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GEOGRAPHY OF THE UNITED STATES
The United States is situated almost entirely in the western hemisphere: the
contiguous United States stretches from the Pacific on the west to the Atlantic
on the east, with the Gulf of Mexico to the southeast, and bordered by Canada on
the north and Mexico on the south. Alaska is the largest state in area;
separated from the contiguous U.S. by Canada, it touches the Pacific on the
south and Arctic Ocean on the north. Hawaii occupies an archipelago in the
central Pacific, southwest of North America. The United States is the world's
third or fourth largest nation by total area, before or after China, depending
on how two territories disputed by China and India are counted; including only
land area, the United States is third in size behind Russia and China, just
ahead of Canada. The United States also possesses several insular territories
scattered around the West Indies (e.g., the commonwealth of Puerto Rico) and the
Pacific (e.g., Guam).
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 land of the Great Plains stretches to the west. The Rocky
Mountains, at the western edge of the Great Plains, extend north to south across
the continental United States, reaching altitudes higher than 14,000 feet (4,300
m) in Colorado. The area to the west of the Rocky Mountains is dominated by the
rocky Great Basin and deserts such as the Mojave. The Sierra Nevada range runs
parallel to the Rockies, relatively close to the Pacific coast. At 20,320 feet
(6,194 m), Alaska's Mount McKinley is the country's tallest peak. Active
volcanoes are common throughout the Alexander and Aleutian Islands, and the
entire state of Hawaii is built upon tropical volcanic islands. The supervolcano
underlying Yellowstone National Park in the Rockies is the continent's largest
volcanic feature.
Because of the United States' large size and wide range of geographic
features, nearly every type of climate is represented. The climate is temperate
in most areas, tropical in Hawaii and southern Florida, polar in Alaska,
semi-arid in the Great Plains west of the 100th meridian, desert in the
Southwest, Mediterranean in Coastal California, and arid in the Great Basin.
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
continental United States, primarily in the Midwest.
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