The USA Geography

The main landmass of the USA lies in central North America bor­dering Canada in the North and Mexico in the South, washed by the Atlantic Ocean in the East and the Pacific in the West. Alaska and Hawaii are separated from the continental United Sates, Hawaii is in the Central Pacific and Alaska is in the north-west of Canada.

The USA is a spacious country of varying terrains and climates. It stretches 2,575 km from north to south and 4,500 km from east to west. To get from New York to San Francisco one travels across regions of geographical extremes. There are forested mountains, fertile plains, arid deserts, canyon lands and wide plateaus between the coasts. A tremendous diversity in physical features and climate range from moist rain forests to arid deserts and prairies. Mountain McKinley in Alaska is the highest point in the USA while part of Death Valley in California is 89 metres below sea level. In the West the Cordillera, more than 1,000 miles wide in some places runs 4,500 miles from the Mexican border to the Appalachians linking with the mountainous country of New England.

The interior of the continent includes high plains next to the Cordillera and lowlands stretching to the Gulf of Mexico. The coastal plains are a long gently rolling lowland area. They stretch from Maine to Texas and are very flat in Florida, nowhere more than 350 feet above the sea level and often swampy. Parts of the USA may remind other countries. There are pine forests dotted with lakes and mountain peaks covered with snow, meadows with brooks and sea cliffs, wide grassy plains and sandy beaches.

Along the coasts of the Atlantic Ocean and the Gulf of Mexico is a coastal plain, almost all of it is below 100 m in altitude with an average width of 160—320 km widening only near the Mississippi River where it extends to Illinois. The shores of the plain are sandy with the exception of the muddy delta of the Mississippi. Sand reefs or barrier beaches form a straight outer coast from Long Island to Mexico. The coastal plain extends under water, under the Atlantic Ocean and the

Gulf of Mexico, more than 320 km forming the continental shelf. The water is rather shallow there.

The Atlantic Coastal Plain stretches from Cape Cod and Long Island to Florida. It is broadest in the south and narrower in the north. Once the Atlantic Coastal Plain was the land covered with pine trees. The coastline of the plain is irregular. Gradual sinking of the land in the past formed a great number of estuaries some of which are navigable for many kilometres in land, for example the Hudson River, the James, the Richmond. The largest inlet is Chesapeake Bay. Long Is­land, Martha's Vineyard, Nantucket Island, and Block Island are actu­ally tops of coastal plain hills.

Like a great thumb the peninsula of Florida extends from the Southeast into the sea for nearly 400 miles. The peninsula is the result of an uplift of the sea bottom. The southern part of the peninsula is so little above sea level, that the land is swampy. The most valuable part of it is a low limestone ridge on the Atlantic side with winter resorts on it.

The Atlantic Coastal Plain is separated from the Appalachian moun­tain system by the Fall Line. The Fall Line is an imaginary line joining waterfalls on rivers and streams that marks the limit of navigability. Water falls or rapids occur at the boundary between the hard rocks of the Appalachians and the softer plain.

In the past the Fall Line served the first frontier for American settlers. In the 18^th century the Americans began to move westward across the line. The waterfalls became important power resources and major cities developed along The Fall Line: Trenton, Philadelphia, Baltimore, Washington, and Richmond.

Almost parallel to the Atlantic Coastal Plain are the Appalachian Highlands that extend from Newfoundland to Alabama. The Appala­chians are the principle mountain system of the eastern USA that is 2,000 miles long and though has relatively low elevations makes up the dominant relief feature of the east. Low as they are the Appalachian mountains form a watershed between the streams that flow to the At­lantic Ocean and those that flow westward to the Mississippi. The Poto­mac, James and Roanoke rivers extend only partway through the High­lands.

The Appalachian Highlands are composed of four provinces: the Piedmont Plateau, the Blue Ridge, the Ridge and the Great Valley and the Appalachian plateau. A great number of mountain ranges lying almost parallel to each other like belts form the Appalachian mountain system. In the north across New Hampshire are the White Mountains. They stretch into west Maine. The white mountains have the highest peaks (with the exception of the Great Smokies). They got their name from the greyish white appearance of the higher peaks. Mount Wash­ington is 1,917 m high.

In Vermont The Green mountains extend 400 km from north to south, with the average elevation of 975 m. The slopes are gentle to­ward the Connecticut river on the east and sharply steep toward Lake Champlain on the west. The steep slopes limit farming to valley bot­toms. The mountains are forested; you can find beech, maple, spruce and evergreens.

Across the Hudson River from the Green mountains are the Ad­irondacks of New York State, an uplift of ancient crystalline rocks. The peaks range from 1000 to 1600 m. The forest covers a minor part of the mountains and is very varied.

West of the Hudson River in New York we find the Catskill moun­tains with rounded summits and bulky masses between them. There are few valleys but deep gorges called «cloves». There one can see a lot of waterfalls. The scenery is very picturesque. The Catskills are a resort area. Fenimore Cooper described the Catskills in his novels and they are home of legendary Rip Van Winkle, Washington living's hero. The highest peak rises to 1,220 m. The sloping summits are visible from the Hudson and present a striking view.

Farther south lies the Blue Ridge. It stretches from Pennsylvania to Georgia. The Roanoke river divides it into two parts. In North Carolina the Blue Ridge is much broader and merges with the Great Smoky mountains, the highest of the Appalachia system. The highest peak is Mount Mitchell 2,037 m. The bluish haze that hangs over the mountains gave them the name. The mountains are heavily forested with conifer­ous forests on higher levels and hardwood forests on lower levels. About one hundred species of trees can be found there. Famous Great Smoky Mountain National Park and the Cherokee Indian Reservation that attract thousands of tourists are situated in that area.

The Allegheny mountains extend from Pennsylvania to West Virginia. The peaks are all of nearly equal height, about 1,300 m high, only 300 m above the Allegheny plateaus, thus there are no typical valleys, but narrow pieces of dissected plateau.

In the Southwest of the Appalachian Highlands almost opposite the great Smokies are the Cumberland mountains, a continuation of the Alleghenies. The altitude is not great, just 450-600 m. The highest peak is Big Black mountain.

In the east bordering the Atlantic Coastal Plain is the Piedmont plateau, also part of the Appalachian Highlands. It extends from New York to Alabama. This hilly region is a highly productive agricultural area.

The Appalachian Trail, a marked footpath for recreation, stretch­es for 3,200 km. The Trail was built by volunteers in the 1920s-1930s. It runs from Mount Katahdin in Maine (1,607 m high), to Mount Spring­er in Georgia (1,164 m high), through fourteen States, eight national forests and two national parks.

Between the Rocky mountains on the west and the Appalachians on the east is a vast area of lowland. It comprises the Central Lowland and the Great Plains. The interior plains or lowlands rise gradually like a saucer to higher land on the East and West. In Kentucky and Tennessee low plateaus change gradually from the Appalachian pla­teau, the western part of the Appalachian Highlands, into the lower lands. The landscape in this central part of the USA is surprisingly flat. Fields of corn and grain can be seen stretching as far as the horizon. It is the richest agricultural area. Originally most of the Central Low­land was covered with forest. The area was supplied with coal and petroleum beneath the trees. The vast area of Lowland is broken by a few masses of hills.

To the South of the Central Lowland, bordering the Coastal Plain, lies the Ozark Plateau. It occupies Southern Missouri and Northern Arkansas and is about 130,000 sq. km. The Ozark Plateau is heavily forested highlands. It is a sparsely populated area. Springfield is one of the few urban centres, and most populated and developed. The soil of the region is poor and only in a few places corn, wheat, and fruit can be raised. Zinc and lead are found in the area. The Ozark Plateau is the only mountainous area between the Appalachians and the Rockies. The highest elevation is about 700 m. In the North, in Wisconsin and Min­nesota, lie the flat-lying rocks, known as the Superior Upland.

The largest part of the Central Lowland is drained by the Missis­sippi and its tributaries the Ohio and the Missouri.

To the west of the Central Lowland are the Great Plains. The name refers both to landform and the extensive short grass prairie, which confronted early explorers. The Great Plains stretch along the eastern edge of the Rockies and their width varies from 480 km in the South to 800 km in the North. Elevations vary from 600 m above sea level in the east to 1,500 m closer to the Rockies.

Most of the Great Plains is a plateau covered with short grass prairies. The eastern edge of the Great Plains is marked by a steep step down to the lower area of the Central Lowland. In the north The Black Hills rise abruptly above surrounding plains. They are a small group of mountains situated in the west of South Dakota. The highest eleva­tion — Harney Peak — is 2,207 m. They derive their name from the dark pines covering the mountains. Wind Cave National Park and Mount Rushmore National Memorial are situated there. Mount Rushmore shows carved faces of four American Presidents: George Washington, Tho­mas Jefferson, Abraham Lincoln, and Theodore Roosevelt. A huge sculp­ture of Chief Crazy Horse, a famous leader of the Sioux has been cut into a mountain near Custer. The mountains are rich in gold. The Home- stake Gold Mine is another tourist attraction. Wild buffalo wander in the area.

The Great Plains depend for most of the precipitation on the Gulf Stream and the amount of precipitation decreases from south-east to north-west. The Great Plains experience the extremes of temperature. The northern plains record the lowest winter temperature. In summer the temperature can go up over 40° C. Agriculture is limited by low rainfall. Cattle-raising predominates. Dry farming is used to raise wheat and other crops. The Great Plains area is rich in minerals: sand, ce­ment, clay, salt, coal, oil and gas.

The Rocky Mountains are the backbone of the Continent. They rise sharply from the Great Plains and stretch from mountainous Alas­ka to New Mexico, presenting a high discontinuous chain of moun­tains. The Rockies form the most important water shed on the conti­nent — the Great or Continental Divide. East of the Divide rivers flow into the Gulf of Mexico, west of it — into the Pacific Ocean. Four largest rivers rise in the Rocky Mountains: the Missouri, the Rio Grande, the Colorado, and the Columbia. The Rocky Mountains are twice as high as the Appalachians. The highest peak is Mount Elbert — 4,399 m. Forty-five other peaks come close to the altitude. The Rockies fall into three parts. The Northern Rockies lie in Montana and Idaho. The Middle Rockies are in Wyoming. The Wyoming Basin, a continuation of the Great Plains, separates the Middle Rockies from the South. The easiest possible way through the mountains is here. Yellow-stone National Park is situated in this part of the Rockies. It is the first National Park of the USA, located in Wyoming and also occupying parts of Idaho and Montana. It is famous for its geysers, bears, buffalo, moose, and coyotes. Geysers and terraced springs add to the attractions of highland country. The South Rockies occupy Colorado and New Mexico and are the highest of the chain. The mountains have enough precipitation to be forested. The forests are dominated by conifers: pines, firs, spruces. The valleys and basins are treeless. The water from the wooded slopes is used for irrigating the nearby lowlands, it also supplies the needs of such cities as Denver and Salt Lake City. The mountains are rich in copper, lead, zinc, silver and gold.

The Rockies form the eastern border of the vast mountain system of North America, the Cordillera. It accounts for 1/3 of the USA and is no more than part of a very much larger system that belongs to a belt of crustal deformation and extends from Cape Horn along the Andes through Central America to North America. The structure of mountains of this type is complex, it is the result of folding and fault­ing, accompanied by volcanic activity. In the far north it is continued from Alaska and the Kurile Islands to Japan. It is a region of tremendous variety. Between the Rocky mountains and the Pacific Mountain Area lies a thinly populated region of high plateaus and driest lands. The

Mojave Desert and Death Valley as well as the Sonorant Desert are situated in the area.

The Region consists of three parts: The Great Basin, the Colorado plateau, and the Columbia Plateau.

The Great Basin is a vast triangular area occupying greater parts of Nevada, Utah, and California, covering 518,000 sq. km. Its eastern boundary is the Wasatch Range and its western boundary is the Sierra Nevada. It is the area of interior drainage. In Nevada streams never reach the sea, instead they fall into blackish lakes, the best known is Great Salt Lake, or disappear in deserts. The precipitation, as well as the length and size of rivers and lakes that depend on it, vary from season to season.

There are numerous hot springs. The basin is divided into numerous desert areas, separated by mountain ranges. The largest is the Mojave Desert and its notorious part Death Valley in California. Death Valley is a low desert, at some places 86 m below sea level. It is 225 km long and from 6 to 25 km wide. On the west it is bounded by the Panamints. Telescope Peak is 3,365 m high and opens a striking panorama of the area. The climate is arid. Summers are the hottest and driest in the USA. The temperature may rise to 56 ° C. The best period is from November to May. It is a National Monument and attracts a lot of tourists. It was called Death Valley in 1849 by gold rush pioneers when many of them died there.

The Mojave Desert is in the south of the Great Basin. It occupies 39,000 sq. km. lying in California and Nevada. The Desert is an enormous recreation area for the residents of Los Angeles. Elevations vary from 600 to 1500 m. The temperature is moderate in winter and high in summer. The annual rainfall is 130 mm. Low shrubs and cactus grow on the slope.

The minerals found in the Great Basin are copper, gold, silver, iron, salt, and clay. Irrigation agriculture is highly productive. Cattle and sheep are raised there as well. To the south-east of the Great Basin the land rises over to a large plateau drained by the Colorado river and its tributaries. The Colorado plateau is almost equal in area to the British Isles. It is an area of flat-lying rocks. General uplift is from 1,600 to 2,600 m. It is the land of canyons and extinct volcanoes, the land of extremes. Forests alterate with deserts, flat areas contrast with canyons and cliffs. The Grand Canyon in northern Arizona is one of the most famous national monuments. It contrasts with the Painted Desert of Arizona. Iron stained red, orange and yellow rocks against light grey and white layers make a superb mosaic. Petrified tree trunks are found in some of the layers but they look like modern axework. Grand Canyon National Park and several other national monuments as well as a few Indian reservations are situated there. The land is rich in uranium; other min­erals are sparse. Striking scenery makes up for the lack of resources. The climate is subtropical and arid.

The Columbia plateau is in the north of the Great Basin, occupy­ing eastern Washington, Oregon and southern Idaho. The Columbia plateau is a volcanic area made of many flows of lava, one on top of another. The area of 650,000 sq. km. is drained by the Columbia and its tributary the Snake. It is also a land of canyons and Hells Canyon, which is 1.6 km deep, is the rival of Grand Canyon of Colorado land. The Snake river flows through it.

The surface of the plateau includes basins and plains; elevation is not high, 500—1,200 m. The land is poor in minerals or timber but is well supplied with water for electric power and irrigation. The lower plains are well cultivated and produce grains, sugar beets, potatoes, fruits and forage crops. Winters are moist and summers are hot and dry.

In the north and east the Columbia Plateau borders the Rockies, in the south — the Great Basin, in the west it borders the Cascade Mountains. The Cascade Mountains are a continuation of the Sierra Nevada, separated from it by deep valleys. The mountains stretch for 1,100 km through Oregon and Washington into British Columbia. The Cascades lie parallel to the Pacific coast between the Rockies, on the west, and the Coast Ranges. The elevation is from 1,500 to 1,800 miles. High picturesque volcanic parks mark the western edge. Mount Rainer rises to 4,392 m. Mount St. Helens had a major eruption in 1980 fol­lowed by a long period of activity. You can find glaciers and snowfields and marked avalanche paths on the slopes of the Cascade Mountains. The mountains derived their name from the foaming rapids of the Columbia, curbed later on, as well as the floods, by a series of dams and locks. The Columbia, the Klamath, and the Fraser rivers cut through the Cascades. The slopes are rich in forests, such valuable species as Douglas fir, hemlock, cedar are found there. On the east the Cascade Mountains border the Puget Sound Lowland. Puget Sound is a deepwater inlet situated in the north-west of state Washington, with a great number of small islands. It was explored by captain George Vancouver in 1792 and named after his helper Puget. The inlet is navigable for large vessels. The Puget Sound Lowland occupies part of Washington and Oregon. The Willamette River takes the southern part of the Lowland, Oregon. In the northern part of it there are two big urban centres — Seattle and Portland.

South to the Cascade Mountains lies the Sierra Nevada, a moun­tain range in eastern California 25,000 sq. miles in area. The name is Spanish for «snowy saw-toothed range». It has long gradual slopes on the west and steep almost vertical slopes on the east. The peaks increase in altitude southward from 1,900 m to 4,418, Mount Whitney, the highest peak of the USA outside Alaska.

A number of rivers have cut deep picturesque canyons on the west­ern slope. Mountain glaciation played an important role in shaping strik­ing landscapes in the Sierra Nevada full of cliffs, waterfalls, and lakes. Forests of commercial timber grow at elevations of 900—1,200 meters; otherwise the range is bare of vegetation. West slope rivers supply irriga­tion water to farmlands in the Sacramento and San Joaquin valleys.

The western slope witnessed the Gold Rush in the 1850s when a large population was attracted to the foothills. Now mining gold or other metals is of no importance. The largest industry is tourism and there are camping and recreation facilities throughout the mountains. The area comprises several national parks. Sequoia National Park was opened in 1890 on the western slope of the Sierra Nevada to protect the big trees, of which there are hundreds with diameter of more than three meters. Yosemite National Park was created to protect great trees and the Yosemite Valley. The Valley (the Indian name is Ah wahnee — «deep grassy valley») is seven miles long and one mile wide. On either side of it rise splendid granite rocks. Yosemite Falls on the north of the valley are the largest falls in North America as the water drops about 800 meters in three stages.

Between the Sierra Nevada and the Coastal Ranges intervenes the valley, which is about 800 km long. The Valley is drained by the Sacra­mento and the San Joaquin rivers which join and enter the Pacific Ocean through the Golden Gate at San Francisco. The Northern end borders the Klamath Mountains and the Cascades. The Valley is highly cultivated, it is a fruit garden of California. All kinds of vegetables especially sugar beets and beans as well as rice and cotton are grown there.

Along the Pacific coast from Washington to Southern California stretch the Coast Ranges. In Washington they are represented by the Olympic Mountains, rich in evergreen trees. Southward the forest thins out with the exception of redwoods in northern California.

The Coast Ranges consists mainly of sedimentary rocks that have been folded and in some cases faulted. The faults have produced some violent earthquakes in California. The San Andreas Fault which is a crack between the two plates of the Earth's surface forms a line from the north to the south of California and is responsible for the San Fran­cisco earth quake of 1986. It is still moving.

The highest elevation of the range in Mount Linn is 2,464 m. The greater part of the range can be described as rough hill land rather than mountains. The valleys are well cultivated. The climate is nice: long dry summers and mild, moderately rainy winters.

Alaska consists of mountain ranges curving round the Gulf of Alas­ka, extending west to form the Aleutian Islands. The mountain systems extend from the USA through Canada. The Coast Range in Alaska continues the Cascade Mountains. The lower slopes of the range are thickly forested; higher elevations are covered with glaciers. North of the Coast Mountains lies the Alaska Range, which has the highest peak in North America Mount McKinley (6,194 m. high). North of the range is a broad plateau, taking half of the state. The major river Yukon flows through it. It rises in Canada and flows 2,900 km to the Bering Sea. Further north are the Arctic Mountains or the Brooks Range, contin­uation of the Rockies. The elevations are not great; the highest peaks are less than 3,000 m. On the north of it the Arctic Slope, a low coastal plain of true tundra a frozen wasteland, extends to the Arctic Ocean. Oil rich Prudhoe Bay area is situated there.

Hawaii is located near the Centre of the Pacific Ocean. It consists of volcanic islands. Active volcanoes can be found in the south-east.

The USA has an extraordinary network of rivers and lakes, includ­ing some of the largest and most useful in the world. Both East and West have traditionally used lakes and streams for transportation, irri­gation, power generation and as public sewers. Despite great efforts to clean them up most waterways are laden with vast poisonous amounts of industrial, agricultural and human wastes.

Waterways of the country could be divided into two large groups: The Eastern systems and the Pacific system. The natural borderline is the Rockies. All the rivers east of the Rockies flow into the Pacific Ocean. For this reason the crests of the Rocky Mountains are known as the Continental Divide.

The Eastern systems consist of three constituent parts: the Missis­sippi and its tributaries, the Great Lakes and St Lawrence system and eastern rivers along the Atlantic Ocean and the Gulf of Mexico.

The mighty Mississippi is one of the world's greatest continental rivers. Its waters are gathered from two-thirds of the United States and together with the Missouri, its chief tributary, the Mississippi flows some 6,400 kilometres from its northern sources in the Rocky Moun­tains to the Gulf of Mexico which makes it one of the world's longest waterways. The river is no doubt the most important geographical feature in the eastern USA. At one end of the river bears prowl through snow, at the other end alligators lie in the sun. The Missis­sippi has been called «the father of waters». On its journey to the sea the Mississippi travels through several states, with its tributaries the river drains all or part of 31 states. Southward it becomes larger and more powerful though it looks harmless and lazy. People who know the river are not deceived by its appearance for they have had many bitter struggles with its floods. The Mississippi is navigable for great distances and is an important waterway. Its eastern branches, chiefly the Ohio and the Tennessee are also navigable for great distances. From the west, however, many of its numerous Great Plains tributar­ies are too seasonal to be used for shipping. The Missouri, for exam­ple, though longer than the Mississippi itself was essentially without navigation until the mid—20^th century, when a combination of dams, locks and dredgings opened the river to barge traffic. Where the Mis­souri pours into the Mississippi, it colours the river deep brown with small pieces of soil. Farther downstream the principal eastern tribu­tary, the Ohio, joins the Mississippi. Its waters are clear, and here one can see the evidence of the difference between the dry west and rainy east. For kilometres, the waters of the two rivers flow on side by side without mixing. Those from the west are brown with pieces of soil from the areas of sparse vegetation. The waters from the east are clear and blue, coming from hills and valleys where forests and plants keep the soil from being washed away. The other two big western tributaries are the Arkansas and the Red River.

The five great lakes four of which are shared with Canada, — Lake Superior, Lake Michigan, Lake Huron, Lake Eire, and Lake Ontario — constitute the largest freshwater lake group in the world. It is an important mid-continental inland waterway connected to the Mississippi — Ohio viaChicago by canals and the Illinois river.

The Great Lakes along with the St. Lawrence form an important route for ocean shipping to reach inland ports. Together, the US and Canada built and operate the St. Lawrence Seaway. Goods can be trans­ported all the way from the Atlantic Ocean to Minnesota on the western end of Lake Superior — a distance of about 3,862 km. The main barrier to navigation is the rapids of the St. Lawrence. Another barrier to navigation is Niagara Falls which is spectacular and beautiful and has always been popular with thrill-seekers and honeymooners. Of the twelve Midwestern states, six touch on the Great Lakes: Ohio, Indiana, Illi­nois, Michigan, Wisconsin, and Minnesota.

The Great Lakes have always played a major role in the Midwest's economy. A number of largest American cities have developed there, Cleveland, Detroit, Chicago, Buffalo. The lakes are used for trans­porting grain, timber, ore, and other products.

The third group of eastern rivers drains the coastal strip along the Atlantic Ocean and the Gulf of Mexico. Except for the Rio Grande, which rises west of the Rockies and flows 3,200 km to the Gulf, few of these rivers are more than 482 km and most of them flow in an almost straight line to the sea. Except in glaciated New England and in arid south-western Texas, most of the larger coastal streams are navigable for some distance, for example the Hudson, the Delaware, and the Everglades in Florida. The water in the Everglades moves very little. It is a wetland area of many small rivers flowing south. A lot of rain falls here each year. There is a great number of low grassy islands between the narrow waterways.

The Rio Grande is the main river of the south-west. It forms a natural boundary between Mexico and the US, which together have built irrigation and flood projects.

The Pacific system comprises the Colorado, the Columbia, the Sacramento, and the San Joaquin rivers.

The Columbia rises in Canada and drains the north. Its length is 1,947 km. Its biggest tributary that flows through a canyon, the Snake, is 1,609 km long. Nearly all of the rivers here are strongly influenced by aridity. In the deserts and steppes they disappear into interior basins. Only one of them, the Great Salt Lake holds some substantial volume of water. The percentage of salt there exceeds that of the ocean. Such lakes have little or no outflow. The lake serves a natural evaporating pan with deposits of salt.

The Columbia river was wild, cutting and shaping the land. Now it flows with quiet dignity. The once wild Columbia has been turned into a stairway of placid lakes whose waters irrigate the arid plateaus of eastern Washington and give power to one of the world's largest hy­droelectric networks.

The Sacramento and the San Joaquin drain the Central Valley of California. The Sacramento rises near Mount Shasta in the southern Cascades and flows southward for 512 km. San Joaquin rises in the Sierra Nevada and drains the lower part of the Central Valley. The two rivers join not far from San Francisco and empty into Suisin Bay, an arm of San Francisco Bay. A number of dams were built on the Sacra­mento to store water and provide flood control. The two rivers supply the cities of California with fresh water, and are also used for irrigation of farmlands and hydroelectric power.

Freshwater lakes are rare in this region especially in California. Lake Tahoe is situated in the Sierra Nevada; Lake Clear is in the Coast Ranges. The largest lake in California is the blackish Salton Sea. It is 48 km long and 16 km wide. It is 72 m below sea level and has no outlet. It was formed from a salt covered depression.

The Colorado River rises in the Front Range of the Rocky Moun­tains. It is 2,740 km long. The Colorado drains the states of Colorado, Utah, Arizona, flows though Marble Gorge and turning west forms deep canyons, the biggest of which is the Grand Canyon. The river is navigable for 230 km up from the estuary. A large territory depends on the river for irrigation and hydroelectric power.

The climate of the United States is extremely varied from arctic in Alaska to subtropical in Florida, and in some ways hostile. One thing that people tend to forget is how far south even the northern parts of the United States are in comparison with Western Europe. New York is on about the same latitude as Naples in Italy. Boston and Detroit are no further north than Rome. In all of the heavily populated parts of the US the summer can be exceedingly hot, and particularly near the eastern seaboard it is very unpleasant. In large cities tremendous heat is built up and made more disagreeable by high humidity. Heat and humidity are naturally most oppressive in the South, but there is not much comfort in the more northern latitudes either. In Texas, the temperature on a typical July day reaches 34° С with relative humidity, but Minneapolis, which is more than 1,609 km north, is only slightly cooler and less humid.

Since the Gulf air is unstable as well as wet, thunderstorms often occur east of the Rockies. They account for a majority of total sum­mer rain. These storms often come as short-lived, sometimes violent downpours. Relief from the humid heat comes in the northern Midwest (from occasional outbursts of cool Canadian air) and at high eleva­tions in the Appalachians, as well as in the area of the Great Lakes. East of the Rockies, however, US summers are distinctly uncomfortable, and only air conditioning makes summer life tolerable.

Again the Pacific area is different. The subtropical but cool waters of the Pacific bring mild and stable air. Except in the mountains the Pacific Coast is nearly rainless though often foggy. Temperatures are very high (40—500 C). Texas (on the east) and Idaho (on the north) are turned into a summer desert.

In winter, on the other hand, it can be very cold. Particularly away from the coast the winter cold is so intense that strong heating systems are essential if normal life is to be carried on. Even near the east coast in New York and Boston there are some spells of very cold weather, though they can turn to much milder weather. Weather changeability is remarkable. Within a short period of time people must adapt themselves from almost arctic conditions to a few days of warm sunshine, then colder weather. Winter temperatures differ widely, (from +13°C to —18 °C) depending largely on latitude. But the main uniformity of Eastern weather in wintertime is the expectation of fre­quent change.

Winter climate on the West Coast is very different. Relatively warm, moist air spreads south from the Aleutian Islands in Alaska and brings mists, drizzles, and rains. Southern California receives nearly all of its rain at this time of year. The Pacific air brings mild temperatures along the length of the coast. The temperature on a January day in Seattle (Washington) can vary from +1 °C to +7 °C. In southern California, however, rains are separated by long spells of fair weather. One of the greatest advantages of California is the fact that there are no extremes in temperature. Except in the desert the summer is never intolerably hot, and the winter is mild

Over most of the United States, as in most continental climates, spring and autumn are agreeable but disappointingly brief. Autumn is particularly idyllic in the East, with a romantic Indian summer. It is the period of mild days and frosty nights. But along the Atlantic and Gulf coasts autumn is the season for hurricanes — the American equivalent of typhoons of the Asian Pacific. Originating in the Caribbean those circular storms tend to move north-eastwards, and any part of the deep South is liable to find itself in the track of a particular hurricane. In general it is the areas nearest to the coasts, which suffer most severely.

Another problem of the eastern half of the United States behind the Appalachian Mountains, in the whole basin of the Mississippi, is the danger of flooding. Severe storms and heavy rainfalls can raise the level of the river and its tributaries to dangerous heights. In the history of the US riverfloods have probably caused more damage than any other single climatic element.

Дата добавления: 2013-12-13