Droughts

Its ____________________ are subtle and slow , the earth ____________________ , water levels ____________________ , the rains do not come , and the land is ____________________ by drought .
At its most basic , a drought occurs when more water is ____________________ than is ____________________ . It is a balance between ____________________ and ____________________ with both natural and human factors in ____________________ .
The weather is constantly in ____________________ . A low - pressure system allows ____________________ air to ____________________ , ____________________ and form ____________________ ____________________ . A high - pressure system traps the air beneath it and ____________________ the clouds . Droughts form when changing wind ____________________ cause high - pressure systems to ____________________ for months or even years .
Aggravating the problem is society's demand for water . Farms are heavily dependent on water to irrigate ____________________ and provide pasture for ____________________ . Urban areas also place huge demands on available water ____________________ . If the demand can't be reduced , then the drought begins to take its ____________________ . Crops eventually ____________________ and die , soil erodes away into clouds of ____________________ . Forest fires spread rapidly . The ____________________ to the environment has large - scale ____________________ for its human population . Short - term droughts cause stress on both the environment and people . Long - term droughts can lead to war , ____________________ , disease or mass ____________________ .
In the 1930s a ____________________ drought in the Great Plains caused massive crop ____________________ . In some places the drought lasted ____________________ years . So much soil blew away it became known as the ? dust ball ? . Over ____________________ million acres of land were affected forcing many farmers to ____________________ their own property . But by historical standards the ? dust ball ? was mild and short - lived . Some droughts have lasted for decades . The famines they create have killed over ____________________ million people in the 20th century alone .
Like other forms of ____________________ , droughts are one of the Earth's natural ____________________ . There is very little we can do to stop them . The best we can do is ____________________ for when droughts do come before everything blows away .