География и площадь Соединенных Штатов Америки

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The term "United States," when used in the geographical sense, refers to the contiguous United States (sometimes referred to as the Lower 48, including the District of Columbia), Alaska, Hawaii, the five insular territories of Puerto Rico, Northern Mariana Islands, U. S. Virgin Islands, Guam, American Samoa, and minor outlying possessions. The United States shares land borders with Canada and Mexico and maritime borders with Russia, Cuba, The Bahamas, and many other countries, mainly in the Caribbeanin addition to Canada and Mexico. The northern border of the United States with Canada is the world's longest bi national land border.

From 1989 through 1996, the total area of the US was listed as (land and inland water only). The listed total area changed to in 1997 (Great Lakes area and coastal waters added), to in 2004, to in 2006, and to in 2007 (territorial waters added). Currently, the CIA World Factbook gives , the United Nations Statistics Division gives , and the Encyclopedia Britannica gives (Great Lakes area included but not coastal waters). These sources consider only the 50 states and the Federal District and exclude overseas territories. The US has the 2nd largest Exclusive Economic Zone of
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. Both countries 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 the US calculates its surface area. Since the initial publishing of the World Factbook, the CIA has updated the total area of the United States several times.

The United States shares land borders with Canada to the north and Mexico to the south, 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 48 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; Hawaii lies far to the southwest of the mainland in the Pacific Ocean. The northern part of the United States (Canada) is located in the Canada Arctic Archipelago, the largest archipelago in the world. It is located near the Arctic 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 included in the term "continental United States", is located at the northwestern end of North America. The nation's capital city, Washington, D. C., was established in 1800 after being relocated there from Philadelphia. It was established as a federal district located on land donated by the state of Maryland; Virginia also donated land, but it was returned in 1849. The United States also has overseas territories with varying levels of autonomy and organization, including the Caribbean territories of Puerto Rico and the U. S. Virgin Islands, formerly known as the Danish Virgin Islands and purchased by the United States at the beginning of World War II, the Pacific territories of American Samoa, Guam and the Northern Mariana Islands, and several uninhabited island territories. Some of the territories acquired were part of the territorial evolution of the United States or a product of the nation's effort to gain access to the east. Nearly all of the United States is in the Northern Hemisphere with the exception of American Samoa and Jarvis Island.

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, continental in the north, 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 US in the winter months. The jet stream brings in large low pressure systems from the northern Pacific Ocean that enters 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 via the orographic effect, and they are greatly diminished by the time they reach the High Plains. Once they move over the Great Plains, uninterrupted flat land allows them 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, 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 The Southwest is a hot desert, with temperatures exceeding 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 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 and the deep southern states is 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 worldwide. 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 (2 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.

In northern Alaska, tundra and arctic conditions predominate, and the temperature has fallen as low as On the other end of the spectrum, Death Valley, California once reached , the highest temperature ever recorded on Earth. 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 ; the record there was in the winter of 1971–72. This record was broken by the Mt. Baker Ski Area in northwestern Washington which reported of snowfall for the 1998–99 snowfall season. Other places with significant snowfall outside the Cascade Range are the Wasatch Mountains in Utah, the San Juan Mountains in Colorado, and the Sierra Nevada in California. In the east, the region near the Great Lakes and the mountains of the Northeast receive the most snowfall, although they 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 Hawaii receives even more, with measured annually in the Big Bog, in Maui. Pago Pago Harbor in American Samoa is the rainiest harbor in the world (because of the 523 meter Rainmaker Mountain). In central portions of the U. S., tornadoes are more common than anywhere else on Earth 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. The West is affected by large wildfires each year.

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 substantially depopulated, and dust storms ravaged the land.

According to a 2023 Gallup survey, around one in three Americans said that they directly experienced a severe weather condition over the previous two years. 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. 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 formation 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. The U. S. territories and possessions in the Caribbean, including Puerto Rico and the U. S. Virgin Islands, are also vulnerable to hurricanes due to their location in the Caribbean Sea. 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 and Hurricane Maria in 2017. Hurricanes (known as cyclones in the Pacific Ocean) fail to make 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.

Occasional severe flooding is experienced in the United States. Significant floods throughout history include 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 flash floods as well, which can sometimes be devastating, while nor'easter snowstorms can bring activity to a halt throughout the Northeast (although heavy snowstorms can occur almost anywhere).

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. 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 have exceeded a magnitude of 5.6, and no one has been killed.

Other natural disasters include tsunamis around the Pacific Basin, mudslides 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 dust storms, beginning in the southern Great Plains and reaching to the Atlantic Ocean.

According to report by U. S. Census Bureau, in 2022 natural disasters led to the forced displacement of 3.3 million people, more than 1.3% of the U. S. adult population, with half of the displacements being caused by the hurricanes. The survey report stated that in Florida, the devastation caused by Hurricanes Ian and Nicole resulted in the relocation of around 1 million people, or about one in every 17 adult residents. In Louisiana, where inhabitants were still dealing with the devastating results of Hurricane Ida the year before, more than 409,000 people, or almost one in every eight residents, were moved. Despite this, the Louisiana state saw a relatively calm hurricane season in 2022.

In terms of human geography, the United States is inhabited by a diverse set of ethnicities and cultures.