SPACEPHOTOS

The snow-covered Sierra Nevada, seen in this south-looking, low-oblique photograph, is the largest fault-block mountain range in the United States. Extending northwest-southeast, the mountain range, 400 miles (645 kilometers) long and 40 to 80 miles (65 to 130 kilometers) wide, rises sharply on its eastern side from the Great Basin, whereas its western slope descends gradually to the hills bordering the Central Valley of California (visible in the southwest corner of the photograph). Snow-fed streams supply irrigation water and generate hydroelectricity for the Central Valley and western Nevada. To the east of the Sierra Nevada, the western portions of the Great Basin can be seen. Aptly named because it sits between the Sierra Nevada to the west and the high Colorado Plateau and Wasatch Range to the east (not included in the photograph), the Great Basin comprises many smaller basins separated by fault-block mountain ranges rising 2000 to 3000 feet (600 to 900 meters) above the alluvium-filled floors of the basins. Three small bluish-colored lakes can be seen in the photograph. The southern portion of Lake Tahoe is barely discernible in the northwest corner of the photograph. East-southeast of Lake Tahoe is Walker Lake, and Mono Lake lies southeast of Lake Tahoe (near the center of the photograph).