Geography of the United States

The term "United States", when used in the geographical sense, is the contiguous United States, the state of Alaska, the island state of Hawaii, the five insular territories of Puerto Rico, Northern Mariana Islands, U.S. Virgin Islands, Guam, and American Samoa, and minor outlying possessions.[1] The United States shares land borders with Canada and Mexico and maritime borders with Russia, Cuba, and the Bahamas in addition to Canada and Mexico. The northern border of the United States with Canada is the world's longest bi-national land border.

Geography of The United States
USA topo en
ContinentNorth America
Coordinates38°00′00″N 97°00′00″W / 38.000°N 97.000°W
AreaRanked 3rd
 • Total9,826,675 km2 (3,794,100 sq mi)
 • Land93.24%
 • Water6.76%
Coastline19,920 km (12,380 mi)
BordersCanada: 8,864 km (5,508 mi)
Mexico: 3,327 km (2,067 mi)
Highest pointDenali/Mount McKinley
6,190.5 m (20,310 ft)
Lowest pointBadwater Basin,
−85 m (−279 ft)
Longest riverMissouri River,
3,767 km (2,341 mi)
Largest lakeLake Superior
58,000 km2 (22,394 sq mi)
ClimateDiverse: Ranges from Temperate in the North to Tropical in the far south. West: mostly semi-arid to desert, Mountains: alpine, Northeast: humid continental, Southeast: humid subtropical, Coast of California: Mediterranean, Pacific Northwest: cool temperate oceanic, Alaska: mostly subarctic, Hawaii, South Florida, and the territories: tropical
TerrainVast central plain, Interior Highlands and low mountains in Midwest, mountains and valleys in the mid-south, coastal flatland near the Gulf and Atlantic coasts, complete with mangrove forests and temperate, subtropical, and tropical laurel forest and jungle, canyons, basins, plateus, and mountains in west, hills and low mountains in east; intermittent hilly and mountainous regions in Great Plains, with occasional badland topography; rugged mountains and broad river valleys in Alaska; rugged, volcanic topography in Hawaii and the territories
Natural Resourcescoal, copper, lead, molybdenum, phosphates, rare earth elements, uranium, bauxite, gold, iron, mercury, nickel, potash, silver, tungsten, zinc, petroleum, natural gas, timber, arable land
Natural Hazardstsunamis; volcanoes; earthquake activity around Pacific Basin; hurricanes along the Atlantic and Gulf of Mexico coasts; tornadoes in the Midwest and Southeast; mud slides in California; forest fires in the west; flooding; permafrost in northern Alaska
Environmental Issuessevere water shortages, air pollution resulting in acid rain in both the US and Canada

Area

From 1989 through 1996, the total area of the US was listed as 9,372,610 km2 (3,618,780 sq mi) (land + inland water only). The listed total area changed to 9,629,091 km2 (3,717,813 sq mi) in 1997 (Great Lakes area and coastal waters added), to 9,631,418 km2 (3,718,711 sq mi) in 2004, to 9,631,420 km2 (3,718,710 sq mi) in 2006, and to 9,826,630 km2 (3,794,080 sq mi) in 2007 (territorial waters added). Currently, the CIA World Factbook gives 9,826,675 km2 (3,794,100 sq mi),[2] the United Nations Statistics Division gives 9,629,091 km2 (3,717,813 sq mi),[3] and the Encyclopædia Britannica gives 9,522,055 km2 (3,676,486 sq mi)(Great Lakes area included but not coastal waters).[4] These sources consider only the 50 states and the Federal District, and exclude overseas territories.

By total area (water as well as land), the United States is either slightly larger or smaller than the People's Republic of China, making it the world's third or fourth largest country. China and the United States are smaller than Russia and Canada in total area, but are larger than Brazil. By land area only (exclusive of waters), the United States is the world's third largest country, after Russia and China, with Canada in fourth. Whether the US or China is the third largest country by total area depends on two factors: (1) The validity of China's claim on Aksai Chin and Trans-Karakoram Tract. Both these territories are also claimed by India, so are not counted; and (2) How US calculates its own surface area. Since the initial publishing of the World Factbook, the CIA has updated the total area of United States a number of times.[5]

General characteristics

USA-satellite
A satellite composite image of the contiguous United States. Deciduous vegetation and grasslands prevail in the east, transitioning to prairies, boreal forests, and the Rockies in the west, and deserts in the southwest. In the northeast, the coasts of the Great Lakes and Atlantic seaboard host much of the country's population.
HawaiiGeography
A satellite composite image of the state of Hawaii. Volcanoes prevail on the Big Island. The islands have rugged coastlines, sandy beaches and a tropical environment, although temperatures and humidity tend to be less extreme because of near-constant trade winds from the east.

The United States shares land borders with Canada (to the north) and Mexico (to the south), and a territorial water border with Russia in the northwest, and two territorial water borders in the southeast between Florida and Cuba, and Florida and the Bahamas. The contiguous forty-eight states are otherwise bounded by the Pacific Ocean on the west, the Atlantic Ocean on the east, and the Gulf of Mexico to the southeast. Alaska borders the Pacific Ocean to the south and southwest, the Bering Strait to the west, and the Arctic Ocean to the north, while Hawaii lies far to the southwest of the mainland in the Pacific Ocean.

Forty-eight of the states are in the single region between Canada and Mexico; this group is referred to, with varying precision and formality, as the contiguous United States, and as the Lower 48. Alaska, which is not included in the term contiguous United States, is at the northwestern end of North America, separated from the Lower 48 by Canada, and instead is included in the term continental United States.

The capital city, Washington, District of Columbia, is a federal district located on land donated by the state of Maryland. (Virginia had also donated land, but it was returned in 1849.) The United States also has overseas territories with varying levels of independence and organization: in the Caribbean the territories of Puerto Rico and the U.S. Virgin Islands, and in the Pacific the inhabited territories of Guam, American Samoa, and the Northern Mariana Islands, along with a number of uninhabited island territories. Some of the territories acquired were a part of United States imperialism, or to gain access to the east.

Physiographic divisions

MountMcKinley BA
Denali, Alaska, the highest point in North America at 20,310 ft (6,190.5 m).

The eastern United States has a varied topography. A broad, flat coastal plain lines the Atlantic and Gulf shores from the Texas-Mexico border to New York City, and includes the Florida peninsula, which is home to some of the most beautiful beaches in the world. This broad coastal plain and barrier islands make up the widest and longest beaches in the United States, much of it composed of soft, white sands. The Florida Keys are a string of coral islands that reach the southernmost city on the United States mainland (Key West). Areas further inland feature rolling hills, mountains, and a diverse collection of temperate and subtropical moist and wet forests. Parts of interior Florida and South Carolina are also home to sand-hill communities. The Appalachian Mountains form a line of low mountains separating the eastern seaboard from the Great Lakes and the Mississippi Basin. New England features rocky seacoasts and rugged mountains with peaks up to 6200 feet and valleys dotted with rivers and streams. Offshore Islands dot the Atlantic and Gulf coasts.

The five Great Lakes are located in the north-central portion of the country, four of them forming part of the border with Canada, only Lake Michigan situated entirely within United States. The southeast United States, generally stretching from the Ohio River on south, includes a variety of warm temperate and subtropical moist and wet forests, as well as warm temperate and subtropical dry forests nearer the Great Plains in the west of the region. West of the Appalachians lies the lush Mississippi River basin and two large eastern tributaries, the Ohio River and the Tennessee River. The Ohio and Tennessee Valleys and the Midwest consist largely of rolling hills, interior highlands and small mountains, jungly marsh and swampland near the Ohio River, and productive farmland, stretching south to the Gulf Coast. The Midwest also has a vast amount of cave systems.

The Great Plains lie west of the Mississippi River and east of the Rocky Mountains. A large portion of the country's agricultural products are grown in the Great Plains. Before their general conversion to farmland, the Great Plains were noted for their extensive grasslands, from tallgrass prairie in the eastern plains to shortgrass steppe in the western High Plains. Elevation rises gradually from less than a few hundred feet near the Mississippi River to more than a mile high in the High Plains. The generally low relief of the plains is broken in several places, most notably in the Ozark and Ouachita Mountains, which form the U.S. Interior Highlands, the only major mountainous region between the Rocky Mountains and the Appalachian Mountains.[6][7]

The Great Plains come to an abrupt end at the Rocky Mountains. The Rocky Mountains form a large portion of the Western U.S., entering from Canada and stretching nearly to Mexico. The Rocky Mountain region is the highest region of the United States by average elevation. The Rocky Mountains generally contain fairly mild slopes and wider peaks compared to some of the other great mountain ranges, with a few exceptions (such as the Teton Mountains in Wyoming and the Sawatch Range in Colorado). The highest peaks of the Rockies are found in Colorado, the tallest peak being Mount Elbert at 14,440 ft (4,400 m). In addition, instead of being one generally continuous and solid mountain range, it is broken up into a number of smaller, intermittent mountain ranges, forming a large series of basins and valleys.

West of the Rocky Mountains lies the Intermontane Plateaus (also known as the Intermountain West), a large, arid desert lying between the Rockies and the Cascades and Sierra Nevada ranges. The large southern portion, known as the Great Basin, consists of salt flats, drainage basins, and many small north-south mountain ranges. The Southwest is predominantly a low-lying desert region. A portion known as the Colorado Plateau, centered around the Four Corners region, is considered to have some of the most spectacular scenery in the world. It is accentuated in such national parks as Grand Canyon, Arches, Mesa Verde and Bryce Canyon, among others. Other smaller Intermontane areas include the Columbia Plateau covering eastern Washington, western Idaho and northeast Oregon and the Snake River Plain in Southern Idaho.

Grand Canyon from Moran Point.jpeg
The Grand Canyon from Moran Point. The Grand Canyon is among the most famous locations in the country.

The Intermontane Plateaus come to an end at the Cascade Range and the Sierra Nevada. The Cascades consist of largely intermittent, volcanic mountains, many rising prominently from the surrounding landscape. The Sierra Nevada, further south, is a high, rugged, and dense mountain range. It contains the highest point in the contiguous 48 states, Mount Whitney (14,505 ft or 4,421 m). It is located at the boundary between California's Inyo and Tulare counties, just 84.6 mi or 136.2 km west-northwest of the lowest point in North America at the Badwater Basin in Death Valley National Park at 279 ft or 85 m below sea level.[8]

These areas contain some spectacular scenery as well, as evidenced by such national parks as Yosemite and Mount Rainier. West of the Cascades and Sierra Nevada is a series of valleys, such as the Central Valley in California and the Willamette Valley in Oregon. Along the coast is a series of low mountain ranges known as the Pacific Coast Ranges.

Alaska contains some of the most dramatic and untapped scenery in the country. Tall, prominent mountain ranges rise up sharply from broad, flat tundra plains. On the islands off the south and southwest coast are many volcanoes. Hawaii, far to the south of Alaska in the Pacific Ocean, is a chain of tropical, volcanic islands, popular as a tourist destination for many from East Asia and the mainland United States.

The territories of Puerto Rico and the U.S. Virgin Islands encompass a number of tropical isles in the northeastern Caribbean Sea. In the Pacific Ocean the territories of Guam and the Northern Mariana Islands occupy the limestone and volcanic isles of the Mariana archipelago, and American Samoa (the only populated US territory in the southern hemisphere) encompasses volcanic peaks and coral atolls in the eastern part of the Samoan Islands chain.

Physiographic regions

US physiographic map
A physiographical map of the contiguous 48 states of the U.S. The map indicates the age of the exposed surface as well as the type of terrain.

The geography of the United States varies across its immense area. Within the continental U.S., eight distinct physiographic divisions exist, though each is composed of several smaller physiographic subdivisions.[9] These major divisions are:

Scipio Township near Republic
Much of the central United States is covered by relatively flat, arable land. This aerial photo was taken over northern Ohio.

The Atlantic coast of the United States is low, with minor exceptions. The Appalachian Highland owes its oblique northeast-southwest trend to crustal deformations which in very early geological time gave a beginning to what later came to be the Appalachian mountain system. This system had its climax of deformation so long ago (probably in Permian time) that it has since then been very generally reduced to moderate or low relief. It owes its present-day altitude either to renewed elevations along the earlier lines or to the survival of the most resistant rocks as residual mountains. The oblique trend of this coast would be even more pronounced but for a comparatively modern crustal movement, causing a depression in the northeast resulting in an encroachment of the sea upon the land. Additionally, the southeastern section has undergone an elevation resulting in the advance of the land upon the sea.

While the Atlantic coast is relatively low, the Pacific coast is, with few exceptions, hilly or mountainous. This coast has been defined chiefly by geologically recent crustal deformations, and hence still preserves a greater relief than that of the Atlantic. The low Atlantic coast and the hilly or mountainous Pacific coast foreshadow the leading features in the distribution of mountains within the United States.

The east coast Appalachian system, originally forest covered, is relatively low and narrow and is bordered on the southeast and south by an important coastal plain. The Cordilleran system on the western side of the continent is lofty, broad and complicated having two branches, the Rocky Mountain System and the Pacific Mountain System. In between these mountain systems lie the Intermontaine Plateaus. Both the Columbia River and Colorado River rise far inland near the easternmost members of the Cordilleran system, and flow through plateaus and intermontaine basins to the ocean. Heavy forests cover the northwest coast, but elsewhere trees are found only on the higher ranges below the Alpine region. The intermontane valleys, plateaus and basins range from treeless to desert with the most arid region being in the southwest.

The Laurentian Highlands, the Interior Plains and the Interior Highlands lie between the two coasts, stretching from the Gulf of Mexico northward, far beyond the national boundary, to the Arctic Ocean. The central plains are divided by a hardly perceptible height of land into a Canadian and a United States portion. It is from the United States side, that the great Mississippi system discharges southward to the Gulf of Mexico. The upper Mississippi and some of the Ohio basin is the semi-arid prairie region, with trees originally only along the watercourses. The uplands towards the Appalachians were included in the great eastern forested area, while the western part of the plains has so dry a climate that its native plant life is scanty, and in the south it is practically barren.

Elevation extremes:

Climate

Average precipitation in the lower 48 states of the USA
A map of average precipitation across the contiguous US.

Due to its large size and wide range of geographic features, the United States contains examples of nearly every global climate. The climate is subtropical in the Southern United States, tropical in Hawaii and southern Florida, polar in Alaska, semiarid in the Great Plains west of the 100th meridian, Mediterranean in coastal California and arid in the Great Basin and the Southwest. Its comparatively favorable agricultural climate contributed (in part) to the country's rise as a world power, with infrequent severe drought in the major agricultural regions, a general lack of widespread flooding, and a mainly temperate climate that receives adequate precipitation.

The main influence on U.S. weather is the polar jet stream which migrates northward into Canada in the summer months, and then southward into the USA in the winter months. The jet stream brings in large low pressure systems from the northern Pacific Ocean that enter the US mainland over the Pacific Northwest. The Cascade Range, Sierra Nevada, and Rocky Mountains pick up most of the moisture from these systems as they move eastward. Greatly diminished by the time they reach the High Plains, much of the moisture has been sapped by the orographic effect as it is forced over several mountain ranges.

Once it moves over the Great Plains, uninterrupted flat land allows it to reorganize and can lead to major clashes of air masses. In addition, moisture from the Gulf of Mexico is often drawn northward. When combined with a powerful jet stream, this can lead to violent thunderstorms, especially during spring and summer. Sometimes during winter these storms can combine with another low pressure system as they move up the East Coast and into the Atlantic Ocean, where they intensify rapidly. These storms are known as Nor'easters and often bring widespread, heavy rain, wind, and snowfall to New England. The uninterrupted grasslands of the Great Plains also lead to some of the most extreme climate swings in the world. Temperatures can rise or drop rapidly and winds can be extreme, and the flow of heat waves or Arctic air masses often advance uninterrupted through the plains.

The Great Basin and Columbia Plateau (the Intermontane Plateaus) are arid or semiarid regions that lie in the rain shadow of the Cascades and Sierra Nevada. Precipitation averages less than 15 inches (38 cm). The Southwest is a hot desert, with temperatures exceeding 100 °F (37.8 °C) for several weeks at a time in summer. The Southwest and the Great Basin are also affected by the monsoon from the Gulf of California from July to September, which brings localized but often severe thunderstorms to the region.

Much of California consists of a Mediterranean climate, with sometimes excessive rainfall from October–April and nearly no rain the rest of the year. In the Pacific Northwest rain falls year-round, but is much heavier during winter and spring. The mountains of the west receive abundant precipitation and very heavy snowfall. The Cascades are one of the snowiest places in the world, with some places averaging over 600 inches (1,524 cm) of snow annually, but the lower elevations closer to the coast receive very little snow.

Florida has a subtropical climate in the northern part of the state and a tropical climate in the southern part of the state. Summers are wet and winters are dry in Florida. Annually much of Florida, as well as the deep southern states, are frost-free. The mild winters of Florida allow a massive tropical fruit industry to thrive in the central part of the state, making the US second to only Brazil in citrus production in the world.

Another significant (but localized) weather effect is lake-effect snow that falls south and east of the Great Lakes, especially in the hilly portions of the Upper Peninsula of Michigan and on the Tug Hill Plateau in New York. The lake effect dumped well over 5 feet (1.52 m) of snow in the area of Buffalo, New York throughout the 2006-2007 winter. The Wasatch Front and Wasatch Range in Utah can also receive significant lake effect accumulations from the Great Salt Lake.

Extremes

In northern Alaska, tundra and arctic conditions predominate, where the temperature has fallen as low as −80 °F (−62.2 °C).[10] On the other end of the spectrum, Death Valley, California once reached 134 °F (56.7 °C), the highest temperature ever recorded on Earth.[11][12]

On average, the mountains of the western states receive the highest levels of snowfall on Earth. The greatest annual snowfall level is at Mount Rainier in Washington, at 692 inches (1,758 cm); the record there was 1,122 inches (2,850 cm) in the winter of 1971–72. This record was broken by the Mt. Baker Ski Area in northwestern Washington which reported 1,140 inches (2,896 cm) of snowfall for the 1998-99 snowfall season. Other places with significant snowfall outside the Cascade Range are the Wasatch Mountains, near the Great Salt Lake, the San Juan Mountains in Colorado, and the Sierra Nevada, near Lake Tahoe.

In the east, the region near the Great Lakes and the mountains of the Northeast receive the most snowfall, although such snowfall levels do not near snowfall levels in the western United States. Along the northwestern Pacific coast, rainfall is greater than anywhere else in the continental U.S., with Quinault Rainforest in Washington having an average of 137 inches (348 cm).[13] Hawaii receives even more, with 404 inches (1,026 cm) measured annually in the Big Bog, in Maui. The Mojave Desert, in the southwest, is home to the driest locale in the U.S. Yuma, Arizona, has an average of 2.63 inches (6.7 cm) of precipitation each year.[14]

In central portions of the U.S., tornadoes are more common than anywhere else on Earth[15] and touch down most commonly in the spring and summer. Deadly and destructive hurricanes occur almost every year along the Atlantic seaboard and the Gulf of Mexico. The Appalachian region and the Midwest experience the worst floods, though virtually no area in the U.S. is immune to flooding. The Southwest has the worst droughts; one is thought to have lasted over 500 years and to have hurt Ancestral Pueblo peoples.[16] The West is affected by large wildfires each year.

Natural disasters

The United States is affected by a variety of natural disasters yearly. Although drought is rare, it has occasionally caused major disruption, such as during the Dust Bowl (1931–1942). Farmland failed throughout the Plains, entire regions were virtually depopulated, and dust storms ravaged the land.

Dimmitt Tornado1 - NOAA
A powerful tornado near Dimmitt, Texas on June 2, 1995.

Tornadoes and hurricanes

The Great Plains and Midwest, due to the contrasting air masses, see frequent severe thunderstorms and tornado outbreaks during spring and summer with around 1,000 tornadoes occurring each year.[17] The strip of land from north Texas north to Kansas and Nebraska and east into Tennessee is known as Tornado Alley, where many houses have tornado shelters and many towns have tornado sirens due to the very frequent tornado formations in the region.

Hurricanes are another natural disaster found in the US, which can hit anywhere along the Gulf Coast or the Atlantic Coast as well as Hawaii in the Pacific Ocean. Particularly at risk are the central and southern Texas coasts, the area from southeastern Louisiana east to the Florida Panhandle, peninsular Florida, and the Outer Banks of North Carolina, although any portion of the coast could be struck.

Hurricane season runs from June 1 to November 30, with a peak from mid-August through early October. Some of the more devastating hurricanes have included the Galveston Hurricane of 1900, Hurricane Andrew in 1992, Hurricane Katrina in 2005, and Hurricane Harvey in 2017.

Hurricanes (known as cyclones in the Pacific Ocean) fail to landfall on the Pacific Coast of the United States due to water temperatures being too cool to sustain them. However, the remnants of tropical cyclones from the Eastern Pacific occasionally impact the western United States, bringing moderate to heavy rainfall.

Hurricane katrina damage gulfport mississippi
Total devastation in Gulfport, Mississippi caused by storm surge from Hurricane Katrina in 2005.

Flooding

Occasional severe flooding is experienced. There was the Great Mississippi Flood of 1927, the Great Flood of 1993, and widespread flooding and mudslides caused by the 1982–83 El Niño event in the western United States. Flooding is still prevalent, mostly on the Eastern Coast, during hurricanes or other inclement weather, for example in 2012, when Hurricane Sandy devastated the region. Localized flooding can, however, occur anywhere, and mudslides from heavy rain can cause problems in any mountainous area, particularly the Southwest. Large stretches of desert shrub in the west can fuel the spread of wildfires. The narrow canyons of many mountain areas in the west and severe thunderstorm activity during the summer lead to sometimes devastating flash floods as well, while nor'easter snowstorms can bring activity to a halt throughout the Northeast (although heavy snowstorms can occur almost anywhere).

Geologic

The West Coast of the continental United States makes up part of the Pacific Ring of Fire, an area of heavy tectonic and volcanic activity that is the source of 90% of the world's earthquakes. The American Northwest sees the highest concentration of active volcanoes in the United States, in Washington, Oregon and northern California along the Cascade Mountains. There are several active volcanoes located in the islands of Hawaii, including Kilauea in ongoing eruption since 1983, but they do not typically adversely affect the inhabitants of the islands. There has not been a major life-threatening eruption on the Hawaiian islands since the 17th century. Volcanic eruptions can occasionally be devastating, such as in the 1980 eruption of Mount St. Helens in Washington.

The Ring of Fire makes California and southern Alaska particularly vulnerable to earthquakes. Earthquakes can cause extensive damage, such as the 1906 San Francisco earthquake or the 1964 Good Friday earthquake near Anchorage, Alaska. California is well known for seismic activity, and requires large structures to be earthquake resistant to minimize loss of life and property.[18] Outside of devastating earthquakes, California experiences minor earthquakes on a regular basis.

There have been about 100 significant earthquakes annually from 2010 to 2012. Past averages were 21 a year. This is believed to be due to the deep disposal of wastewater from fracking. None has exceeded a magnitude of 5.6, and no one has been killed.[19]

Other natural disasters

Other natural disasters include: tsunamis around Pacific Basin, mud slides in California, and forest fires in the western half of the contiguous U.S. Although drought is relatively rare, it has occasionally caused major economic and social disruption, such as during the Dust Bowl (1931–1942), which resulted in widespread crop failures and duststorms, beginning in the southern Great Plains and reaching to the Atlantic Ocean.

Public lands

Territorial waters - United States
Exclusive economic zones of the United States, including insular areas

The United States holds many areas for the use and enjoyment of the public. These include National Parks, National Monuments, National Forests, Wilderness areas, and other areas. For lists of areas, see the following articles:

See also

Notes

  1. ^ U.S. State Department, Common Core Document to U.N. Committee on Human Rights, December 30, 2011, Item 22, 27, 80; Homeland Security Public Law 107-296 Sec.2.(16)(A); Presidential Proclamation of national jurisdiction [1]
  2. ^ "United States". The World Factbook. CIA. 2009-09-30. Retrieved 2010-01-05.
  3. ^ "Population by Sex, Rate of Population Increase, Surface Area and Density" (PDF). Demographic Yearbook 2005. UN Statistics Division. Retrieved 2008-03-25.
  4. ^ "United States". Encyclopædia Britannica. Retrieved 2008-03-25.
  5. ^ Countries of the World: 21 Years of World Facts, geographic.org, retrieved 2008-08-17
  6. ^ "Managing Upland Forests of the Midsouth". United States Forestry Service. Archived from the original on 2007-10-17. Retrieved 2007-10-13.
  7. ^ "A Tapestry of Time and Terrain: The Union of Two Maps - Geology and Topography". United States Geological Survey. Archived from the original on 2006-05-15. Retrieved 2007-10-13.
  8. ^ "USGS National Elevation Dataset (NED) 1 meter Downloadable Data Collection from The National Map 3D Elevation Program (3DEP) - National Geospatial Data Asset (NGDA) National Elevation Data Set (NED)". United States Geological Survey. September 21, 2015. Retrieved September 22, 2015.
  9. ^ "Physiographic Regions". United States Geological Survey. 2003-04-17. Archived from the original on 2006-05-15. Retrieved 2008-01-30.
  10. ^ Williams, Jack Each state's low temperature record, USA today, URL accessed 13 June 2006.
  11. ^ "Weather and Climate" (PDF). Official website for Death Valley National Park. National Park Service U. S. Department of the Interior. January 2002. pp. 1–2. Retrieved October 5, 2006.
  12. ^ "WMO Press release No. 956". World Meteorological Organization. September 13, 2012. Archived from the original on April 6, 2016. Retrieved April 10, 2016.
  13. ^ National Atlas, Average Annual Precipitation, 1961-1990 Archived 2006-09-28 at the Wayback Machine, URL accessed 15 June 2006.
  14. ^ Hereford, Richard, et al., Precipitation History of the Mojave Desert Region, 1893–2001, U.S. Geological Survey, Fact Sheet 117-03, URL accessed 13 June 2006.
  15. ^ NOVA, Tornado Heaven, Hunt for the Supertwister, URL accessed 15 June 2006.
  16. ^ O'Connor, Jim E. and John E. Costa, Large Floods in the United States: Where Thley Happen and Why, U.S. Geological Survey Circular 1245, URL accessed 13 June 2006.
  17. ^ NSSL: Severe Weather 101. Nssl.noaa.gov. Retrieved on 2013-07-29.
  18. ^ https://earthquake.usgs.gov/learn/publications/saferstructures/
  19. ^ Vergano, Dan (July 12, 2013). "Study:Earthquake increase tied to energy boom". The Burlington Free Press. Burlington, Vermont. pp. 10A. Retrieved July 14, 2013.

Further reading

  • Brown, Ralph Hall, Historical Geography of the United States, New York : Harcourt, Brace, 1948
  • Stein, Mark, How the States Got Their Shapes, New York : Smithsonian Books/Collins, 2008. ISBN 978-0-06-143138-8

External links

Coordinates: 38°00′00″N 97°00′00″W / 38.000°N 97.000°W

California Land Act of 1851

The California Land Act of 1851 (9 Stat. 631), enacted following the Treaty of Guadalupe Hidalgo and the admission of California as a state in 1850, established a three-member Public Land Commission to determine the validity of prior Spanish and Mexican land grants. It required landowners who claimed title under the Mexican government to file their claim with a commission within two years. Contrary to the Treaty of Guadalupe Hidalgo, which guaranteed full protection of all property rights for Mexican citizens, it placed the burden on landholders to prove their title.

While the commission eventually confirmed 604 of the 813 claims, almost all of the claims went to court and resulted in protracted litigation. The expense of the long court battles required many land holders to sell portions of the property or even trade it in payment for legal services. A few cases were litigated into the 1940s.

Collar counties

The expression the collar counties is a colloquialism for the five counties of Illinois that border Chicago's Cook County. After Cook County, they are also the next five most populous counties in the state. According to the Encyclopedia of Chicago, there is no specifically known origin of the phrase, but it has been commonly used among policy makers, urban planners, and in the media. However, it also notes that as growth has spread beyond these counties, it may have lost some of its usefulness.The collar counties (DuPage, Kane, Lake, McHenry, and Will) are tied to Chicago economically. However, like many other suburban areas in the United States, the collar counties have very different political leanings from the core city. Chicago has long been a Democratic stronghold, but the collar counties are known for being historically Republican strongholds, although they have recently become more politically diverse.

While the demographics of these suburban Chicago counties are fairly typical for American metropolitan areas, the term is apparently unique to this area. Also, because Cook County is so firmly entrenched in the Democratic column, and rural Downstate is overwhelmingly Republican, the collar counties are routinely cited as being the key to any statewide election. However, that conventional wisdom was challenged in 2010 as Democrat Pat Quinn won election as governor while only winning Cook, St. Clair, Jackson and Alexander counties. All five collar counties went Republican, so the key to winning that gubernatorial election was simply winning Cook County, but by a wide enough margin to overwhelm the rest of the state.While the term is often employed in political discussions, that is not its exclusive use. Barack Obama used the term in his speech before the Democratic National Convention in 2004.As of 2010 there are 3,143,257 people residing in the collar counties, nearly 25% of the population of Illinois. Combined with Cook County the area has approximately 65% of Illinois's population.

Continental Divide of the Americas

The Continental Divide (also known as the Great Divide, Western Continental Divide or more elaborately, the Continental Divide of the Americas) is the principal, and largely mountainous, hydrological divide of the Americas. The Continental Divide extends from the Bering Strait to the Strait of Magellan, and separates the watersheds that drain into the Pacific Ocean from those river systems that drain into the Atlantic Ocean (including those that drain into the Gulf of Mexico and the Caribbean Sea) and, along the northernmost reaches of the Divide, those river systems that drain into the Arctic Ocean.

Though there are a few other hydrological divides in the Americas, the Continental Divide is by far the most prominent of these because it tends to follow a line of high peaks along the main ranges of the Rocky Mountains and Andes, at a generally much higher elevation than the other hydrological divisions.

Four Corners

The Four Corners is a region of the United States consisting of the southwestern corner of Colorado, southeastern corner of Utah, northeastern corner of Arizona, and northwestern corner of New Mexico. The Four Corners area is named after the quadripoint at the intersection of approximately 37° north latitude with 109° 03' west longitude, where the boundaries of the four states meet, and are marked by the Four Corners Monument. It is the only location in the United States where four states meet. Most of the Four Corners region belongs to semi-autonomous Native American nations, the largest of which is the Navajo Nation, followed by Hopi, Ute, and Zuni tribal reserves and nations. The Four Corners region is part of a larger region known as the Colorado Plateau and is mostly rural, rugged, and arid. In addition to the monument, commonly visited areas within Four Corners include Monument Valley, Mesa Verde National Park, Chaco Canyon, Canyons of the Ancients National Monument and Canyon de Chelly National Monument. The most populous city in the Four Corners region is Farmington, New Mexico, followed by Durango, Colorado.

Geographic Names Information System

The Geographic Names Information System (GNIS) is a database that contains name and locative information about more than two million physical and cultural features located throughout the United States of America and its territories. It is a type of gazetteer. GNIS was developed by the United States Geological Survey in cooperation with the United States Board on Geographic Names (BGN) to promote the standardization of feature names.

The database is part of a system that includes topographic map names and bibliographic references. The names of books and historic maps that confirm the feature or place name are cited. Variant names, alternatives to official federal names for a feature, are also recorded. Each feature receives a permanent, unique feature record identifier, sometimes called the GNIS identifier. The database never removes an entry, "except in cases of obvious duplication."

Geography of the United States Virgin Islands

Geography of the United States Virgin Islands

The United States Virgin Islands are a group of several dozen islands and cays located in the Caribbean, about 1,100 miles (1,770 km) southeast of Florida, 600 miles (966 km) north of Venezuela, 40 miles (64 km) east of Puerto Rico, and immediately west and south of the British Virgin Islands.

The U.S. Virgin Islands lie near the boundary of the North American Plate and the Caribbean Plate, roughly 100 miles (161 km) south of the Puerto Rico Trench and near the Anegada Passage, a key shipping lane. Together with the British Virgin Islands, Vieques, and Culebra, they make up the Virgin Islands archipelago.

The hilly, volcanic islands of Saint Thomas (31 square miles (80 km2)) and Saint John (20 square miles (52 km2)) border the North Atlantic Ocean to the north and the Caribbean Sea to the south. The larger island of Saint Croix (84 square miles (218 km2)) lies 40 miles (64 km) to the south across the Virgin Islands Trough and is entirely in the Caribbean Sea.

Charlotte Amalie, Saint Thomas is one of the best natural, deepwater harbors in the Caribbean. The Islands have many well-known beaches, including Magens Bay (Saint Thomas) and Trunk Bay (Saint John), and coral reefs, including the Virgin Islands Coral Reef National Monument and the Buck Island Reef National Monument. More than half of Saint John and nearly all of Hassel Island are owned by the U.S. National Park Service.

Crown Mountain, on Saint Thomas, is the highest point in the U.S. Virgin Islands. Sea level is the lowest.

Geology of the Rocky Mountains

The geology of the Rocky Mountains is that of a discontinuous series of mountain ranges with distinct geological origins. Collectively these make up the Rocky Mountains, a mountain system that stretches from Northern British Columbia through central New Mexico and which is part of the great mountain system known as the North American Cordillera.

The rocky cores of the mountain ranges are, in most places, formed of pieces of continental crust that are over one billion years old. In the south, an older mountain range was formed 300 million years ago, then eroded away. The rocks of that older range were reformed into the Rocky Mountains.

The Rocky Mountains took shape during an intense period of plate tectonic activity that resulted in much of the rugged landscape of the western North America. The Laramide orogeny, about 80–55 million years ago, was the last of the three episodes and was responsible for raising the Rocky Mountains. Subsequent erosion by glaciers has created the current form of the mountains.

Interior Plains

The Interior Plains is a vast physiographic region that spreads across the Laurentian craton of central North America. The region extends from the Gulf Coast region to the Arctic Ocean along the east flank of the Rocky Mountains. In Canada the region separates the Rocky Mountains from the Canadian Shield. In the United States the plains include the Great Plains of the west and the Tallgrass prairie region to the south of the Great Lakes extending east to the Appalachian Plateau region.

List of U.S. states and territories by area

This is a complete list of the U.S. states, federal district, and its major territories ordered by total area, land area, and water area. The water area includes inland waters, coastal waters, the Great Lakes, and territorial waters. Glaciers and intermittent bodies of water are counted as land area.

Old Southwest

The "Old Southwest" is an informal name for the southwestern frontier territories of the United States from the Revolutionary War era through the early 19th century, at the point when the territorial lands were organized into states.

The territory of the Old Southwest eventually formed the states of Missouri, Mississippi, Arkansas, Alabama, Louisiana, Texas, and parts of Tennessee, Kentucky, and Florida (panhandle).

Outer Continental Shelf

The Outer Continental Shelf (OCS) is a peculiarity of the political geography of the United States. The OCS is the part of the internationally recognized continental shelf of the United States which does not fall under the jurisdictions of the individual U.S. States.

Pacific Coast Ranges

The Pacific Coast Ranges (officially gazetted as the Pacific Mountain System in the United States but referred to as the Pacific Coast Ranges), are the series of mountain ranges that stretch along the West Coast of North America from Alaska south to Northern and Central Mexico.

The Pacific Coast Ranges are part of the North American Cordillera (sometimes known as the Western Cordillera, or in Canada, as the Pacific Cordillera and/or the Canadian Cordillera), which includes the Rocky Mountains, Columbia Mountains, Interior Mountains, the Interior Plateau, Sierra Nevada Mountains, the Great Basin mountain ranges, and other ranges and various plateaus and basins.

The Pacific Coast Ranges designation, however, only applies to the Western System of the Western Cordillera, which comprises the Saint Elias Mountains, Coast Mountains, Insular Mountains, Olympic Mountains, Cascade Range, Oregon Coast Range, California Coast Ranges, Transverse Ranges, Peninsular Ranges, and the Sierra Madre Occidental.

Plat

In the United States, a plat ( or ) (plan or cadastral map) is a map, drawn to scale, showing the divisions of a piece of land. United States General Land Office surveyors drafted township plats of Public Lands Surveys to show the distance and bearing between section corners, sometimes including topographic or vegetation information. City, town or village plats show subdivisions into blocks with streets and alleys. Further refinement often splits blocks into individual lots, usually for the purpose of selling the described lots; this has become known as subdivision.

After the filing of a plat, legal descriptions can refer to block and lot-numbers rather than portions of sections. In order for plats to become legally valid, a local governing body, such as a public works department, urban planning commission, or zoning board must normally review and approve them.

Purple America

Purple America is the belief that a more detailed analysis of the voting results of recent United States national elections reveals that the U.S. electorate is not as polarized between "Red" America (Republican) and "Blue" America (Democratic) as is often depicted in news analysis. The term reflects the fact that news organizations generally use the colors red and blue on maps to indicate when a state or congressional district has been won by a Republican or Democratic candidate, respectively. Because the American political system often awards a state or congressional district entirely to one candidate ("winner take all") without regard to the margin of victory, it results in a map that does not reflect the true distribution of "red" or "blue" votes across the nation. The distortions contained in these maps, the argument goes, contribute to the misperception that the electorate is highly polarized by geography.

Robert Vanderbei at Princeton University made the first Purple America map after the 2000 presidential election. It attempts to reflect the margin of victory in each county by coloring each with a shade between true blue and true red. In light of the general absence of overwhelming victories, this technique results in mostly shades. This map was reprinted in US News & World Report a few months prior to the 2004 election. After the 2004 election, Vanderbei and then others made similar maps summarizing the results. Quickly thereafter, the term Purple America permeated the political blogosphere and entered the public lexicon as a way of stating that the United States is not as divided as the political pundits would have the people believe.Cartograms developed by Gastner, Shalizi, and Newman at the University of Michigan provide another way to depict election results.

Subarctic

The subarctic is a region in the Northern Hemisphere immediately south of the true Arctic and covering much of Alaska, Canada, Iceland, the north of Scandinavia, Siberia, the Shetland Islands, and the Cairngorms. Generally, subarctic regions fall between 50°N and 70°N latitude, depending on local climates. Precipitation is low, and vegetation is characteristic of the taiga.

Time in the United States

Time in the United States, by law, is divided into nine standard time zones covering the states and its possessions, with most of the United States observing daylight saving time (DST) for approximately the spring, summer, and fall months. The time zone boundaries and DST observance are regulated by the Department of Transportation. Official and highly precise timekeeping services (clocks) are provided by two federal agencies: the National Institute of Standards and Technology (NIST) (an agency of the Department of Commerce); and its military counterpart, the United States Naval Observatory (USNO). The clocks run by these services are kept synchronized with each other as well as with those of other international timekeeping organizations.

It is the combination of the time zone and daylight saving rules, along with the timekeeping services, which determines the legal civil time for any U.S. location at any moment.

United States Board on Geographic Names

The United States Board on Geographic Names (BGN) is a federal body operating under the United States Secretary of the Interior. The purpose of the board is to establish and maintain uniform usage of geographic names throughout the federal government of the United States.

Virgin Islands

The Virgin Islands are geologically and biogeographically the easternmost part of the Greater Antilles, the northern islands belonging to the Puerto Rican Bank and St. Croix being a displaced part of the same geologic structure. Politically, the British Virgin Islands have been governed as the western island group of the Leeward Islands, which are the northern part of the Lesser Antilles, and form the border between the Caribbean Sea and the Atlantic Ocean. The archipelago is separated from the true Lesser Antilles by the Anegada Passage and from the main island of Puerto Rico by the Virgin Passage.

The islands fall into three different political jurisdictions:

British Virgin Islands, a British overseas territory,

United States Virgin Islands, an unincorporated territory of the United States,

Spanish (or Puerto Rican) Virgin Islands, the easternmost islands of the Commonwealth of Puerto Rico, itself an unincorporated territory of the United States.

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