Some of the highest mountains in the mainland United States are found in the range called the Sierra Nevada. It runs along the eastern edge of California, reaching also into western Nevada. Sierra Nevada means “snowy range.” Spanish settlers named the mountains after the Sierra Nevada in southern Spain.

Physical features

The mountains of the Sierra Nevada were formed by a massive uplifting of the Earth's crust that began many millions of years ago. Today the range is about 400 miles (640 kilometers) long. It extends from the Mohave Desert of southern California to the Cascade Range, which begins in northern California and runs northward through Oregon and Washington. On the west the Sierra Nevada slopes down to California's Central Valley. To the east is the rugged desert region called the Great Basin.

Most of the peaks in the Sierra Nevada reach heights of 11,000 to 14,000 feet (3,350 to 4,270 meters) above sea level. The highest is Mount Whitney at 14,494 feet (4,418 meters). It is the highest peak in the United States outside of Alaska.

A series of streams cuts through the range's west-facing slopes. Almost all of the western streams drain into either of two rivers in the Central Valley: the Sacramento in the north or the San Joaquin in the south. These rivers then join and empty into the Pacific Ocean.

At one time the Sierra Nevada region was covered by glaciers. These were so large that they formed an ice cap almost 200 miles (320 kilometers) long, from Lake Tahoe in the north to the southern peaks near Mount Whitney. Smaller glaciers extended from the ice cap, carving spectacular natural features. Among them are the many unusual circular valleys and glacial lakes of Yosemite National Park. The glaciers also formed Lake Tahoe, the largest mountain lake in the United States.

Climate

The climate of the Sierra Nevada is milder than that of many other mountain ranges of similar height. This is largely because of the influence of the nearby Pacific Ocean. Winds from the west bring warm air from the ocean to the mountains. These winds also carry a lot of moisture. Because the mountains act as a barrier to the winds, the western slopes receive much more rain and snow than the eastern slopes.

Plants and animals

The plant life of the Sierra Nevada varies based on factors such as elevation and precipitation. Different types of plants grow at different heights throughout the range, and the wet western slopes have different plants than the dry eastern slopes. The lower western foothills have mostly trees and shrubs that lose their leaves in autumn. At higher elevations are evergreens, which keep their leaves through the winter. The evergreens include cedars, pines, firs, and giant sequoias, which are the largest trees in the world. The eastern slopes have sagebrush, juniper, and aspen. On both the western and eastern slopes, trees cannot grow above a certain height—called the timberline, or the tree line—because of the climate. Only mosses, lichens, and low-flowering plants grow above this level.

As the human population in the Sierra Nevada area has grown, the number of large mammals has been reduced. The black bear is found over a large area, but grizzly bears are much rarer. Mountain sheep are found only in the southern part of the range. Mule deer and mountain lions live in the foothills. Among the smaller mammals of the mountain forests are the American badger, skunk, bobcat, golden beaver, and northern flying squirrel. The rich bird life includes the California horned lark, canyon wren, roadrunner, spotted owl, goshawk, and white-toed woodpecker.

Human presence

A number of Native American tribes once lived in the Sierra Nevada. They were hunters and gatherers. The first Europeans to come to the region were Spanish explorers and missionaries, who visited what is now California in the 18th century. In the early 19th century American hunters and fur trappers passed through the region. When gold nuggets were found in the mountain streams in 1848, the California gold rush began. Soon the Sierra Nevada was full of explorers and fortune-seekers from all over the world. Cities such as San Francisco sprang up nearby, and roads and railroads were cut into the mountains.

Economy

Although the activity spurred by the gold rush peaked by 1880, some mining still takes place in the Sierra Nevada. Agriculture contributes to the economy as well, with orchards and vineyards being especially valuable. Trees are cut down for timber. The most important part of the region's economy, however, is tourism. The Lake Tahoe area and three national parks—Yosemite, Kings Canyon, and Sequoia—draw people to the area year-round with their beautiful mountain scenery. Many of the visitors come from the huge urban areas of California.

Environmental issues

Since the start of the gold rush, human activities have altered the landscape of the Sierra Nevada. Mining and later logging and tourism have led to air and water pollution. Beginning in the second half of the 20th century, rapid population growth in the mountains added to the environmental concerns. Increased automobile use, for example, led to traffic jams and more air pollution. The expansion of human settlements also has led to habitat loss for the region's wildlife.