III Natural Resources and Climate

Natural Resources

●Minerals and Metals

The United States is a land rich in natural resources. Many minerals are found in North America. Iron, nickel（鎳）, copper, gold, and many other metals are found in the North of the Great Lakes. Coal is found in eastern United States. Oil is found near the Gulf of Mexico. More metals—including lead, zinc（鋅）, and silver—are found in the western mountains. The US ranks first in the world in coal and natural gas deposits, and ranks second in the oil deposits.

●Forests

Before European settlement, forests covered nearly one billion acres of what is now the United States. Since the mid-1600's, about 300 million acres of forest have been cleared, primarily for agriculture during the 19th century. Today about one-third of the nation is forested. Total forest area has been relatively stable for the last 100 years（currently about 747 million acres）. Forests are chiefly found in the eastern and western highlands of the country. Along the Pacific coast there are more thick forests. The heavy rainfall there helps the trees to grow very large. This is the home of giant trees like the redwoods of California. Redwood trees often grow to be 61—91 meters tall. But in the Southwest, there are deserts where only small shrubs and cacti can grow.

Climate

Climates throughout the United States are as varied as its geographical features. It is mostly temperate, but tropical in Hawaii and Florida, arctic in Alaska, semiarid（半干旱的）in the great plains west of the Mississippi River, and arid in the Great Basin of the southwest. Most of the nation experiences all four seasons, with cold and snow winters and warm summers. The southwest and southeast experience fewer variations in climate and rarely receive snow in the winter.

The United States are exposed to various natural hazards: tsunamis（海嘯）, volcanoes, and earthquake activity around Pacific Basin; hurricanes along the Atlantic and Gulf of Mexico coasts; tornadoes（龍卷風）in the Midwest and southeast; mud slides in California; forest fires in the west; flooding; permafrost in northern Alaska.