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North America,third largest continent (1990 est. pop. 365,000,000), c.9,400,000 sq mi (24,346,000 sq km), the northern of the two continents of the Western Hemisphere. North America includes all of the mainland and related offshore islands lying N of the Isthmus of Panama (which connects it with South America). The term "Anglo-America" is frequently used in reference to CanadaCanada
, independent nation (2001 pop. 30,007,094), 3,851,787 sq mi (9,976,128 sq km), N North America. Canada occupies all of North America N of the United States (and E of Alaska) except for Greenland and the French islands of St. Pierre and Miquelon.
..... Click the link for more information. and the United StatesUnited States,
officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and in area. It consists of 50 states and a federal district.
..... Click the link for more information. combined, while the term "Middle America" is used to describe the region including MexicoMexico
, Span. México or Méjico , officially United Mexican States, republic (2005 est. pop. 106,203,000), 753,665 sq mi (1,952,500 sq km), S North America.
..... Click the link for more information. , the republics of Central America, and the Caribbean.
Geology and Geography
The continent is bounded on the north by the Arctic Ocean, on the west by the Pacific Ocean and the Bering Sea, and on the east by the Atlantic Ocean and the Gulf of Mexico. Its coastline is long and irregular. With the exception of the Gulf of Mexico, Hudson Bay is by far the largest body of water indenting the continent; others include the Gulf of St. Lawrence and the Gulf of California (Sea of Cortès). There are numerous islands off the continent's coasts; Greenland and the Arctic Archipelago, the Greater and Lesser Antilles, the Alexander Archipelago, and the Aleutian Islands are the principal groups. Denali (Mt. McKinley; 20,310 ft/6,190 m), Alaska, is the highest point on the continent; the lowest point (282 ft/86 m below sea level) is in Death Valley, Calif.
The Missouri-Mississippi river system (c.3,740 mi/6,020 km long) is the longest of North America. Together with the Ohio River and numerous other tributaries, it drains most of S central North America and forms the world's greatest inland waterway system. Other major rivers include the Colorado, Columbia, Delaware, Mackenzie, Nelson, Rio Grande, St. Lawrence, Susquehanna, and Yukon. Lake Superior (31,820 sq mi/82,414 sq km), the westernmost of the Great LakesGreat Lakes,
group of five freshwater lakes, central North America, creating a natural border between the United States and Canada and forming the largest body of freshwater in the world, with a combined surface area of c.95,000 sq mi (246,050 sq km).
..... Click the link for more information. , is the continent's largest lake. The Saint Lawrence SeawaySaint Lawrence Seaway,
international waterway, 2,342 mi (3,769 km) long, consisting of a system of canals, dams, and locks in the St. Lawrence River and connecting channels between the Great Lakes; opened 1959.
..... Click the link for more information. , which utilizes the St. Lawrence River and the Great Lakes, enables oceangoing vessels to penetrate into the heart of North America.
Physiographically, the Anglo-American section of the continent may be divided into five major regions: the Canadian ShieldCanadian Shield
or Laurentian Plateau
, U-shaped region of ancient rock, the nucleus of North America, stretching N from the Great Lakes to the Arctic Ocean. Covering more than half of Canada, it also includes most of Greenland and extends into the United States as the
..... Click the link for more information. , a geologically stable area of ancient rock that occupies most of the northeastern quadrant, including Greenland; the Appalachian MountainsAppalachian Mountains
, mountain system of E North America, extending in a broad belt c.1,600 mi (2,570 km) SW from the Gaspé Peninsula in Quebec prov., Canada, to the Gulf coastal plain in Alabama. Main sections in the system are the White Mts., Green Mts.
..... Click the link for more information. , a geologically old and eroded system that extends from the Gaspé Peninsula to Alabama; the Atlantic-Gulf Coastal Plain, a belt of lowlands widening to the south that extends from S New England to Mexico; the Interior Lowlands, which extend down the middle of the continent from the Mackenzie valley to the Gulf Coastal Plain and includes the Great Plains on the west and the agriculturally productive Interior Plains on the east; and the North American Cordillera, a complex belt of geologically young mountains and associated plateaus and basins, which extend from Alaska into Mexico and include two orogenic belts—the Pacific MarginPacific Margin,
western section of the great North American Cordillera, W United States and W Canada, stretching from SW Alaska to S Calif. It is composed of a central lowland region (Central Valley, Willamette valley, Puget Sound lowlands) flanked by the Coast Ranges on the
..... Click the link for more information. on the west and the Rocky MountainsRocky Mountains,
major mountain system of W North America and easternmost belt of the North American cordillera, extending more than 3,000 mi (4,800 km) from central N.Mex. to NW Alaska; Mt. Elbert (14,431 ft/4,399 m) in Colorado is the highest peak.
..... Click the link for more information. on the east—separated by a system of intermontane plateaus and basins. The Coastal Plain and the main belts of the North American Cordillera continue south into Mexico (where the Mexican Plateau, bordered by the Sierra Madre Oriental and the Sierra Madre Occidental, is considered a continuation of the intermontane system) to join the Transverse Volcanic Range, a zone of high and active volcanic peaks S of Mexico City.
During the Ice Age of the late Cenozoic era, a continental ice sheet, centered west of Hudson Bay (the floor of which is slowly rebounding after being depressed by the great weight of the ice), covered most of N North America; glaciers descended the slopes of the Rocky Mts. and those of the Pacific Margin. Extensive glacial lakes, such as Bonneville (see under Bonneville Salt FlatsBonneville Salt Flats
, desert area in Tooele co., NW Utah, c.14 mi (22.5 km) long and 7 mi (11.2 km) wide. The smooth salt surface of the Flats is ideal for auto racing, and several world land speed records have been set there.
..... Click the link for more information. ), LahontanLahontan, Lake
, extinct lake of W Nev. and NE Calif. It was formed by heavy precipitation caused by the Pleistocene glaciers and with Lake Bonneville (see under Bonneville Salt Flats) occupied a part of the Great Basin region.
..... Click the link for more information. , AgassizAgassiz, Lake
, glacial lake of the Pleistocene epoch, c.700 mi (1,130 km) long, 250 mi (400 km) wide, formed by the melting of the continental ice sheet beginning some 14,000 years ago; it eventually covered much of present-day NW Minnesota, NE North Dakota, S Manitoba, central
..... Click the link for more information. , and Algonquin, were formed by glacial meltwater; their remnants are still visible in the Great BasinGreat Basin,
semiarid, N section of the Basin and Range province, the intermontane plateau region of W United States and N Mexico. Lying mostly in Nevada and extending into California, Oregon, Idaho, and Utah, it is bordered by the Sierra Nevada on the west, the Columbia Plateau
..... Click the link for more information. and along the edge of the Canadian Shield in the form of the Great Salt LakeGreat Salt Lake,
shallow body of saltwater, NW Utah, between the Wasatch Range on the east and the Great Salt Lake Desert on the west; largest salt lake in North America.
..... Click the link for more information. , the Great Lakes, and the large lakes of W central Canada.
North America, extending to within 10° of latitude of both the equator and the North Pole, embraces every climatic zone, from tropical rain forest and savanna on the lowlands of Central America to areas of permanent ice cap in central Greenland. Subarctic and tundra climates prevail in N Canada and N Alaska, and desert and semiarid conditions are found in interior regions cut off by high mountains from rain-bearing westerly winds. However, a high proportion of the continent has temperate climates very favorable to settlement and agriculture.
The first human inhabitants of North America are believed to be of Asian origin; they crossed over to Alaska from NE Asia roughly 20,000 years ago, and then moved southward through the Mackenzie River valley. European discovery and settlement of North America dates from the 10th cent., when Norsemen settled (986) in Greenland. Although evidence is fragmentary, they probably reached E Canada c.1000 at the latest. Of greater impact on the subsequent history of the continent were Christopher Columbus's exploration of the Bahamas in 1492 and later landings in the West Indies and Central America, and John Cabot's explorations of E Canada (1497), which established English claims to the continent. Spanish and French expeditions also explored much of North America.
Although the population of Canada and the United States is still largely of European origin, it is growing increasingly diverse with substantial immigration from Asia, Latin America, and Africa; it is also highly urbanized (about 74% live in urban areas); much of the population is centered in large conurbations and coalescing urban belts along the southern margin of Canada and in the northeastern quadrant of the United States around the Great Lakes and along the Atlantic coast. Mexico's population, about 60% mestizo (of European and Native American descent), is increasingly urbanized (about 72%). People of European descent are a minority in most Central American and Caribbean countries, and the population outside the major cities is largely rural. The largest urban agglomerations on the continent are Mexico City, New York City, Los Angeles, and Chicago.
Resources and Economy
North America's extensive agricultural lands (especially in Canada and the United States) are a result of the interrelationship of favorable climatic conditions, fertile soils, and technology. Irrigation has turned certain arid and semiarid regions into productive oases. North America produces most of the world's corn, meat, cotton, soybeans, tobacco, and wheat, along with a variety of other food and industrial raw material crops. Mineral resources are also abundant; the large variety includes coal, iron ore, bauxite, copper, natural gas, petroleum, mercury, nickel, potash, and silver. The manufacturing that provided a high standard of living for the people of Canada and the United States has significantly declined, and formerly abundant factory jobs are increasingly replaced by those in the service sector. Much of this manufacturing has moved to Mexico (especially in the border zone adjoining the United States), which offers a large and inexpensive labor force.
See T. H. Clark and C. W. Stearn, The Geological Evolution of North America (1968); W. P. Cumming et al., The Discovery of North America (1972); R. C. West et al., Middle America: Its Lands and Peoples (3d ed. 1989); T. L. McKnight, Regional Geography of the United States and Canada (1992); S. Birdsall, Regional Landscapes of the United States and Canada (4th rev. ed. 1992); T. Flannery, The Eternal Frontier: An Ecological History of North America and Its Peoples (2001); A. Taylor, American Colonies (2001).
North America is a continent in the western hemisphere. Its extreme points are Cape Murchison in the north (71 °50’ N lat.), Cape Prince of Wales in the west (168° W long.), and Cape Saint Charles in the east (55°40’ W long.). In the south it is connected with South America, the boundary running through the Isthmus of Panama. Central America is usually classified with North America. The continent has an area of 20,360,000 sq km (24,250,000 sq km with its islands). The largest islands are Greenland, the Canadian Arctic Archipelago, the West Indies, and the islands along the west coast of the continent, including the Aleutians, the Alexander Archipelago, the Queen Charlotte Islands, and Vancouver Island. North America is bounded by the Arctic Ocean on the north, with Hudson Bay cutting deeply into the mainland, by the Atlantic Ocean and Gulf of Mexico on the east and southeast, and by the Pacific Ocean and Gulf of California on the west. The major peninsulas are Boothia and Melville in the north, Labrador, Florida, and Yucatán in the east, and Lower (Baja) California and the Alaska and Seward peninsulas in the west.
North America has a highly diverse shoreline. The most indented coasts are found in mountain regions that have experienced glaciation: Greenland, the eastern part of the Canadian Arctic Archipelago, and the Pacific coast of Canada and southern Alaska. These glacial-tectonic and glacial-erosion coasts are intricate systems of fjords. Whereas the Gulf of Saint Lawrence has both straight abrasion and bay shores, the peninsulas of Nova Scotia and the northeastern USA have tectonic and erosion-tectonic coastlines with numerous skerries. South of 43° N lat., the Atlantic coast, is an accumulative lagoon coast complicated by estuaries and deltas. Between 37° and 40° N lat. the estuaries are especially large. In southern Florida and parts of Central America the coast is formed of coral reefs and mangrove swamps. With the exception of its northern part, the Pacific coast is less indented, especially from Lower (Baja) California to the US-Canadian border, where an abrasion-bay shoreline predominates. Western Canada and southern Alaska have a fjord coastline. Accumulative bay, delta, and thermal-abrasion shores are typical of the western and northern coasts of Alaska.
Orography. The surface of the continent has an asymmetrical structure, with the Cordilleras occupying the western part and vast plains and low mountains the eastern part. The average elevation drops from about 1,700 m in the west to roughly 200–300 m in the east. The overall average elevation of North America is 720 m.
The extensive development of platform structures promoted the formation of large plateaus and plains in the central and eastern parts of the continent. In the north and northeast, chiefly in Canada, lies the Laurentian Upland, a plateau region. To the south, largely in the USA, stretch the Central Plains, gradually merging in the west with the higher Great Plains (500–1,500 m), a vast piedmont belt of the Cordilleras. North of the Great Plains is the Mackenzie Lowland. The Central Plains are bounded on the east by the Appalachian Mountains, which extend from southwest to northeast as far as Newfoundland.
Mountain topography is typical for the eastern parts of the Canadian Arctic Archipelago and the coast of Greenland. Together with favorable climatic conditions, this terrain promotes the formation of enormous glaciers in the northern part of the continent, including most of Greenland and a large part of the Canadian Arctic Archipelago. To the west the mountains gradually become lower and are replaced by the plateaus and lowlands that are characteristic of the western islands of the archipelago. Coastal lowlands, including the Atlantic Lowlands in the east and the Mexican Lowlands in the south, form the southeastern edge of the continent.
The Cordilleras include a number of mountain arcs with a predominantly northwest to southeast orientation. The eastern arc consists of the Brooks Range, the Mackenzie Mountains, the Rocky Mountains (Mount Elbert, 4,399 m), and the Sierra Madre Oriental. To the west stretches an irregular belt of interior uplands and plateaus with elevations of 1,000 m to 2,000 m: the Yukon Plateau, the volcanic British Columbia plateaus, the Columbia Plateau, the Great Basin, the Colorado Plateau, and the volcanic plateaus and uplands of the interior of the Mexican Highlands. Most of the plateaus consist of a succession of flat tablelands, mountain ranges, and basins (Death Valley in the Great Basin lies 85 m below sea level).
On the west the belt of plateaus and uplands is bounded by the highest mountain ranges in the Cordilleras. This mountain system includes the volcanic Aleutian Islands, the Aleutian Range, the Alaska Range, whose highest peak is Mount McKinley (6,193 m), the highest point in North America, the Canadian Coast Mountains, the Cascade Range, the Sierra Nevada, the Sierra Madre Occidental, and the Transverse Volcanic Sierra with the volcano Orizaba (5,700 m). To the west of this mountain system lies a zone of depressions occupied by bays (Cook Inlet, Puget Sound, and the Gulf of California) or by lowlands (Willamette Valley, Central Valley). The west coast of the continent is formed by the Kenai, Chugach, St. Elias (Mount Logan, 6,050 m), and Canadian island mountains and the US Coast Ranges. South of the Mexican Highlands the Cordilleras divide into two chains. One chain is deflected to the east, forming the underwater ridges and islands of the West Indies and then joining the Andes of Venezuela; the other extends through the Isthmuses of Tehuantepee and Panama to the Colombian Andes.
Origin and development of the topography. The variations in the topography are related to the differences in the age of present-day land regions and to the history of the continental development of these regions. The topography of the Laurentian Upland, which has the most ancient geological structures, is characterized by planation surfaces formed in the Early Paleozoic. The varying resistance of rocks to denudation, as well as tectonic movments, produced the rolling surface of the upland. Quaternary glaciation caused the central part of the upland to subside, forming the basin of Hudson Bay, and led to the accumulation of moraine and fluvioglacial detritus, which formed the moraine-hilly topography.
The Central and Great Plains are stratified plains. Through the action of denudation processes, depending on the type of rock bedding, there arose cuesta ridges (in the Great Lakes region), stepped plateaus (Great Plains), and low- and medium-elevation erosion mountains (Ozarks and Ouachitas). In the north as far as 42° N lat., where the plains were subjected to continental glaciation, they have a hilly moraine topography. The central parts of the plains are deeply dissected by rivers and gulleys, and south of 38° N lat. the plains reflect karst processes.
The coastal lowlands, formed by the gradual retreat of the ocean in Mesozoic and Cenozoic times, have preserved young forms of marine accumulative topography on their outer edge (terraces, spits, and bars). The older interior parts of the coastal lowlands have a structural-erosion topography—low plateaus separated by cuesta scarps. The topography of the Appalachian Mountains was created as rivers eroded the rising structures; the northern Appalachians, which underwent glaciation, typically have such glacial forms as broad U-shaped valleys and moraine deposits in intermontane depressions.
The formation of the mountains on the arctic islands is related to crustal movements in the Mesozoic and Cenozoic, which simultaneously created the large basins on the floor of the northern Atlantic and the Arctic Ocean. The extrusions of basalt that accompanied these movements created the highlands in eastern Greenland. Ancient and modern glaciation determined the exceptionally rugged topography, marked by numerous cirques, trough valleys, and fjords. The central and western parts of the Canadian Arctic Archipelago consist of stepped plateaus and marine accumulative lowlands with ther-mokarst lakes and other permafrost landforms.
The Cordilleras are a belt of active relief formation, primarily on the young Mesozoic and Cenozoic folded structures and the adjacent activated segments of the North American Platform. The eastern arc of the Cordilleras has three types of ranges. The first type, block-folded ranges, arose as a result of vast arched uplifts and subsequent erosion dissection. They include the Brooks Range, the Mackenzie Mountains, the eastern ranges of the Rockies in Canada and the northern USA, and the Sierra Madre Oriental. The mountains reach elevations of 3,000–3,900 m and are separated by deep longitudinal valleys. North of 40° N lat. mountain glacial forms are widespread, and south of that point nival and erosion forms predominate. Ranges of the second type, folded-block and anticlinal ranges, are found in the southern part of the American Rockies. They were formed through the deformation of the edge of the North American Platform and are separated by vast synclinal troughs. Ranges of the third type, block and folded-block mountains and massifs, occur in the batholith regions in the western part of the Rocky Mountains and have alpine forms.
The system of inner plateaus and uplands consists for the most part of denudation plateaus. In the northern part of the system (Alaska and northwestern Canada), large and relatively high massifs with a flat or rolling surface alternate with broad accumulative basins connected by river valleys. In the southern USA and Mexico, in regions with a dry continental climate, such as the Great Basin and the northern Mexican Highlands, the plateaus consist of many strongly denuded crests and broad depressions filled with alluvial-deluvial deposits. Lava plateaus with flat surfaces and deeply dissected canyons occupy large areas along the US-Canadian border and in the southern Mexican Highlands. They include the Fraser and Columbia plateaus and the Meseta Central. In the southern part of the Columbia Plateau and along the southern margin of the Mexican Highlands fault movements and volcanic activity (in Mexico) have created a mountainous terrain. The Colorado Plateau, tectoni-cally a fragment of the North American Platform that became part of the Cordilleras, also belongs to the inner belt of plateaus.
The western belt of the Cordilleras includes two mountain systems, corresponding to major geoanticlines, and the system of basins (synclinoria) that divides them. The eastern system, the higher one, consists of block mountains formed on Nevadan batholith with steep, often asymmetrical slopes and crestlike summits (Canadian Coast Mountains and Sierra Nevada). Other ranges (Alaska, St. Elias) are large anticlinal folds with instrusive outcrops along their axes. The relief of these mountains is predominantly alpine, and north of 60° N lat. they are covered by large glaciers. This arc also includes volcanic mountains—the Aleutian Range, Wrangell Mountains, Cascade Range, and Transverse Volcanic Sierra—all of them formed by recent eruptions and constituting rows of volcanic cones rising above a common base. Many of the volcanoes, notably Mount Wrangell, Lassen Peak, and Popocatépetl, are active. The west coast of the continent and the coastal islands in southern Alaska and western Canada are formed by narrow anticlinal ranges of recent origin.
G. M. IGNATEV
Geological structure and minerals. The large central part of North America is occupied by the Precambrian North American (Canadian) Platform, which also includes all but the northern and northeastern edge of Greenland. The platform is surrounded by Caledonian folded mountain structures (northeastern part of the mainland, Greenland, Newfoundland, and the northern Appalachians), by Hercynian folded structures (southern Appalachians, Ouachita Range and its buried continuation, and the Canadian Arctic Archipelago), and by the Mesozoic and Cenozoic Cordilleras. The lowlands along the Atlantic and Gulf of Mexico in the USA, covered by a mantle of Mesozoic and Cenozoic deposits, are continental platform segments with a Paleozoic and, to some extent, Precambrian, basement.
The basement of the North American Platform is exposed in the northern USA, Canada, the southern part of the Canadian Arctic Archipelago, and along the western and southeastern coasts of Greenland, forming the Canadian (Canadian-Greenland) Shield. The shield consists of blocks (provinces) bounded by faults and composed of metamorphosed, chiefly basic, volcanic rocks and granite gneisses of Archean and Early Protero-zoic age. In the southeastern part of the shield stretches the Grenville Belt, consisting of Early Precambrian rock reworked in the Late Proterozoic and of metamorphosed Proterozoic carbonate detrital formations enclosing masses of granite and gab-bro-anorthosite. According to data obtained from drilling and geophysical studies, the basement of the remainder of the platform, covered by a sedimentary mantle, is also composed primarily of Early Precambrian metamorphosed sedimentary and volcanic rocks and granite gneisses. Early Precambrian crystalline rocks are also found in the American Rockies.
The sedimentary mantle of the North American Platform forms the continental platform segments of the mid-continent and Great Plains. The mantle of the mid-continent ranges in age from Ordovician to Carboniferous; Permian rocks are found in the east. The mantle of the Great Plains also includes deposits from the Mesozoic and continental Cenozoic. Variations in the depth of the basement have produced a series of major depressions (syneclises) descending to 3–4 km and arches (anteclises). The southwestern part of the platform is dissected by the mobile zone of the northwesterly Ouachita Mountains.
The most ancient part of the folded border of the North American Platform, the Caledonian mountains of northeastern Greenland, is composed of a thick layer of sedimentary terrigenous-carbonate rocks of the Upper Precambrian and Lower Paleozoic, intensively deformed before the Devonian together with the ancient Precambrian basement and thrust onto the margin of the platform as nappes. Coarse red Devonian deposits, the products of destruction in Caledonian mountain building, fill the grabens superimposed on the platform margin; the grabens also contain younger sediments from the Upper Paleozoic and Mesozoic.
In the southeast the margin of the platform is bounded by the Paleozoic (Caledonian in the north and Hercynian in the south) folded system of the Appalachians and Newfoundland. The northern Appalachians and the folded system of Newfoundland border on the Canadian Shield along a fault (the Logan line) where Paleozoic geosynclinal strata are thrust onto the Paleozoic and Precambrian platform. In the central zone of the northern Appalachians there are superimposed basins filled with weakly deformed, primarily continental. Carboniferous and Permian deposits. Both the northern and southern Appalachians have narrow grabens with continental sediments and basalt lavas of the Upper Triassic and Lower Jurassic created by the break-up of the Appalachian system before it entered the platform stage of development.
Along the Atlantic and Gulf of Mexico, within the coastal lowlands, the zone of Hercynian folding is covered by a layer of Cretaceous and Cenozoic deposits. The Hercynian (Innuitian) folded system of the Canadian Arctic Archipelago and northern parts of Greenland is composed primarily of terrigenous carbonate Cambrian-Devonian beds that were folded in the early Carboniferous. Near Sverdrup Island and the adjacent islands, the large and deep Sverdrup Basin, filled with terrigenous platform deposits of the Upper Paleozoic and Mesozoic, is superimposed on the folded Paleozoic basement. The deposits are breached by salt domes (Upper Paleozoic) associated with gas deposits.
The Cordilleran folded belt stretches along the Pacific coast of North America. In the east, the folded belt almost everywhere borders on the North American Platform; only in Alaska is it bounded by the Brooks Range, part of the Innuitian Belt. In the south the Cordilleras merge with the structures of the Antilles-Caribbean region. Within the Cordilleran belt there is an eastern miogeosynclinal zone and a western eugeosynclinal zone. The miogeosyncline’and eastern part of the eugeosyn-cline were formed in the Late Precambrian and Early Paleozoic, and the western part of the eugeosyncline was created in the Mesozoic. Stretching along the western margin of the platform, the miogeosyncline includes the western zone of the Rocky Mountains, whose eastern part in the USA is the uplifted activated periphery of the North American Platform.
The eugeosyncline of the Cordilleras may be traced from the Alaska Peninsula to the Isthmus of Panama and on into the northern Andes. In the eastern part of the eugeosyncline (the Alaska Range, Canadian Coast Mountains, and Sierra Nevada), the geosynclinal complex of rocks, dating from the Cambrian to the Jurassic, includes cherts, basic and neutral volcanic rocks, and terrigenous rocks. The rocks are connected by complex facies transitions about 10 km thick. The most intensive (Nevadan) folding in the eugeosyncline, which produced the intricate folded-sheet structure of the belt, occurred in the Late Jurassic. The largest granite masses—the Canadian Coast Batholith and the Idaho, Sierra Nevada, and California batholiths—were formed between the Late Jurassic and Paleo-gene.
The western part of the eugeosyncline, which runs along the Pacific coast of Alaska, Vancouver Island, and the Queen Charlotte Islands, through Oregon, California, and Mexico, and on to Central America, is composed of formations of Late Jurassic to Miocene age. The lower part of the cross section is dominated by deep-water detrital series alternating with interlayers of basalts, keratophyres, and cherts. Paleogene and Neogene beds are represented by a flysch complex with pockets of volcanic rocks and jaspers. In Alaska and in the Cascade Range the cross section is topped by andesites, and on the Columbia Plateau by plateau basalts. The total thickness exceeds 10 km. Fold-forming movements occurred numerous times. The development of large thrust faults oriented west and of such slip-strike faults as the San Andreas Fault is related to them. The principal epoch of folding and thrust-fault formation in the western part of the eugeosyncline was the Late Miocene. A belt of ophiolites was formed in Alaska, in the Coast Ranges of California, and in Central America during the Mesozoic (Jurassic).
MINERALS. Most of the deposits of useful minerals in North America are confined to the Canadian Shield and the Cordilleras. The Precambrian rocks of the Canadian Shield contain major deposits of iron ore (around Lake Superior and on the Labrador Peninsula), sulfide, copper, nickel, and uranium ores (north shore of Lake Huron), gold (the Porcupine region), and nonferrous metals. The platform’s sedimentary mantle, primarily at the boundary with folded regions, contains many deposits of petroleum and gas in all the Paleozoic systems (in the west, in the Mesozoic systems as well). The largest coal reserves occur in the eastern and western interior coal basins of the North American Platform.
In the Cordilleras there are many known deposits, in some places quite large, of gold, silver, copper, zinc, lead (Pine Point), molybdenum, tungsten, and mercury; iron ore is less widespread. Significant petroleum and gas deposits are found along the Pacific Coast, in California and southern Alaska (Cook Inlet), in the foothills of the Canadian Rockies, and in the eastern part of the American Rockies. Coal deposits occur in the Cretaceous beds of the Rocky Mountains and in the interior basins of the Canadian Cordilleras. Sedimentary uranium ores are found in the Lower Mesozoic formations of the Rocky Mountains, and the Paleozoic rocks of this region contain stratified beds of phosphorites.
REFERENCESKing, P. B. Geologicheskoe razvitie Severnoi Ameriki. Moscow, 1961. (Translated from English.)
King, P. B. Tektonika Severnoi Ameriki. Moscow, 1972. (Translated from English.)
Douglas, R. Geology and Economic Minerals of Canada. Ottawa, 1970.
V. E. KHAIN and N. A. BOGDANOV
Climate. Much of the area north of 56° N lat. has an annual radiation balance of less than 20 kcal/sq cm, or 84 kj/sq cm (Greenland has a negative balance), but to the south it increases rapidly, reaching 60–80 kcal/sq km, or 250–335 kj/sq cm south of 30° N lat. Over most of the continent the predominant air movement is from west to east; only in the south, in the tropical latitudes, is there a predominant northeast to southwest movement (trade winds). The prevailing westerly transfer of air occurs during cyclonic activity. In the winter this activity, strong over the Pacific Coast, diminishes over the Cordilleras and again intensifies over the interior plains. Anticyclones often develop above the inner plateaus of the Cordilleras. Cold arctic air is carried far to the south in the wake of the cyclones, sometimes reaching the Gulf of Mexico. In the front parts of the cyclones warm moist tropical air often reaches the north, causing a rise in temperature and precipitation, which is especially abundant in the eastern parts of the continent.
As a result of these processes, warm rainy weather with snow in the mountains predominates during the winter on the Pacific coast; most of Alaska, the interior plateaus of the Cordilleras, and northwestern Canada have dry, cold weather; and the central and eastern parts of the continent have unstable weather with freezes and thaws and frequent snowfall. Only in the tropical parts of the southern Mexican Highlands and Florida, which receive the trade winds, are winters warm and relatively dry.
In summer the westerly shift of air weakens. Air from the Gulf of Mexico, moving northeast along the western periphery of the Azores anticyclone, spreads over the continent bringing large amounts of moisture to the central and eastern regions. The equatorial monsoon reaches Central America and the West Indies, causing abundant precipitation. Pacific air moves southward along the eastern periphery of the Hawaiian anticyclone and along the west coast of the continent. The Pacific air usually does not cause summer precipitation, except in southeastern Alaska, where it reaches the coast at an angle. Sometimes the Hawaiian and Azores anticyclones converge, and dry tropical air moves eastward along the northern edge of the crest of high pressure that connects them. In such cases dry, hot weather with strong winds sets in over most of the continent in the south. Dust storms frequently occur in the Great Basin and on the Great Plains at this time. Cool weather prevails in the north during the summer and in the northeastern part of the continent, which is influenced by cold currents.
Tehe mean January temperature ranges from -36°C in the northern part of the Canadian Arctic Archipelago to 20°C in southern Florida and the Mexican Highlands. The lowest temperature, -64°C, was recorded in Alaska and northwestern Canada; on the Greenland ice cap, at an elevation of 3,000 m, the temperature has dropped to - 70°C. Temperatures below 0°C occur everywhere except on the west coast south of 40° N lat., the southern tip of Florida, and the lowlands of southern Mexico and Central America.
Mean July temperatures range from 4°C in the northern part of the Canadian Arctic Archipelago to 32°C in the southwestern USA. The highest temperatures are observed in the southern parts of the Cordilleran interior plateaus; in Death Valley the temperature has reached 57°C, the highest temperature in the western hemisphere.
The greatest amount of precipitation falls in southeastern Alaska, western Canada, and the American Northwest, where it averages 2,000–3,000 mm a year, increasing to 6,000 mm in places, chiefly during the winter and autumn. In the southeastern USA the annual precipitation totals 1,000–1,500 mm, primarily from summer rains. The Central Plains and northeastern part of the continent receive 600–1,000 mm a year, most of it in summer. The Great Plains receive 400–600 mm, and the interior plateaus, less than 100 mm in places. On the west coast, south of 37° N lat., the amount of precipitation drops sharply, primarily as a result of the almost completely dry summer. In Lower (Baja) California the annual precipitation does not exceed 100–150 mm.
During the winter a stable snow cover forms north of 40° N lat. (north of 44° N lat. on the Great Plains). By the end of the winter the snow cover ranges from a few centimeters on the interior plateaus of the Cordilleras to 1 meter or more in the northwestern and northeastern parts of the continent.
North America extends over the arctic, subarctic, temperate, subtropical, tropical, and subequatorial zones.
The arctic zone includes the land bounded by the Arctic Ocean. Greenland and the eastern part of the Canadian Arctic Archipelago have a harsh climate with low summer and winter temperatures and relatively large amounts of precipitation, causing considerable glaciation. The northern coast of Alaska and the western part of the Canadian Archipelago have a more continental arctic climate with little precipitation. The subarctic zone, extending from 58° N lat. in the west and from 50° N lat. in the east, is characterized by abundant precipitation, warm winters, and cool summers in the west along the Pacific. The central part of the subarctic zone, east of the Cordilleras, is markedly continental with very cold weather. The eastern subarctic zone has snowy winters and cold wet summers.
The temperate zone, north of 40° N lat., is distinguished by a mild, very wet climate in the west, a severe continental climate in the interior plateaus of the Cordilleras, and a moderately continental climate in the east. In the subtropical zone (which includes the entire southern USA excluding the southern tip of Florida), the western part of California has a mild Mediterranean
|Table 1. Primary climatic indexes of North America|
|Zone||Point||Latitude (N)||Longitude (W)||Elevation (m)||Mean air temperature (°C)||Precipitation (mm)|
|By months||Annual||By months|
|Barrow||70°23′||156°17′||7||5 (July)||-28 (Feb.)||112||24 (July)||3 (Apr.)|
|Subarctic||Dillingham||59°00′||158°25′||24||13 (July)||-9 (Feb.)||663||100 (Sept.)||33 (Apr.)|
|Fort Smith||60°00′||111°52′||207||16 (July)||-27 (Jan.)||331||55 (July)||2 (Mar.)|
|Hebron||58°12′||62°21′||15||9 (Aug.)||-21 (Jan.)||481||84 (Sept.)||13 (Feb.)|
|Temperate||Prince Rupert||54°18′||130°18′||52||14 (Aug.)||-2 (Jan.)||2,417||311 (Nov.)||103 (July)|
|Winnipeg||49°53′||97°07′||232||19 (July)||-19(Jan.)||547||80 (June)||22 (Feb.)|
|Boston||42°21′||71°04′||38||22 (July)||-2 (Feb.)||1,021||93 (Feb.)||74 (June)|
|Subtropical||San Francisco||37°48′||122°26′||47||12(Sept.-oct.)||7 (Jan.)||562||113 (Jan.)||0(July-Oct.)|
|Winnemucca||40°58′||117°43′||1,324||21 (July)||-2 (Jan.)||216||26 (Jan.)||5(July-Aug.)|
|Kansas City||39°05′||94°37′||294||26 (July)||-2 (Jan.)||941||129 (June)||29 (Jan.)|
|Washington||38°54′||77°03′||34||25 (July)||1 (Jan.)||1,068||118(July)||61(Nov.)|
|Mexico||19°24′||99°11′||2,309||17 (May)||12 (Jan.)||765||163 (July)||6 (Jan.)|
|Miami||25°48′||80°12′||8||28 (Aug.)||20 (Jan.)||1,410||177 (June)||42 (Dec.)|
|Subequatorial||Tapachula||14°54′||92°16′||168||27 (Apr.)||25 (Jan.)||2,489||473 (June)||6 (Feb.)|
climate with frost-free rainy winters and dry summers; the interior plateaus of the Cordilleras have a dry continental climate with very hot summers; and the east coast has a humid monsoonal climate.
In the tropical zone, Lower (Baja) California, the coast of the Gulf of California, and the interior of the Mexican Highlands have a dry climate. Elsewhere in the tropical zone the climate is humid, with the maximum precipitation occurring in summer. The subequatorial zone, which includes the southern part of Central America, has a permanently hot climate with humid summers and dry winters. Only the mountain regions, influenced by trade winds from the Caribbean Sea, also receive abundant precipitation during the winter.
Rivers and lakes. North America is rich in water resources. It has the earth’s longest river system (the Mississippi with the Missouri) and the greatest accumulation of fresh water (Great Lakes). The rivers of North America discharge 8,200 cu km of water annually. The water resources are distributed unevenly, however, owing to climatic and orographic conditions. The runoff varies from a few centimeters in the Great Basin to 100 cm in the Appalachians and up to 200 cm in the northwestern Cordilleras. Most of the water flows into the Atlantic Ocean. The river network of the Atlantic basin is mature and dense, and the rivers reach considerable lengths. The drainage basins of the Mississippi and St. Lawrence rivers occupy a large area.
The rivers of the Pacific basin are shorter than those of the other basins, although the rivers in the wet northern part of North America are deep. The rivers that empty into the Pacific, of which the largest are the Yukon, Columbia, and Colorado, have large gradients and often cut deep canyons with their rapid currents. The Arctic basin has a poorly developed runoff system and numerous lakes and marshes. The largest river system comprises the Finlay, Peace, Slave, and Mackenzie rivers. The hydroenergy reserves of the continent’s rivers total some 200 giga watts.
The North American rivers may be divided into four types depending on the feeding, which may be predominantly rainfall, snow-rainfall, glacier, or groundwater. The first type of river is characteristic of the coastal lowlands, the southern Appalachians, the southern Great Plains, Central America, and the West Indies, as well as the Coast Ranges in the western USA. With the exception of the rivers in the Coast Ranges, these rivers are fed by summer rains and have their maximum discharge in the autumn and spring. During the summer the runoff decreases, owing to evaporation. The rivers have a large water content and energy potential, which is exploited at the outer edge of the Piedmont Plateau, where rapids and waterfalls occur. In the drier country west of the Mississippi such rivers as the Colorado and Rio Grande become very shallow in summer, sometimes drying up in their upper reaches, although occasional heavy rains may cause flash floods. The rivers in the western USA overflow during winter rains and become shallow in summer.
The second type of river includes the rivers of the Laurentian Upland, the Mackenzie Lowland, the northern Appalachians, the northern Great Plains, and the Cordilleras, excluding the far western part of the USA and Canada. Fed by rain and snowmelt, these rivers have high water during and after the melting of the snow cover. They usually freeze over during the winter. On the interior plains and in the Appalachians high water occurs in spring and summer and low water in winter. The Missouri, Arkansas, and other rivers of the Great Plains are shallow, especially in the late summer and autumn, and have sharp peak flows in spring and early summer. In the east the rivers have stable regimes, a large water content, and enormous energy reserves, especially the Ohio River and its tributaries. A regular discharge is observed on the St. Lawrence, which drains the Great Lakes.
The rivers of the Laurentian Upland, the Mackenzie Lowland, and the Yukon Plateau (Mackenzie, Churchill, Yukon) generally flow through numerous lakes but have irregular regimes. Because of the wide distribution of permafrost rocks they receive little groundwater and become very shallow in winter. These rivers are frozen over as much as eight months of the year. High water, occurring in early summer, is accompanied by ice jams. The rivers that rise in the American Rockies also have snow and rain regimes, with summer high water.
Glacially fed rivers are characteristic of the northwestern USA, western Canada, and southwestern Alaska. They have a large water content, summer peaks, and great energy resources, especially the Columbia River. Most of the rivers of the Great Basin and the interior of the Mexican Highlands are fed by groundwater. In these desert regions small streams appear only during the winter, when evaporation is low.
The northern part of the continent, which has been subjected to glaciation, has many lakes of glacial and tectonic origin. Among them are the Great Lakes, Lakes Winnipeg, Winnipe-gosis, and Manitoba, and the Great Slave, Great Bear, and Reindeer lakes. Two large tectonic lakes, Nicaragua and Managua, lie in the Nicaraguan Trough in Central America. The Great Basin has relict lakes that have survived from the humid period of the Pleistocene; the largest of them is the Great Salt Lake. There are many lakes of lagoon origin in the coastal lowlands. Volcanic lakes occur in many parts of the Cordilleras—in Alaska, the Cascade Range, Mexico, and Central America. Despite the many measures that have been taken to limit the discharge of unpurified water, the river and lake waters of the Atlantic and Pacific basins are polluted, especially in the densely populated industrial and agricultural regions in the eastern and western parts of the continent.
Glaciers. North America’s total area of glaciation exceeds 2 million sq km. The Greenland ice cap, a fragment of Late Quaternary North American glaciation, is the largest ice sheet. Other glaciers that have survived from this time are the ice caps that cover much of Ellesmere Island and other islands in the eastern part of the Canadian Arctic Archipelago. Whereas mountain cirque glaciers are typical of the eastern islands and coastal Greenland, piedmont and shelf glaciers occur on the north coast of Ellesmere Island.
On the mainland there is extensive glaciation in southern Alaska (52,000 sq km) in the Chugach, Kenai, and particularly St. Elias mountains, where the glaciers descend to the sea. Glaciers are also found in the Brooks, Alaska, and Aleutian ranges, the Rocky Mountains, and the Canadian Coast Mountains, as well as on some peaks of the Cascade Range and the Transverse Volcanic Axis. The maximum area covered by glaciers during the Anthropogene, when the ice sheet descended to 40° N lat., was 15.6 million sq km, excluding Greenland.
Soils. North America has a great variety of soils, ranging from polar to tropical, with the most widespread soils having been created by boreal and subtropical soil-forming processes. In the northern part of the continent, zones of similar soils extend in an east-west direction. Relatively dry arctic soils and tundra arctic soils are typical for the northern islands of the Canadian Arctic Archipelago. In the southern parts of the archipelago and along the Arctic coast acidic tundra-gley soils have developed under permafrost conditions; they are unsaturated but become very wet during the warm period. Soddy-peaty subpolar soils have been formed on volcanic ashes in western Alaska and in the Aleutian Islands.
In the central parts of the Laurentian Upland and in the basins of the Yukon Plateau, cryogenic-taiga soils rich in coarse humus are found alongside surface podzols in high areas and alongside peaty-gley soils in low areas. In the southern Labrador Peninsula these soils give way to illuvial ferruginous-humic podzols, formed on light-textured moraine and fluvioglacial deposits. In the southwestern part of the Laurentian Upland and on the northern Great Plains the soils are soddy podzols. They typically have a shallow humus horizon, especially on the Great Plains, where gray forest soils have developed together with so-Iodized soils on ancient lake deposits. With the exception of the soils formed on carbonate moraine or lake deposits, all of these soils are used comparatively little in farming.
In the southern part of the temperate zone and in the sub-tropics, similar soils are often distributed in submeridional zones or compact masses. The Great Lakes region and the northern Appalachians have brown forest soils, unsaturated in the north and saturated in the south. These soils form under conditions of abundant atmospheric moisture and are quite fertile, although they often contain a compact impermeable subsoil horizon and require drainage.
To the south of the Great Lakes and in the northwestern part of the Central Plains, the chernozem-like soils of the prairies, either weakly acidic or neutral and with a high humus content, were formed under moderately humid climatic conditions. Near the Great Plains they give way to chernozems, which occupy a much smaller area in North America than in Eurasia. The chernozems are strongly leached; in the north (Canada) they are found together with meadow chernozems. Chestnut soils, forming large pockets on the Great Plains and Columbia Plateau, are much more widely represented. Saline brown semidesert soils and solonchaks have developed in the Great Basin, with its dry continental climate.
In the southern parts of the North American plains variations in soil are even more closely linked to moisture. In the humid southeastern part of the continent red and yellow soils have developed on marine clayey and sandy loam deposits; this is the largest accumulation of such soils in the world. The soils are highly productive but require much fertilization. West of the Mississippi lie the reddish black soils of the subtropical prairies and the cinnamon-colored and gray-cinnamon soils of the shrub steppes. Gray earths and the primitive soils of subtropical deserts characterize the interior of the Mexican Highlands; tropical desert soils are found in Lower (Baja) California.
In the low-lying parts of Central America the predominant soils are the red-yellow ferralitic soils of humid forests and the red ferralitic soils of savannas. Various types of mountain soils are found on the slopes of the Cordilleras; brown-forest mountain soils prevail in humid regions and cinnamon-colored mountain soils in dry regions.
Intensive cultivation over a long period of time has destroyed the topsoil in many parts of the continent, expecially in the Appalachian foothills and on the Great Plains, necessitating drastic measures to control soil erosion.
Plant life. In general, the flora of North America belongs to the Holarctic floristic region. Only the southern part of the Mexican Highlands and Central America are included within the Neotropical floristic region. The vegetation of North America is very similar to that of Eurasia. North of 47° N lat. the vegetation zones run from east to west and from northeast to southwest; south of that point they extend from north to south.
In the northern parts of the Canadian Arctic Archipelago and in Greenland the soil supports a scanty arctic desert vegetation consisting chiefly of crustose lichens, mosses, and a few species of higher vascular plants.
Tundra occupies the southern part of the archipelago and stretches in a broad band along the Arctic coast of the mainland. Moss and lichen formations predominate in the northern part of the tundra and shrub formations in the south. Spruce, both black and white, tamarack, and balsam poplar form the northern boundary of tree growth. The forest-tundra, stretching in a band roughly 100-200 km wide, includes coniferous forests (along river valleys), tundras, and open woodlands (on watersheds). In the western part of the continent, on the Alaska Peninsula and the Aleutian Islands, forest-tundra is replaced by oceanic meadows, which develop in a marine climate with summer temperatures that are not warm enough to permit tree growth. The grass cover consists of high grasses, such as reed bent grass and brome, and various forbs.
Forests occupy roughly one-third of the continent. The most extensive forests are those of the temperate belt, divided into taiga, coastal coniferous, mixed, and broadleaf forests. The taiga consists chiefly of dark coniferous species with an admixture of small-leaf species (black and white spruce, balsam fir, aspen, and paper birch) and of pine woods (Weymouth and jack pine), growing on sandy deposits. Coastal coniferous forests are found on the west coast of Canada and in the American Northwest in valleys and coastal lowlands and on the lower slopes of the Cordilleras. The most common species are Sitka spruce, Douglas fir (Pseudotsuga), western red cedar (Thuja), hemlock (Tsuga), and various pines. To the south there are also such broadleaf trees as Oregon oak. At its upper limit (900-2,000 m) the coastal coniferous forest is replaced by a mountain taiga fir and spruce forest, which in turn gives way to mountain tundra.
Mixed forests are found around the Great Lakes and in the northern Appalachians. On the dry watersheds with loam top-soils grow forests of maple, elm, linden, birch, and hemlock. Pine woods and tracts of scrub oak and birch occur on sandy river terraces, and spruce and fir woods cover moraine ridges. Broadleaf forests are found in the central and southern Appalachians and in the eastern Central Plains. Owing to the great age of the flora of this region, the forests are composed of numerous species, including dozens of oak species, chestnut trees, beeches, hickories, and relict tulip trees. Above 700–1,000 m the slopes of the Appalachians are covered by mixed and coniferous forests on podzolic soils.
In the subtropics there is a zone of evergreen mixed forests in the east and one of evergreen coniferous forests in the west. Evergreen mixed forests are widespread in the eastern foothills of the southern half of the Appalachians (Piedmont Plateau) and on the coastal lowlands. On marine terraces and plateaus the tree stand is composed of evergreen oaks, elms, magnolias, and numerous species of pine covered with lianas. Along river valleys the woods contain oaks, magnolias, yews, and swamp cypress. In sandy regions, primarily along the coast, there are pure pine forests with low palms in the undergrowth.
Coniferous forests cover the coast of California and the foothills of the Sierra Nevada. They include sequoia forests, dry pine forests, and forests with a mixture of fir, piñon (Pinus cembroides), Douglas fir, and other conifers. At higher elevations they are replaced, successively, by spruce and fir forests, subalpine meadows, and alpine meadows. In the driest southern regions the forests give way to hard-leaved evergreen scrub oak, called chaparral.
The continental interior is occupied by forest-steppes, steppes, semideserts, and deserts. The forest-steppe zone stretches from the Cordilleras eastward across the Canadian Great Plains and southward across the western part of the Central Plains. On the Great Plains grass and forb meadow steppes alternate with small-leaved forests, and on the Central Plains tall beard-grass steppes (prairie) are interspersed with open woodlands of oak and hickory. The forest-steppe vegetation has not been preserved in its natural form.
Steppes are found on the Great Plains, on the Columbia Plateau, and in the Central Valley. Feather-grass and wheatgrass steppes are found in the eastern part of the American Great Plains; elsewhere, dry low-grass steppes of grama grass, buffalo grass, wheatgrass, and species of Aristida predominate. In the southern Great Plains the dry steppes give way to a subtropical mesquite savanna. The Central and Great Plains are used intensively for agriculture.
Deserts and semideserts occupy the Great Basin, the eastern Colorado Plateau, and areas northwest of the Gulf of Mexico. At the eastern foot of the American Rockies there are semideserts with psammophytic grasses and sagebrush growing on brown soils. Over the remaining territory semideserts and deserts alternate, depending on the topography and moisture. North of 37° N lat. the vegetative cover consists of such semishrubs as sagebrush, orache, Sarcobatus vermiculatus, and saltwort; to the south grow shrubs (creosote bush, ocotillo) and succulents (cacti, yuccas). The mountain ranges and higher parts of plateaus that rise above the basins are covered with grasses and open woodlands of pine and juniper or pine and oak (in the south). On the upper slopes of high mountains the grasses and open woodlands are replaced by spruce and fir forests and alpine meadows.
The southern parts of the Mexican Highlands, southern Florida, Central America, and the West Indies have a tropical vegetation. In the most humid areas, chiefly at the foot of windward mountain slopes, grow evergreen rain forests, complex in composition, consisting of giant trees (covered with lianas and epiphytes) and bamboo groves. At higher elevations these forests give way to humid deciduous tropical forests of beech, linden, and oak and to subtropical evergreen mountain forests and brushland. The leeward slopes support tropical savannas that include dry low thorn forests composed chiefly of species of the legume family. Mangrove thickets fringe the coast.
The vegetation and topsoil of North America have been greatly altered by man, especially in the USA. The natural vegetation of the prairies has been almost completely destroyed, and the forests have been diminished. Broadleaf forests, now found only on mountain slopes, are poorer in composition. The mixed forests of the temperate and subtropical zones and the coniferous forests of the Cordilleran West have been greatly reduced by logging and fires.
Animal life. The fauna of the larger, nontropical, part of the continent closely resembles that of analogous parts of Eurasia, owing to the former land bridge between the continents. Thus, the nontropical parts of North America and Eurasia may be united into one large zoogeographical region, the Holarctic. However, certain distinctive characteristics of the fauna justify classifying the North American part as an independent region, the Nearctic, in contrast to the Palaearctic region of Eurasia.
The tundra zone is inhabited by reindeer (caribou), polar bears, arctic foxes, lemmings, snowshoe rabbits, snowy owls, and ptarmigans. The musk ox is found only in the northern Canadian Arctic Archipelago and Greenland. The most common taiga animals are the moose, wapiti, American marten, brown bear, Canada lynx, wolverine, beaver, porcupine, otter, fisher, red squirrel, and flying squirrel. The number of animals, particularly fur-bearing species, has decreased sharply.
Even more depleted is the fauna of the mixed and broadleaf forests, which includes such native species as the Virginia deer, skunk, gray fox, bobcat, gray squirrel, star-nosed mole and, among birds, the swallow-tailed kite and wild turkey. Crice-tines, shrews, and woodchucks are widely found. In the subtropical southeastern part of the continent, in addition to animals common to broadleaf forests, there are such tropical species as alligators, caimans, ibises, flamingos, pelicans, and hummingbirds (one species occurs as far north as Alaska).
The animals of the steppes and forest-steppes have been largely destroyed, among them the bison, now found only in preserves, the pronghorn antelope, the brocket, which has survived in mountains, the coyote, and the kit fox. Much more numerous are rodents (ground squirrels, prairie dogs), the weasel Putorius eversmanni, badgers, kangaroo mice, and birds (ground owl, prairie chicken). Typical of the mountain forests of the Cordilleras are bighorn sheep, grizzly bears (Alaska), and mountain goats. On the desert-steppe high plateaus are numerous reptiles, among them poisonous reptiles (rattlesnake, gila monster) and horned lizards. In Central America and the West Indies and in some parts of the southern Mexican Highlands tropical animals predominate, including South American species: armadillos, monkeys, bats, hummingbirds, parrots, tortoises, crocodiles, and lizards.
Of the 55 national parks in North America, 19 are in Canada, 27 in the USA, six in Mexico, and three in Cuba. In addition to protecting flora and fauna, they are major tourist attractions. The most famous national parks are Yellowstone, Grand Canyon, Yosemite, Banff, Jasper, Sequoia, and Everglades.
Natural regions. Spanning the arctic, subarctic, temperate, subtropical, tropical, and subequatorial zones, North America is divided into two large parts, the plains non-Cordilleran East and the mountainous Cordilleran West, which in turn are subdivided into regions. The non-Cordilleran East includes Greenland, the Canadian Arctic Archipelago, the Laurentian Upland, the Central Plains, the Great Plains, the Appalachians, and the Coastal Lowlands.
About 80 percent of Greenland, the largest island in the world, is covered by ice. In the interior the ice forms a solid sheet with an average thickness of 2,300 m. Along the southwestern, northern, and northeastern coasts there are ice-free stretches of land 200–250 km wide. The climate is arctic and marine subarctic (south of 68° N lat.), and the vegetation is limited to tundra species. The Canadian Arctic Archipelago is one of the world’s largest island groups. With respect to natural features the southern and western islands are similar to the northern part of the continental mainland, and the northeastern islands resemble northern Greenland. The archipelago’s location in the high arctic latitudes and its harsh arctic climate have caused the development of tundra and arctic desert landscapes.
The Laurentian Upland, the principal part of the Canadian
Shield, has a relatively elevated (150–600 m) and strongly pene-plained surface. Virtually the entire territory is hilly, with many marshes and lakes; the region is covered by forest and tundra vegetation. The climate, strongly affected by the arctic, is marked by low temperatures, strong winds, and high humidity. The Central Plains occupy the eastern part of the Mississippi basin. Surface features are related to the configuration of the Paleogene and Neogene peneplain, complicated in the north by glacial deposits. There are significant temperature variations between the northern and southern parts of the Central Plains in all seasons but especially during the winter, which is one of the main reasons for the sequence of landscapes from taiga to subtropical forests. The Great Plains, vast submontane plateaus of the Cordilleras, are covered by dry steppes. There are shallow rivers flowing through deep valleys and extensively developed systems of gulleys (badlands).
The Appalachians are a system of folded mountain ranges, valleys, and plateaus. Moderated by the Atlantic Ocean, the climate is temperate in the north and subtropical in the south. The Coastal Lowlands have a flat topography and are very swampy. The region’s warm moist oceanic climate favors the development of a rich, primarily subtropical, flora.
The Cordilleran West may be divided into the Alaskan Cordilleras, the Canadian Cordilleras, the American, or Southern, Cordilleras, and the Mexican Highlands. The Alaskan Cordilleras occupy the northern part of the Cordilleras and include the entire state of Alaska and the Canadian part of the Yukon Plateau. High mountain ranges with thick glaciation predominate in the south, and high plateaus are found over the remaining territory. Altitude zonation is represented by forest tundra in the river valleys and mountain tundra on the high plateaus. Permafrost occurs everywhere. The Canadian Cordilleras, the narrowest part of the Cordilleras, consist for the most part of high mountain ranges with extensively developed ancient glacial forms and contemporary glaciation. The climate is temperate and ranges from humid to dry. The spectrum of altitude zones includes steppes in the intermontane valleys, forest-steppes on the high plateaus, mountain coniferous forests on the slopes, and alpine meadows on the peaks.
The American, or Southern, Cordilleras constitute the highest part of the Cordilleras. High ranges covered with snow fields and glaciers adjoin vast undrained desert plateaus. The subtropical climate is Mediterranean on the coast and dry in the interior. On the slopes of the high ranges there are zones of mountain pine forests, subalpine coniferous open woodlands, and alpine meadows. In the Mexican Highlands the topography is dominated by high plateaus and highlands, in places very rugged. There are frequent earthquakes and volcanic eruptions. The climate is tropical and mostly dry. On the windward slopes grow low thorn forests (at the foot) and deciduous tropical forests; coniferous forests are found at the peaks. Creosote bush deserts, high-mountain succulent deserts, cactus-acacia savannas, and mountain coniferous and hard-leaved forests occur in the interior.
G. M. IGNAT’EV
After establishing settlements in Greenland, the Norsemen discovered Newfoundland and part of the coast of the Labrador Peninsula between the 11th and 13th centuries. They also sailed into Baffin Bay as far as 74° N lat. Their discoveries, however, were not known in the Old World. Between 1492 and 1503, Columbus headed four Spanish expeditions that discovered the Bahamas, Cuba, Haiti, the Lesser Antilles, Puerto Rico, Jamaica, and the Caribbean coast of Honduras, Nicaragua, Costa Rica, and the Isthmus of Panama. J. Cabot and S. Cabot sailed along the east coast of North America in 1497–98 and the Portuguese navigator G. Corte-Real, in 1500–1501. Circa 1504, French seafarers entered the Gulf of St. Lawrence.
In 1513 the Spaniard V. Núñez de Balboa crossed the Isthmus of Panama and reached the Gulf of Panama on the Pacific Ocean, and J. Ponce de León discovered the Florida Peninsula. Between 1517 and 1519 the Spanish expeditions headed by F. de Córdoba, J. de Grijalva, and A. de Pineda discovered the Yucatán Peninsula and the southern, western, and northern shores of the Gulf of Mexico. From 1519 to 1524, Spanish conquistadores led by H. Cortés crossed the Meseta Central, reaching the Pacific Ocean, and then traveled southeast through Guatemala and Honduras to the Gulf of Fonseca. Meanwhile, a Spanish naval expedition headed by G. González Dávila sailed northwest from the Gulf of Panama to the Gulf of Fonseca. Disembarking on the Nicoya Peninsula along the way, Dávila discovered Lakes Nicaragua and Managua.
In 1524, G. da Verrazano, an Italian navigator in the French service, explored the east coast of North America from 34° to 46° N lat. In 1528, P. de Narvaez’s Spanish expedition, following the northeastern coast of the Gulf of Mexico, discovered the Mississippi delta. A member of the expedition, A. Cabeza de Vaca, crossed the southern Great Plains and the Rio Grande basin between 1529 and 1536. In 1532–33, H. Cortés discovered the southern part of Lower (Baja) California. In 1540–41 the Spaniard F. de Coronado traveled north across the Colorado Plateau, the southern Rocky Mountains, and the Great Plains to 40° N lat., while his ships sailed up the Gulf of California to the lower reaches of the Colorado River. H. De Soto’s Spanish expedition, traveling north and west from Florida between 1540 and 1543, discovered the southern Appalachians and the Alabama and Tennessee rivers and followed the Mississippi River from its confluence with the Arkansas River to its delta. In 1542–43 the Spanish navigator J. Cabrillo sailed up the west coast of North America to 40° N lat.
Searching for the Northwest Passage, the French explorer J. Cartier sailed around the north coast of Newfoundland in 1534–35 and discovered the southeastern coast of the Labrador Peninsula, Prince Edward Island, the Gaspé Peninsula, Anti-costi Island, and the St. Lawrence River. Between 1576 and 1631, English expeditions headed by M. Frobisher, J. Davis, H. Hudson, T. Button, R. Bylot, W. Baffin, L. Foxe, and T. James explored the coast of Baffin Bay and Hudson Bay and reached the Foxe Basin.
In 1609 the French navigator S. de Champlain discovered the northern Appalachians, and between 1615 and 1648, Cham-plain, his agents (among them E. Brulé), and several Jesuits (including J. de Brébeuf) discovered the Great Lakes. In 1669, Sieur de La Salle discovered the Ohio River, and in 1673, L. Jolliet sailed down the Wisconsin and Mississippi rivers as far as the Arkansas River, discovering the mouth of the Missouri River along the way. Later, La Salle spent three years (1678–81) exploring the water routes from the St. Lawrence River, through the Great Lakes, to the Mississippi, which he navigated from its confluence with the Illinois River to the sea.
In 1648 the Russian explorers F. Popov and S. Dezhnev sailed from the Chukchi Sea to the Pacific Ocean, proving that North America is separated from Asia by a narrow strait (the Bering Strait) near 65° N lat. In 1690–91 the English explorer H. Kelsey, traveling southwest from Hudson Bay, crossed the Laurentian Upland and discovered the Saskatchewan River. Between 1734 and 1749 the French explorer P. G. de Varennes and his sons discovered several lakes in central Canada, among them Lakes Winnepeg and Manitoba, and the Missouri Plateau.
In the northwest the Russians I. Fedorov and M. Gvozdev discovered the Seward Peninsula in 1732, and in 1741, V. Bering and A. Chirikov discovered part of the coast of the Gulf of Alaska, the Alexander Archipelago, Kodiak and nearby islands, and several of the Aleutian Islands. Between 1759 and 1764, A. Tolstykh, S. Glotov, S. Ponomarev, and others discovered the Rat, Andreanof, and Fox islands and part of the Alaska Peninsula. P. K. Krenitsyn and M. D. Levashev essentially completed the discovery of the entire Aleutian chain in 1768–69.
In 1774–75, Spanish seamen explored the west coast of North America to 55° N lat., discovering the mouth of the Columbia River, the west coast of Vancouver Island, and some of the Queen Charlotte Islands along the way. In 1776 the Franciscan monk F. Garcés crossed the Mojave Desert and discovered the Central Valley, and the monk S. Vélez de Escalante explored the Great Basin. In 1778 the British navigator J. Cook sailed up the west coast of North America to 70°20’ N lat., exploring en route the Gulf of Alaska and the eastern part of the Bering Sea, where he discovered Norton Sound.
Between 1770 and 1787 several British explorers, including S. Hearne and J. Frobisher, discovered chains of lakes in northern Canada, including Great Slave Lake and Lake Athabasca, as well as the mighty Mackenzie River, which flows through them. A. Mackenzie sailed down the river to the Arctic Ocean in 1789. In 1792, R. Mackenzie discovered Great Bear Lake, and in 1792–93, A. Mackenzie crossed North America from east to west, including the northern Rocky Mountains, and was the first to see the Fraser River. G. Vancouver completed the discovery of Vancouver Island and the Queen Charlotte Islands from 1792 to 1794, and D. Thompson explored the Columbia basin.
Between 1784 and 1795 the Russian explorers G. I. Sheli-khov, A. A. Baranov, G. A. Sarychev, and D. I. Bocharov completed the discovery of the Alaska and Kenai peninsulas. From 1816 to 1844, O. E. Kotsebu, M. N. Vasil’ev, A. K. Etolin, A. Klimovskii, I. F. Vasil’ev, V. Malakhov, P. Kolmakov, and L. A. Zagoskin discovered Kotzebue Sound, Nunivak Island, the Copper, Susitna, Nushagak, and Kuskokwim rivers, the lower and middle reaches of the Yukon River, the Chugach, Wrangell, and Kuskokwim mountains, and part of the Alaska Range. The sources of the Yukon, its upper reaches, and the Yukon Plateau were discovered between 1843 and 1850 by the British explorer R. Campbell.
Crossing North America from 1804 to 1806, the Americans M. Lewis and W. Clark followed the Missouri River from its mouth to its headwaters, which they discovered, and then pushed on over the central Rocky Mountains. In 1806–07, Z. Pike discovered the highest peaks in the Rocky Mountains in the southern Rockies near the headwaters of the Arkansas River. Between 1824 and 1853, J. Bridger, P. Ogden, B. de Bonneville, K. Carson, and J. Fremont explored and mapped the Central Valley and the Great Basin, discovering the Great Salt Lake and various nondraining rivers such as the Humboldt.
The major British discoveries in the Canadian arctic during the 19th century were related to the quest for the Northwest Passage. In 1818, John Ross surveyed the east coast of the islands of Devon and Baffin. Between 1819 and 1825, W. Parry discovered three straits near 74° N lat., the islands adjacent to them, and the Melville Peninsula, revealing that Baffin Land was an island. J. Franklin’s expeditions in 1821 and 1826 (J. Richardson took part in the second) explored large stretches of the north coast from 149° to 114° W long., discovering the Dolphin and Union Strait, Coronation Gulf, and the southwestern shore of Victoria Island. Between 1829 and 1831 an expedition headed by John Ross, in which James Ross participated, discovered and explored the Boothia Peninsula. From 1837 to 1839, P. Dease and T. Simpson were the first to explore two segments of the north coast between 156° and 98° W long., where they found the Kent Peninsula, Dease Strait, Queen Maud Gulf, Simpson Strait, the Adelaide Peninsula, and the southern shores of King William and Victoria islands.
After reaching the arctic in 1845, Franklin’s expedition disappeared without a trace. Between 1848 and 1854 parties headed by F. McClintock, H. Kellett, R. Collinson, and R. McClure explored the entire north coast, establishing the outlines of the continent. During these expeditions the Prince of Wales and Prince Patrick islands were discovered, and the entire coasts of Banks, Melville, Bathurst, and Somerset islands was explored. Between 1858 and 1871 the Americans E. Kane, I. Hayes, and C. Hall discovered the Kane and Hall basins and Kennedy and Robeson channels and were the first to reach the Lincoln Sea. In 1875–76, G. Nares’ British expedition discovered the north coast of Ellesmere.
From 1898 to 1902, O. Sverdrup’s Norwegian expedition discovered the west coast of Ellesmere Island and then the Sverdrup Islands. Between 1914 and 1917 the Canadians V. Stefansson and S. Storkerson essentially completed the discovery of the north coast of Victoria Island and of the entire Canadian Arctic archipelago by finding the Mackenzie King, Borden, Lougheed, and other islands in the northwest.
In the late 19th and early 20th centuries J. Powell, J. Dawson, A. Brooks, and other American and Canadian geologists completed the exploration of the Rocky Mountains, the Laurentian Upland, the Yukon Plateau, and the Alaska Range (with Mount McKinley, the highest point in North America) and discovered the Brooks Range. From 1884 to 1904 the Canadians A. Low and J. Tyrrell established the hydrographic network of Labrador and northern Canada.
I. P. MAGIDOVICH
Anthropological and ethnic composition. The present population of North America includes representatives of the three major human races. The indigenous pre-European population (Indians and Eskimos) and some later arrivals from Asia belong to various branches of the Mongoloid race; the descendants of European immigrants, to the Caucasian race; and the people of African origin, to the Equatorial, or Negro-Australoid, race. Mixed racial groups, including mestizos and mulattoes, constitute a large part of the population. Most of the population of North America consists of the descendants of European and, to a much lesser extent, Asian immigrants who came here between the 16th and 19th centuries and of the descendants of slaves brought from Africa in the 17th and 18th centuries. Remnants of the native peoples—Indians, Eskimos, and Aleuts-constitute only a small part of the population.
The modern population of Mexico and mainland Central America evolved through the intermingling of Spaniards and local Indians. Anthropologically, the people are mestizos, but they speak Spanish. The Caribbean islands are inhabited chiefly by Negroes and mulattoes, the descendants of African slaves and European colonists (Spanish, English, French, Dutch). In the islands most people speak the corresponding European languages.
English is the dominant language in the USA, and both English and French are the major languages of Canada. In these two countries a constant stream of immigrants from various countries gives rise to new transitional groups that are gradually being assimilated by the American and Anglo-Canadian nations. Moreover, in the USA there is a special group of Americans, the Negroes. Because of centuries of discrimination and segregation they have preserved many anthropological traits and some cultural traits, although they speak only English.
The most numerous English-speaking peoples of North America are the Americans of the USA and the Anglo-Canadians. (In 1973, there were an estimated 190 million Americans, including 25 million Negroes, and some 10 million Anglo-Canadians.) Among other English-speaking groups are the peoples of Jamaica (2 million), Trinidad (950,000), Barbados (240,000), the Bahamas (175,000), and Belize (120,000). Among immigrants being assimilated in the USA and Canada who speak English to some extent are immigrants from Italy (4.5 million), Germany (3.8 million), Poland (2.6 million), Russia (2.5 million), the Scandinavian countries (1.8 million), and Puerto Rico (1.4 million).
The Spanish-speaking peoples of North America are the Mexicans (roughly 50 million, including some 4 million in the USA), Cubans (8.8 million), and the bulk of the population of the Dominican Republic (4.5 million), El Salvador (3.5 million), Guatemala (3.1 million), Puerto Rico (2.9 million), Honduras (2.5 million), Nicaragua (1.9 million), Costa Rica (1.9 million), and Panama (1.5 million). French Canadians, the second largest national group in Canada, number some 6.6 million people. Other French-speaking groups in North America include the people of Haiti (roughly 5 million), Martinique (340,000), and Guadeloupe (340,000).
Indians have survived chiefly in southeastern Mexico and western Guatemala, in the inaccessible parts of Honduras, Panama, and the other Central American countries, in the interior regions of Alaska, in northern Canada, and on reservations in the USA and Canada. They are increasingly adopting the languages of the dominant peoples around them: Spanish, English, or French. The total number of North American Indians probably does not exceed 10 million. In the Far North, along the coasts of the mainland and of the Arctic islands, there are some 70,000 Eskimos. The surviving Aleuts, about 5,000 persons, live on the Aleutian Islands. With respect to religion, most of the people of North America belong either to the Catholic Church or, chiefly in the USA and Canada, to one of the many Protestant denominations. Other faiths, including the Orthodox, Jewish, and Buddhist, are also represented. (See Table 2 for the ethnic makeup of North America.)
M. IA. BERZINA
The first independent state in North America, the United States of America (USA), was formed in 1776 during the American Revolutionary War. It is now the foremost capitalist country in the world. The present boundaries of the USA were established through the expropriation of land belonging to the indigenous Indians (including the colonization of western territories), as well as through wars and other acquisitions, such as the purchase of Alaska and the Aleutian Islands from tsarist Russia in 1867.
Haiti won its independence in 1804 after an uprising against the French colonialists. At the same time, Spanish domination in the eastern part of the Island of Haiti was undermined, and in 1844 it became the Dominican Republic. During the War of Independence of the Spanish-American Colonies (1810–26), Mexico, Guatemala, Honduras, Costa Rica, Nicaragua, and El Salvador achieved political independence. In 1867, Canada was granted the status of a dominion within the British Empire. It is now an independent state within the Commonwealth; in 1949, Newfoundland joined Canada.
After the Spanish-American War (1898), Cuba was declared an independent republic, although in fact it became a US protectorate in 1901. The independence of Panama was proclaimed in 1903, but the USA imposed on the Panamanians a treaty giving it perpetual use of a zone in which to build and operate an interoceanic canal. The victory of the Cuban Revolution in 1959 led to the establishment of the first socialist state in the Americas and stimulated an upsurge in the liberation movement on the entire American continent.
Several former British colonies in the West Indies have achieved independence: Jamaica (1962), Trinidad and Tobago (1962), Barbados (1966), the Bahamas (1973), and Grenada (1974). Nevertheless, in the mid-1970’s a number of territories in North America were still possessions of the USA, Great Britain, France, and the Netherlands. Greenland belongs to Denmark. (The political subdivisions of North America are given in Table 3.)
|Table 2. Ethnographic makeup of America|
US and Canadian Jews
Swedes, Norwegians, Danes,
People of Barbados and
peoples of the Lesser
Antilles and the English-
speaking population of
French-speaking peoples of
the Lesser Antilles
Athapaskans(Chipewyan, Kutchin, Navaho,
Apache, and others)
Algonquians(Ojibwa [Chippewa], Cree,
Montagnais, Naskapi, Menomini,
Arapaho, Siksika [Blackfoot], and others)
Wakashans (Nootka, Kwakiutl)
Sioux (Dakota and others)
Muskogee (Seminole, Creek, and others)
Chontal of Oaxaca
Shahaptian, Tsimshian, and others
Yaqui and Mayo
Cora, Huichol, Tepehuan
Pima and Papago
Pipil and others
Chol, Chontal of Tabasco
Tzeltal, Tzotzil, Tojolabales
Mam, Quiche, Cakchiquel, Kekchi
Totonac, Tepehua, Popoloca of Veracruz
Mixe and Zoque
Mixtec, Popoloca of Puebla, Mazatec
Other Indian language families
Chibcha (Cuna and others)
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