An area of the Great Plains that experienced droughts and dust storms in the 1930s

Methods of growing crops in dry areas using only rainwater

Substance such as paint, plastic, cloth, insulation, or pesticide

A factory where crude oil is made into petroleum products

A fossil fuel the formed underground from dead plants

A small flat-topped hill

Deep narrow valley with steep sides

A layer of rock or gravel that traps water underground

A larger flat landform that rises steeply above the surrounding land; smaller than a plateau

Petroleum as it comes out of the ground

The buying and selling of goods between countries

Changes made over time by a species of plants or animals allowing it to survive in an environment