Terrain shapes and bedrock
The main features of the US topography are an older mountain range along the east side, a younger one along the west and a large and low area in between. In the latter, the Mississippi River with tributaries, primarily the Missouri River and the Ohio River, is a central lifeline. See also Alaska (Terrain forms and bedrock) and Hawaii (Terrain shapes and bedrock).
A significant landform region in the southern and eastern United States is the coastal plain. It is built up of young, loose sediments and reaches a maximum width of 800 km along the Gulf of Mexico. The coastal plain encompasses the entire Florida peninsula but decreases in breadth north along the Atlantic coast. The height does not exceed 100 m above sea level. and is in several places below 5 m above sea level. Flooded river valleys form estuaries (estuaries), e.g. Chesapeake Bay and Delaware Bay. Sand reefs, beach spurs and beach lakes with marshlands within occur along large parts of the coast. Along the Gulf of Mexico there is plenty of sand dunes and delta.
According to COUNTRYAAH, the Appalachians are the mountain region that dominates the eastern United States and separates the Atlantic coastal plain from the interior of the country. It extends with a width of 200-500 km from Alabama in the south about 2,400 km northeast to the Canada border. It originated during the Varian rock chain formation (see Varian orogenesis) and has been eroded by erosion to an average height of approximately 1,100 m above sea level. The highest peak, Mount Mitchell, 2,037 m above sea level, lies on Blue Ridge, a long narrow mountain ridge that slopes eastwards steeply down to the wavy surface of the Piedmont Plateau.
The Piedmont Plateau is in turn bounded by a sharp steep slope from the coastal plain. To the west of the Blue Ridge runs a long valley, the Great Valley, and to the west there is an area with curved and heavily eroded sand and limestone ridges. At the far west is the Appalachian Plateau, where the Allegheny Mountains form a high front. The Cumberland Plateau’s cool terrain then continues to the west as a transition to the interior of the United States.
The Inner Plains are the largest landform region in the United States. It reaches from the coastal plain in the south to Canada and the Great Lakes and has a width that is far greater in the north, about 2,800 km compared to 600 km in the south. The substrate is sedimentary rocks from the Paleozoic and Mesozoic, when the area was water covered, except in the Adirondack Mountains in the northeast and around the Upper Lake where the uplands are located. Inland ice during the recent ice age reached as far south as the Ohio River and the Missouri Riverand has left tracks in the form of moraine blankets, moraine ridges and sea-filled sinks. South and west of these, vast areas of loose soil are spreading. The eastern part of the Inner Plains is called Central Lowlands and reaches from Texas to New York State. There are also some higher plateaus such as the Ozark Plateau. The Great Plains form an 800–1,000 km wide belt in the western plains of the Inner Plains. The plains form wavy plateaus that gradually rise from about 600 to about 2,000 m above sea level. The ground surface is in many places strongly eroded with deep cut ravines, so-called badlands.
The Cordillarians occupy the western third of the United States. They are part of a system of active mountain ranges and arches extending around the Pacific. Within the United States, the two main branches, where the eastern branch, the Rocky Mountains, comprise a large number of mountain ranges with peaks up to close to 4,400 meters above sea level.
The western branch is the coastal mountains closest to the sea. Inside them lies the Central Valley, a deep burial ground drained by the Sacramento River and the San Joaquin River. On the eastern side of the valley, the Sierra Nevada rises to the south and the Cascade Mountains further north. Here is the US highest peak outside Alaska, Mount Whitney 4,418 m asl. The mountains to the north are mainly of volcanic origin. Between the two mountain range branches spreads in the southern Colorado Plateau, consisting of sedimentary rocks and flooded rivers, e.g. The Colorado River with the Grand Canyon. To the west and north lies the Great Basin with, among other things.Stora Saltsjön, largely a steppe and desert area. At the far north is the Columbia Plateau with large lava fields and several rivers. Columbia River and Snake River. The Cordillarians continue through Canada to Alaska, where the US highest mountain Denali (to 2015 Mount McKinley, 6,194 m above sea level). Off the western coast of Alaska lies the volcanic archipelago of Aleutians. Even Hawaii in the Pacific Ocean are a volcanic archipelago.
Within such an extensive area as the United States, there are several different types of climate. The country’s openness in the north-south direction, ie. the absence of large mountain ranges in the east – west direction, means that the continental character of the climate is strengthened as warm air masses penetrate far north in summer and cold far south in winter. It is only the Pacific coast, and to a lesser extent the coasts of the Gulf of Mexico and the Atlantic south of Virginia, which has a more temperate climate of the sea.
North of latitude about 40 ° there is a cold-temperate humid climate, except in the high-lying terrain around the Rocky Mountains, which have a drier steep climate. The eastern United States south of latitude about 40 ° has a warm temperate humid climate. To the west of the longitude about 100 °, the precipitation is low, below 500 mm per year, which is why arid climates such as desert and steppe climates prevail. These are more extreme in the southern parts of the country. The northern Pacific coast has a maritime climate with rain in winter and an average summer temperature of 16-18 °C, in Alaska 10-15 °C. In Alaska’s northern and upland regions, polar climate prevails, while the Hawaiian archipelago has a near-tropical, oceanic climate.
In the continental United States of the Northeast, the weather can vary rapidly throughout the year; both the temperature variations and the precipitation amounts are more extreme than in Europe. Heat waves during the summer can cause temperatures of almost 40 °C, while the winter can be very cold and snowy.
According to BRIDGAT, the weather is becoming milder towards the southeastern states and Florida has a near tropical climate where frost and snow rarely occur. The Atlantic’s smoothing effect means that summer temperatures here will not be as high as further north. The average temperature during the summer months is usually 25-30 °C. The humid and warm climate makes thunderstorms more common further south; In Florida, thunderstorms occur during nearly a third of the year’s days. Tropical cyclones occur at least a couple of times a year between July and October.
The northern central parts of the United States have the most continental climate with cold winters and hot summers with heat waves and droughts, especially in the west. The winter rainfall is low and falls mainly as snow, and storms with very cold northern winds occur. The sunshine hours are plentiful, even during the winter. On the eastern side of the Rocky Mountains, the wind chinook local winds can quickly melt the snow during winter and spring.
The weather in the southern central states is relatively similar to the farther north, but the latitude difference makes the winters both warmer and shorter. Summers are slightly warmer than farther north, but above all, summer is longer and spring and autumn are warmer. The eastern parts of this region are most rainy, over 1,000 mm per year against less than 500 mm per year in the west, and warm thunderstorms are very common. The Gulf of Mexico states are often and severely affected by tropical storms during the summer.
The states along the Klippiga mountains experience a relatively dry climate with large local variations due to altitude and terrain differences. The climate is much cooler in the north than in the south throughout the year and is generally also rainier. The southern regions have desert or steppe climate with long, dry and hot summers and mild winters. The annual rainfall in some places is as low as 200 mm due to the rain shadow from the western mountains of California and the stable summer high pressure over the area. The southern part is also the sunniest in the entire United States, with eight hours of sunshine daily during the winter and up to thirteen hours during the summer. Even though the humidity is low, the high daytime temperatures, usually above 40 degrees in summer in low-lying terrain, can be troublesome. In winter, rainfall can occur as snow even in the desert,
The states in the northwest of the continental United States have a climate similar to northwest Europe because of the Pacific Ocean’s temperature-compensating effect and numerous low pressure from the northern Pacific polar front. The coastal districts have the smallest temperature variation during the year, with mild winters and only moderately warm summers. The region is the cloudiest and least sunny in the entire United States. Winter is the rainiest season and significant summer drought is rare. The annual precipitation varies between only 300 mm in protected valleys and high plateaus, to 3,000 mm on the windward side of the mountain massif in the western Kordiljars.
California enjoys a distinctive Mediterranean climate with significantly higher temperatures and lower precipitation than the northern Pacific states. Most of California has relatively mild and moderately rainy winters and hot or hot, very dry summers. The higher terrain in Sierra Nevada is rainy and much of the rainfall falls as snow. The San Francisco area is known for the dense fog that occasionally drifts in from the ocean and which rarely affects the coastal areas. The desert areas in the southeast are among the hottest and driest on earth. The steady high pressure that over the southern parts of California in the summer also causes harmful levels of air pollution in the Los Angeles area, which cannot normally be dissolved due to the surrounding mountain heights.
The climate in the United States is extremely diverse. There are several climate zones, such as the continental, subtropical, Mediterranean and in southern Florida tropical climate.
The northern regions, from Washington State to Maine, have a moderate, temperate climate. Winters can be very cool (values below 0 ° C are not uncommon) – in summer, however, heat waves with temperatures above 35 ° C can often occur. The amount of precipitation is evenly distributed over the whole year; the winters are always accompanied by snowfall. The highest temperature ever recorded in New York was 43 ° C, while the lowest was only -26 ° C.
The climate changes the further south you look: if it is still cool and temperate in the north, then in the southern states one speaks of a subtropical climate – for example in Texas, Louisiana, Mississippi, Georgia and large parts of Florida. The south of Florida, including the Keys, is already tropical with rainy and dry seasons. Since the state of California borders directly on the Pacific Ocean, this zone is known as the Mediterranean climate.
Plant-and animal life
The United States exhibits an impressive wealth of nature and still has large, relatively untouched wilderness areas where nature is allowed to take care of itself. The country extends from the subtropical Caribbean in the south to Arctic Alaska in the north and, in between, exhibits a wide variety of different habitats, including large desert areas, prairies, miles of forests, large lakes and rivers, and high mountains.
On the surface, the United States is comparable to Europe, but exhibits a much more diverse plant and animal world. There, for example, four times as many amphibians, two and a half times as many herbivores, more than twice as many mammals and almost twice as many vascular plants as in Europe. This is largely due to the fact that the mountain ranges in the US run in a north-south direction and that plant and animal species were therefore able to move without major barriers in connection with climate change. In Europe, on the other hand, where most of the mountain ranges run in an east-west direction (the Alps, Pyrenees, Carpathians and the Caucasus), the topography and the Mediterranean posed insurmountable obstacles to many species in connection with the icing, which led to many dying out.
The eastern United States is dominated by the Appalachian mountain range. The most important natural area is the National Park in the Great Smoky Mountains. Although the park is only 200,000 ha, there are almost as many tree species as in Europe. The pristine, leafy forests house several, ancient plant species that survived the recent ice ages, and the diversity of temperate species is unparalleled in the United States. The abundant rainfall creates a wealth of waterways with more than 70 different fish species and many different amphibians. The area is famous for its 30 different species of salamanders, probably the largest concentration of different species in the world. Among the mammals are the wolf, black bear, vapiti (white-tailed deer), white-tailed deer and smaller North American flying squirrel (seeflying squirrels). The rich bird life includes rare species such as virginiauv (Bubo virginianus) and blue-white forest singer (Setophaga cerulea) – the latter with the largest decline among all migratory North American birds.
Along the east coast between Maryland and Virginia lies the country’s largest estuary, Chesapeake Bay, famous for its oyster banks and rich bird life. During the fall and spring, millions of waterfowl, about a million of them winter, pass through them, snow goose and smaller song swans. The nesting birds include osprey, white-headed sea eagle and the endangered flute-shore pair (Charadrius melodus). Species such as mallards, red-breasted merganser, great egrets and glossy ibis recognized from Europe. The Atlantic form of daggers tail (Limulus polyphemus, see daggers tail) gather in abundance in the spring and lay their eggs along the shores, although Delaware Bay further north is more famous for its daggers tails.
At the far south of the Florida peninsula is Everglades, a subtropical wilderness area with a large contiguous mangrove swamp famous for its alligators and crocodiles as well as nesting herons, ibis and other wetland birds. One of the strangest animals is the large mammal lamantine (see manatees) that lives on shallow water and eats seagrass. Other known animals in the Everglades are cougar and seashell.
At the extension of Key West, the archipelago that extends west from Florida’s southern tip, lies Dry Tortuga National Park. Tortuga means tortoise in Spanish and here there are no less than five nesting species of sea turtles – true sea turtle, illegitimate sea turtle, mushroom turtle, sea turtle and bastard turtle (Lepidochelys kempi). The breeding bird fauna confines itself to seven species, including: star tern, brown noddy and black noddy (Anous minutus), magnificent frigate bird (Freegate magnificens) and mask sole (Sula dactylatra). Amhaj (Ginglymostoma cirratum) patrolling the beach zone in search of fish and other bottom-living animals. The coral reef, with at least 30 different corals, two species of moose coral, is home to many colorful fish.
On the border between Arizona, California and Mexico is North America’s largest desert, Sonoran, with an area as large as Poland and a unique flora and fauna. There are several national parks, including Saguaro National Park in Arizona, which is named after the famous saguaro cactus (Carnegiea gigantea). This tall plant (up to 20 m) with its characteristic branches is up to 150 years old and, like older trees, offers protected nesting sites for a wide range of bird species. Two of the most important ones are sonoras (Colaptes chrysoides) and cacti (Melanerpes uropygialis) which cut out cavities in the cactus also suitable as habitats for many other species, e.g. cactus owl (Micrathene whitneyi), cactusCampylorhynchus brunneicapillus, see bats) and several species of flycatchers. The white or yellow flowers are pollinated by a special bat species (Leptonycteris yerbabuenae), which spends the summer months in the desert before moving south to Central America for the winter. Other mammals that live in Sonoran are kangaroo mice, large-tailed sheep, and coyotes.
Further north in Arizona is the Grand Canyon, one of America’s most well-known places with up to 1,600 m deep canyons and a very varied and rich plant and animal life. The hanging gardens, where water seeps from the mountain slopes, are famous for their rich flora. In the Colorado River, several rare fish live, and in addition to interesting amphibians and crawfish, the Grand Canyon is known for its many mammals: beaver, common cat feather (see cat ferrets), western blotch (see spot turtles), redfish, gray fox, black- tailed deer, and black- tailed deer. Among the birds, California condor is probably the most famous.
In central California is Yosemite National Park. One of the legendary advocates of wilderness protection – John Muir – found much inspiration here in the late 1800s, which laid the foundation for the national park’s creation in 1890. Yosemite attracts more than 3.5 million visitors each year. The dramatic landscape with five of the world’s highest waterfalls is the big draw. The remaining forests of mammoth trees are another attraction. There is also a coyote, wolverine, Snowshoe, fish marten, American marten (Martes americana), black bear, grizzly bear, and the yellow-bellied marmot (Marmota flaviventris). Among the birds are Spotted Owl (Strix occidentalis) one of the most significant. Due to its strong dependence on ancient forests, the species has become a symbol for the conservation of these highly threatened environments in western North America.
North of San Francisco is Redwood National Park, which has its name from the world’s tallest tree, the American Sequoia. In addition to the unique forest, the park protects a valuable coastal section with cliffs and wide sandy beaches. Here are colonies of seal seals and two species of sea lions. Gray Whale passes on its annual hike between the rejuvenation areas of Baja California and the Arctic waters off Alaska. If you are posted on the beaches during dawn or dusk, you can also witness the guard release of the marble morale (Brachyramphus marmoratus), which, unlike its closest relatives, nest high up in the crowns of the tree, sometimes up to 80 km from the coast. Other special birds are brown pelican, white-headed sea eagle, spotted owl and California Allen’s hummingbird (Selasphorus sasin).
In the borderland between Wyoming, Idaho and Montana lies Yellowstone National Park, famous for its geysers and its wild scenery and rich wildlife. With its 67 mammal species, Yellowstone National Park lacks its counterpart in the rest of North America. Here you will find bison, fork antelope, vapiti, wolf (re-implanted in 1995), wolverine, prairie wolf, cougar, black bear, elk, redfish, black-tailed deer, thick-horned sheep and the country’s most well-studied tribe of grizzly bears, with around 50 reproductive females each year. No less than seven different coniferous species grow within the national park and together with various deciduous trees create large forest areas. Natural forest fires occur every year and play an important role in the natural processes. Some tree species, including lodgepole pine, is even dependent on fire to put seeds. In 1988, Yellowstone was hit by very extensive fires in connection with an extremely hot and rainy summer, which caused more than a third of the park to be damaged by fire. Most of the affected areas have since recovered well and very few wildlife died in connection with the fire. Since 1988, however, stricter rules have been applied to limit human damage and spread outside the park boundaries.
The dental parts
Large parts of central North America were occupied before Europeans colonized the continent of vast prairies. The prairies were created by a combination of climate (hot dry summers, cold winters and eternal winds), large grass-eating animals (bison, vapiti and white-tailed deer) and regular fires. Today, after cultivation for agricultural purposes, barely a tenth of the original surface remains. One of the largest contiguous remaining prairie areas is the Badlands National Park in South Dakota, where approximately 100,000 have been deposited through an agreement with the Ogla Sioux Tribe. Here there are still herds of grazing bison, black-tailed deer, fork antelope and large-horned sheep. The many colonies of black-tailed prairie dogs (Cynomys ludovicianus) create conditions for the United States’ rarest and most endangered mammal, black-footed ferret (Mustela nigripes). After a dramatic decline of the prairie dog in connection with the ostensibly, the ferret’s food base disappeared, and during the 1970s it was considered extinct. In 1981, a small colony of 18 animals was found in Wyoming, and after an intensive breeding program, in 1991, the first 36 animals were released free, among other things. Badlands National Park. Today, the wild tribe is estimated at over 1,000 animals distributed in 18 different populations. Badlands National Park is also internationally renowned for its abundant fossil presence. of primitive mammals from the oligocene, over 23 million years ago.
The United States’ northernmost state of Alaska is famous for its wilderness areas. Wrangell-Saint Elias National Park in the southeast, adjacent to Yukon and British Columbia, Canada, is the United States largest national park with an area of 5.3 million ha or as large as Croatia. The park houses the country’s second highest mountain, Mount Saint Elias, large glaciers, forests, valleys and a varied coast. The mammals include grizzly bear, black bear, elk, caribou, wolf, American snow sheep, snow, Canadian lo, wolverine, bison, cougar, American otter (Lontra canadensis) and beaver. Along the coast are sea lions, seal seals, sea otters, porpoises and several whales. killer whale. The great variety of nature from the Pacific to the high alpine areas creates a rich bird fauna with, among other things. elk, ducks, swans, geese, waders, birds of prey and owls. Large numbers of Arctic migratory birds pass during spring and autumn.
In 2012, about 27% of the country’s land was protected in some form; inter alia there were 87 national parks federally managed by the National Park Service. Of the ten largest national parks, seven are located in Alaska, of which the largest is Wrangell-St. Elias with an area of 33 682 km2. Other major national parks include Yellowstone in Wyoming (8,991 km2), Everglades in Florida (5,859 km2), the Grand Canyon in Arizona (4,934 km2) and Glacier National Park in Montana (4,101 km2). The management of nature conservation is divided so that the National Park Service is responsible for the management of the protected areas while the US Fish and Wildlife Service is responsible for the individual species’ survival.