." Many Native American tribes already lived on the grasslands but for the settlers this land was their final frontier. The 1862 Homestead Act guaranteed each settler farming plots on the grasslands and by 1890 six million people had moved in.
Grassland soil is rich in nutrients and benefits from the below-ground growth and decay of the grasses. The mass of decomposed roots not only feeds living plants but also binds the dark soil. Settlers replaced the grasses with agricultural crops, producing a great yield during wet seasons. During droughts and harsh winters, however, strong winds blew the fertile top soil away. Ten-foot-high banks of soil built up and clogged up the farms, causing mayhem on the settlements. The dust clouds reached up to 20,000 feet in the air over seven states.
The Dust Bowl of the 1930s decimated the American grasslands and lasted nearly 10 years. Previously abundant fertile ground offered up nothing during the droughts of the early '30s and farms were drenched in dust by indiscriminate windstorms.
During extreme dry periods, grassland areas are likely to catch fire, which the strong winds quickly spread. Although frequent, these fires don't destroy the grasslands as they're blown at such a rapid speed they only kill the surface growth and avoid the roots. This creates perfect conditions for new spring plants and efficiently gets rid of dead ones.
U.S. grasslands are such a target for violent winds in a large area known as Tornado Alley. Tornadoes occur when cold polar air from Canada collides with warm air from the Gulf of Mexico on the flat terrain of the Great Plains.
