Geography, climate, and environment

Main articles: Geography of the United States, Climate of the United States, and Environment of the United States

A composite satellite image of the contiguous United States

The land area of the contiguous United States is 2,959,064 square miles (7,663,941 km²). Alaska, separated from the contiguous United States by Canada, is the largest state at 663,268 square miles (1,717,856 km²). Hawaii, occupying an archipelago in the central Pacific, southwest of North America, is 10,931 square miles (28,311 km²) in area.^[143]

The United States is the world's third or fourth largest nation by total area (land and water), ranking behind Russia and Canada and just above or below China. The ranking varies depending on how two territories disputed by China and India are counted and how the total size of the United States is measured: calculations range from 3,676,486 square miles (9,522,055 km²)^[144] to 3,717,813 square miles (9,629,091 km²)^[145] to 3,794,101 square miles (9,826,676 km²).^[4] Measured by only land area, the United States is third in size behind Russia and China, just ahead of Canada.^[146]

The coastal plain of the Atlantic seaboard gives way further inland to deciduous forests and the rolling hills of the Piedmont. The Appalachian Mountains divide the eastern seaboard from the Great Lakes and the grasslands of the Midwest. The Mississippi–Missouri River, the world's fourth longest river system, runs mainly north–south through the heart of the country. The flat, fertile prairie of the Great Plains stretches to the west, interrupted by a highland region in the southeast.

A Bald Eagle, the national bird of the United States since 1782.

The Rocky Mountains, at the western edge of the Great Plains, extend north to south across the country, reaching altitudes higher than 14,000 feet (4,300 m) in Colorado. Farther west are the rocky Great Basin and deserts such as the Chihuahua and Mojave. The Sierra Nevada and Cascade mountain ranges run close to the Pacific coast, both ranges reaching altitudes higher than 14,000 feet (4,300 m). The lowest and highest points in the continental United States are in the state of California, and only about 80 miles (130 km) apart. At 20,320 feet (6,194 m), Alaska's Mount McKinley is the tallest peak in the country and in North America. Active volcanoes are common throughout Alaska's Alexander and Aleutian Islands, and Hawaii consists of volcanic islands. The supervolcano underlying Yellowstone National Park in the Rockies is the continent's largest volcanic feature.^[147]

The United States, with its large size and geographic variety, includes most climate types. To the east of the 100th meridian, the climate ranges from humid continental in the north to humid subtropical in the south. The southern tip of Florida is tropical, as is Hawaii. The Great Plains west of the 100th meridian are semi-arid. Much of the Western mountains are alpine. The climate is arid in the Great Basin, desert in the Southwest, Mediterranean in coastal California, and oceanic in coastal Oregon and Washington and southern Alaska. Most of Alaska is subarctic or polar. Extreme weather is not uncommon—the states bordering the Gulf of Mexico are prone to hurricanes, and most of the world's tornadoes occur within the country, mainly in the Midwest's Tornado Alley.^[148]

The U.S. ecology is considered "megadiverse": about 17,000 species of vascular plants occur in the contiguous United States and Alaska, and over 1,800 species of flowering plants are found in Hawaii, few of which occur on the mainland.^[149] The United States is home to more than 400 mammal, 750 bird, and 500 reptile and amphibian species.^[150] About 91,000 insect species have been described.^[151]

There are 58 national parks and hundreds of other federally managed parks, forests, and wilderness areas.^[152] Altogether, the government owns 28.8% of the country's land area.^{[153][dead link]} Most of this is protected, though some is leased for oil and gas drilling, mining, logging, or cattle ranching; 2.4% is used for military purposes.^{[153][dead link][154][155]}

Date: 2015-12-17; view: 924