The surface of North America is very diverse. With an average height of the continent of 720 m above sea level, most of its heights range from 200 to 500 m, lowlands account for 20%. More than 25% of the territory has altitudes above 1000 m. The highest point in North America is Mount McKinley - 6193 m, the lowest is Death Valley - 85 m below sea level.
Unlike other parts of the world, typical for the continent is the meridional extension of the highest mountain systems along its periphery - the Cordillera in the west and the Appalachians in the east. The nature of the relief left its mark on the climatic conditions of its different parts, as well as on other components of nature, increasing the differences between the western and eastern regions.
The continent is based on the Precambrian North American Plate, which occupies approximately half of its surface, most of Greenland and the southeast of the Canadian Arctic Archipelago. About 60% of the platform surface has almost no sediment cover and protrudes to the surface in the form of the Canadian or Laurentian shield - one of the largest shields in the northern hemisphere. The shield is formed by Archean and Proterozoic gneisses, granites and other crystalline rocks.
The Canadian Shield once covered almost all of North America east of the Rocky Mountains. More precisely, it was he who was then North America. Then the southern part of it sank and was flooded with the sea. And when the sea retreated again, not a shield appeared from under the water, but thick layers of marine sediments: limestone, clay, sand. They settled on the surface of the shield and covered it with a layer several kilometers thick. It is they who now form the surface of the United States and the western part of Canada.
Even a long time ago, the Canadian Shield was under pressure from neighboring areas earth's crust gave a number of cracks. The middle sank along the cracks and fell through. The sea immediately flooded the formed depression. This gap in the shield is clearly visible on the map; it is occupied by Hudson Bay.
The Canadian Shield, in the part that now comes to the surface, was buried for many years under ice, the thickness of which reached 2-3 km. From the Keewatin area, west of Hudson Bay and Labrador, the ice blanket spread both inward into Hudson Bay and outward to the edges of the crystalline shield and beyond.
When the glacier melted, the depressions along the edges of the shield, formed along cracks or covered with ice, filled melt water- the Great Lakes and a chain of other, also very large, “almost large” lakes arose: Winnipeg, Athabasca, Great Slave, Great Bear. These lakes were connected by rivers that carried excess melt water into the ocean: the St. Lawrence River flowed to the northeast, and the Mackenzie River to the northwest, just outside the shield. The rivers made channels to bypass the glacier, because it did not yet allow them to take the shortest route to Hudson Bay. Some of the water flowed south into the Gulf of Mexico through the Mississippi River.
The glacier could not turn the Canadian Shield into an absolute plain, because different places it had different hardness. Near the “ram’s foreheads” there are “curly rocks”, the surface of which resembles the wavy wool of a sheep. “The sheep's foreheads” are in some places polished with ice to a shine, in some places they are streaked with parallel scratches - traces of the stones that he carried behind him. From the direction of these scratches they learned where the glacier was coming from and where it was moving.
Countless humps and depressions on the surface of the shield are scattered in complete disorder. When the glacier melted, each depression turned into a lake, which is why there are many lakes in northern Canada. The land between them is like thin lace, all consisting of an intricate network of islands and isthmuses. The lakes lie at different heights, and the rivers run down one after another, rapids and waterfalls.
Therefore, development modern forms surface of North America is a manifestation and consequence of the close interaction of endogenous and exogenous processes. As a result, the following orotectonic regions were formed within North America: the Laurentian Plateau, the Cordillera, the Appalachians, the Central Plains, the Great Plains and the Coastal Lowlands.
Almost the entire north of the continent is occupied by the Laurentian Plateau, which belongs to the mainland of the Canadian Shield. Its area is over 7 million square meters. km.
In most of this plain, Archean-Proterozoic crystalline rocks (granites, gneisses and others) come directly to the surface. Only south of Hudson Bay the crystalline rocks are covered by Cambrian and Silurian sedimentary rocks. The Laurentian Plateau is bowl-shaped. In his internal parts absolute elevations vary between 180-200 m, and along the periphery - 300-500 m. In the east of this area, within Labrador, in the Neogene time, the territory was uplifted, now the Tornhut horst spine, whose height is over 1500 m, is clearly visible here. New uplifts of individual parts also occurred in other areas, due to which the relief experienced rejuvenation.
The insular part of the Laurentian Plateau is characterized by great dissection. The uplifts that took place here in the Neogene were accompanied by intense volcanic activity. In particular, on the east coast of Greenland, crystalline rocks are covered with a layer of basalt, which forms a chain of high mountains and nunataks.
The surface shapes of the Arctic islands are associated primarily with icing. The largest glaciers are concentrated in Greenland, and smaller ones are on the islands of Baffin Island, Devon, Ellesmere, Axel Heiberg, and Melville.
In the south, the Laurentian Plateau passes into the region of the Central Plains. Over large areas of this territory, Pre-Cambrian rocks are covered with sediments of different geological ages. The stability of the sediment layer is uneven, which creates conditions for the development of cuesta landforms along the entire periphery of the plain. Yes, south of the Great Lakes and between them the surface is composed of Lower Paleozoic rocks, and the relief is clearer than cuestas that formed in dense Silurian limestones (for example, the Niagara Falls ledge).
Anthropogenic icing also left its mark on the relief of the cuesta area. The rock roots of this area are buried under moraine and fluvio-glacial sands.
Bottom moraine and hilly bottom moraine topography is quite common. Often the height of bottom-moraine pasas reaches 20-50 m relative height; in some places they are crowned by high parts of the cuesta.
The surface of the watershed areas of the southern Central Plains is flat, but the coastal areas are dissected by a dense network of ravines, especially in the far south. In addition to erosion, karst landforms are well developed here.
To the west of the Central Plains lies the Great Plains, or Prairie Plateau. The Great Plains are a system of stepped plateaus that descend from the Cordillera to the east. Their height ranges from 500 m in the east to 1600-1700 m in the west, and their length from north to south is over 4000 km. The surface of the Great Plains is composed of rocks, mainly sediment of the Mesozoic and Cenozoic ages, which are covered with alluvial, aeolian, and in the northern part - glacial material. The rivers that flow from the Cordillera have divided the plateau into deep valleys into a mesa.
Most characteristic feature The relief of the Great Plains is a combination of various erosion forms. The surface of riverine areas is especially rugged. The slopes of neighboring ravines, intersecting here, form numerous interlacings of sharp ridges. This is a badland - completely unsuitable for economic use land.
The topography of the northern Great Plains was significantly affected by icing. The valleys here are very wide, and their slopes are smooth, the watershed areas are mountainous with a disorderly accumulation of sandy-clayey material and dotted with lakes.
There are no glacial deposits in the southern Great Plains. Vast plateaus composed of Upper Paleozoic deposits are dissected by a network of deep gorges. These gorges, 200-300 m deep, make it difficult to build paths.
The Great and Central Plains in the south become the alluvial Mississippian lowlands, which merge with the Coastal Lowlands (Atlantic and Mexican).
The lowlands were formed both in the Mesozoic and Cenozoic, as a result of the subsidence of the Paleozoic folded basement. The relief of the lowlands is associated with a rapid epeirogenic uplift of the territory in place of territories previously flooded by the sea.
The surface of the Mexican Lowland is almost ideally flat with absolute elevations of up to 100 m. The hydrological network is developed. Near the sea, rivers flow in their sediment, sometimes even higher than the surrounding area. Near the coast the lowland is swampy.
In some places, the surface is composed of limestone rocks, and therefore karst phenomena have a significant development here (Florida, Yucatan and others).
The Atlantic lowland in the west is surrounded by the escarpment of the Piedmont plateau. It is composed of a thickness of rocks (limestones, sandstones, clays) and sediment up to 1000 m thick, which lie on a Paleozoic crystalline basement. The average height of the lowland is 100 m. Its surface is dissected by the valleys of numerous rivers.
The eastern edge of North America occupies a belt of ancient rejuvenated mountains - the Appalachians.
The mountains stretch in the form of a series of longitudinal spines from the southwest (from Alabama, in the southern United States) to the northeast to Cape Gaspé (in the Gulf of St. Lawrence) and further to the island of Newfoundland. The length of the mountains is over 2000 km, width 200-300 km, medium height 1000-1300 m, and individual peaks reach 2000 meters or more.
The deep Hudson-Mohawk tectonic basin divides the Appalachians into Northern and Southern. The northern Appalachians are lower, almost everywhere composed of metamorphic and crystalline rocks predominantly of the Lower Paleozoic age. During the Mesozoic and Cenozoic periods, the mountains experienced uplift, and anthropogenic icing gave them a dome-shaped outline. Now this part of the mountains has the character of a leveled plateau with a height of 400-600 m, above which individual mountain ranges and “spines” rise: the Adirondacks with the peak of Mars (1628 m), the Green Mountains in the west (1200 m), the White Mountains in the east with Mount Washington (1916 m) and others. All these massifs are separated by tectonic depressions.
The entire western part of North America, from the Isthmus of Panama in the south to Alaska in the north, as well as the Antilles, is part of the Cordillera, which consists of several “spines” and large plateaus between them. The beginning of the formation of the Cordillera is attributed to the Lower Paleozoic. Most of the “spines” belong to the Mesozoic and Alpine stages of mountain building. Vertical movements, faults and volcanism, as well as anthropogenic icing, played a major role in the relief structure.
The Cordillera in Alaska begins with two main “spines”, which have a latitudinal direction here - the Brooks “spine” in the north and the Alaskan spine in the south. In the Alaskan "spine" there is the highest point of the Cordillera - McKinley (6193 m). The Brooks Mountains have an altitude of 1200-1300 m.
To the north of the Alaskan “spine” there is a large and fairly dissected Yukon plateau with prevailing altitudes of 600-800 m.
From the city of McKinley, the Cordillera returns steeply to the south, continuing in a series of parallel “spines.” Within Canada, their extent is predominantly southeastern. The mountains in this part are quite high, but more dissected by narrow, deep river valleys, and near the coast - by fiords.
The main mountain ranges of the Canadian portion of the Cordillera are the Rocky Mountains in the east and the Coastal "spine" in the west. Between them is the Fraser volcanic plateau, whose height is 800-1200 m.
A system of straits separates the Coastal "spine" from the island chain.
Within the United States, the Cordillera reaches its greatest width (up to 1600 km). They are represented here by large internal plateaus, dissected by deep valleys in which tectonic basins are located (Willamette, California and lower California valleys).
The coastal "spine" of Canada passes into the Cascade Mountains within the United States. The most prominent volcanic peaks here are Rainier (4392 m), Shasta (4316 m) and others. Further south, the Cascade Mountains gradually give way to the Sierra Nevada granite massif with the summit of Whitney (4418 m). Between these “spines” in the west and the Rocky Mountains in the east, lie such huge plateaus as the Columbia, Great Basin and Colorado. The Rocky Mountains within the United States are crowned by a number of high peaks (Elbert - 4399 m, Blanca Peak - 4386 m and others).
In Mexico, the Cordillera is lower and less dissected. Between the Western and Eastern Sierras lies the large Mexican Plateau, the interior of which is an alternation of “spines” and depressions. By the nature of the relief, it resembles the Great Basin. From the south, the plateau is limited by the Transverse Volcanic “spine” with a number of volcanoes (Orizaba - 5700 m, Popocatepetl - 5452 m, Ixtaccituatl and others).
South of the Isthmus of Tehuantepec, the mountain range branches into two parts: one system of mountain ranges deviates to the east and continues on the islands of Central America (Greater and Lesser Antilles), the second - to the Isthmus of Panama.
The Cordillera is characterized by bril and close to horst forms and numerous lacolithic formations. To a lesser extent, they exhibit relief forms predetermined almost exclusively by folding. They are typical mainly for a narrow coastal strip.
Smaller relief features are mostly associated with erosion processes. In the northwestern part of the Cordillera, glacial forms of the terrain are well represented, and in the southeastern part - water-erosive ones. In the interior there are numerous landforms formed by wind activity.
summary of other presentations“Mineral resources of North America” - ATLANTIC OCEAN. Minerals. M A g m a t i c e. Mine development. Mississippian lowland. Relief and minerals. Mexican lowland. Sedimentary rocks. Gold mining. Tectonic map of North America. Appalachian mountains. About gardeners. Colorado Canyon. Relief and minerals of North America. Bingham Copper Mine.
“Characteristics of natural zones of North America” - Soils of Arctic deserts. Indicate the natural zone of North America where the soils are chestnut and chernozem. Features of the placement of natural areas. Tests. Taiga. Natural areas of North America. Taiga plants. Arctic desert climate. Broad-leaved forests. Plants of deciduous forests. Mixed forests. Navigation Guide. Steppes. Animals of the taiga. Desert animals. Plants of Arctic deserts.
"Characteristics of the inland waters of North America" - Source of the Mackenzie River. Rivers flowing from the eastern slopes of the Appalachians. Rivers of North America. Slave Lake. Mississippi. Mississippi with a tributary of the Missouri. Lake Athabasca. Bearish. Niagara River. Inland waters North America. Large rivers. Length. There are many lakes of volcanic origin in the Cordillera. Lakes in the north of the mainland. Most large rivers Pacific Ocean. Great American Lakes. Great Lakes.
“Inland waters of North America” - The largest rivers of the Pacific Ocean are the Columbia and Colorado. Lake Ontario. Huge water system form the Great Lakes. In the north of the mainland is the Mackenzie River. The Columbia River is a beautiful mountain river. Lake Erie is the shallowest of the Great Lakes. Bearish. The Colorado River forms Grand Canyon. Analyze the atlas map and answer the questions. Which ocean basins do the rivers of North America belong to?
“Relief of North America” - Working with a map. Coastal ridges. Get to know the structure and topography of North America. Let's remember. We count and compare. We work with text. Orizaba and Popocatepetl. Cordillera. Geological structure. Let's move on to checking. Differences in mountains Scheme. Sample outline map design. Geological structure and relief. Relief of North America. Relief. Study of relief features. Great Plains. Appalachia.
“Rivers and Lakes of North America” - Managua lake in Central America, in Nicaragua. Area 19.5 thousand km2. Colombia belongs to the Pacific Ocean and is fed by meltwater from glaciers. Michigan is the largest lake within the United States. Lawrence. Depth up to 236 m. The area of its own catchment area is about 90 thousand km2. Erie is a lake in North America, the southernmost in the Great Lakes system. Lake Nicaragua is the largest freshwater body of water in Latin America.
North America. Relief and climate. The third largest continent, with an area of 20.36 million km2– located entirely in the Northern Hemisphere. Northern part The mainland is located far beyond the Arctic Circle, with the tropics in the south. North America is separated from South America by the Panama Canal, and from Eurasia by the Bering Strait.
The shores of North America are washed by the Pacific Ocean in the west, the Arctic Ocean in the north, and the Atlantic Ocean in the east. The coastline is strongly dissected in the northwest, north and northeast. Elements coastline are: bays– Hudson, Mexican, Californian; peninsula– Florida, California, Alaska, Labrador; large islands– Greenland, Newfoundland, Canadian Arctic Archipelago, Greater and Lesser Antilles, Aleutian Islands.
Relief and geological structure.
The continent's topography is diverse and relatively compact, with mountains in the west and southeast and plains in the north and center. Most of the continental plains were formed on ancient North American platform; a vast flat area in the north formed within the Canadian Shield. The northern parts of the plains have pronounced traces of glaciation - hills, ridges. The chain of the Great American Lakes is like the border of the glacier. To the south are the Central Plains, 200-500 m high, formed by continental and marine sediments. To the west of them are the Great Plains, which are a system of plateaus 500-1700 m high, with a flat surface divided by ledges. They are composed of sedimentary rocks of continental and marine origin. South of the Central Plains is located Mississippian lowlands up to 100 m high. This is a flat plain formed by river sediments bordering the coast of the Gulf of Mexico. The Mississippian lowlands are crossed by numerous rivers flowing from the Central and Great Plains, the Appalachians and the Cordillera.
Appalachia, located in the east of the continent, are low folded block mountains (up to 200 m) with wide valleys, plateaus and plateaus. The highest point is Mount Mitchell (2037 m). Distinctive feature mountains - inversion relief, i.e. external structure does not match tectonic structures underlying landforms.
The main mountain system of North America is Cordillera stretches along the western edge of the mainland. Highest point - mountain McKinley(6193 m). This folded belt arose at the junction of two lithospheric plates - oceanic and continental. Active processes of mountain building still continue here: frequent earthquakes and volcanic activity. The largest volcanoes are Orizabo, Katmai. There are two chains of mountain ranges in the Cordillera: the Cordillera proper and the Rocky Mountains. The Cordillera proper is a huge arc bordering an oceanic basin; The ridges and plateaus here are crossed by tectonic faults. In the Rocky Mountains, post-volcanic phenomena are observed in the area Yellowstone national park – geyser eruptions, thermal springs, mud volcanoes. Between the chains of mountain ranges a system of plateaus and highlands is formed: the Yukon Plateau (within Alaska), the Fraser volcanic plateau (within Canada), the Columbia Plateau, the Great Basin, the Colorado Plateau.
Climate.
The diversity of the continent's climate depends on its position at different latitudes. North America is located in all climate zones except the equatorial one. Another important climate-forming factor is the topography of the continent. Meridianally located large mountain systems facilitate the penetration of cold arctic air far to the south and tropical air masses on North. A continental climate is formed in the interior parts of the continent. The climate is also influenced by ocean currents: cold ones - Labrador and California - lower the temperature in the summer, and warm ones - the Gulf Stream and the North Pacific - increase the temperature in the winter and increase the amount of precipitation. However high mountains in the west they impede the penetration of air masses from the Pacific Ocean.
Within arctic climate zone are the northern edge of the mainland and most of the islands of the Arctic Ocean. In winter, temperatures here are very low, snow storms are frequent, and glaciation is widespread. Summer is cold and short, the air warms up to +5 °C. The average annual precipitation is less than 200 mm.
Subarctic climate zone covers the territory between the Arctic Circle and 60° N. w. In the west, the belt extends below the latitude of Moscow. This is due to the influence of the Arctic Ocean, the cold Labrador Current and northeast winds from Greenland. There are oceanic and continental climate types here. In winter, the temperature reaches –30 °C; near the ocean coasts the temperature ranges from –16 to –20 °C. Summer temperatures are 5-10 °C. Precipitation varies from 500 mm per year in the east to 200 mm per year in the west (Alaska region).
Most of the continent is located within temperate climate zone .
It distinguishes three climatic regions:
- region temperate maritime climate in the west of the mainland (the Pacific coast and the western slopes of the Cordillera). Western transport dominates here: winds bring from the ocean a large number of precipitation - up to 3000 mm per year. The average January temperature is up to +4 °C, the average July temperature is up to +16 °C;
- region located in the central part of the belt. It is characterized by relatively warm summers - from +18° to +24 °C; cold winter– down to –20 °C. The amount of precipitation in the west is up to 400 mm, but its amount increases to the east to 700 mm. The almost open space of this part of the continent is subject to the invasion of air masses from both the north and the south. Therefore, atmospheric fronts are frequent here, accompanied by snow storms– in winter and heavy rains – in summer;
- region temperate continental climate distributed on the eastern coast of the Atlantic Ocean. In winter, cyclones are frequent here, bringing a lot of snow; temperatures from –22 °C in the north to –2 °C in the south. Summer is not hot – up to +20 °C; The cold Labrador Current exerts its influence. The amount of precipitation varies, depending on the topography and distance from the ocean, but on average it is 1000-1500 mm per year.
Subtropical climate zone located in the area from 40° N. w. to the Gulf Coast. The territory also has a large extent from west to east, so there are differences in climate types and the following climatic regions are distinguished:
- in the West climate subtropical mediterranean with warm and humid winters: temperature +8 °C, precipitation up to 500 mm per year; and dry, not hot summer: temperature +20 °C - the cold California Current has its influence;
- region subtropical continental climate located in the center of the climate zone. Characterized by high temperatures in summer and low rainfall throughout the year;
- region humid subtropical climate covers the Mississippian lowland. Summer temperatures are up to +30 °C, winters are mild up to +5 °C.
South of 30° N. w. located tropical climate zone , within its borders it is hot all year round. On the east coast of the mainland and on the islands there is a large amount of precipitation brought by the trade winds. The California Peninsula has a dry tropical climate.
Subequatorial climate zone located on the narrowest southern part of the continent. Here, characteristic of this climate zone high temperatures during the year - about +25 °C. Winds from the Pacific and Atlantic Oceans bring a lot of moisture - up to 2000 mm per year.
Sushi waters.
North America has large deep rivers, numerous lakes and significant groundwater reserves. In terms of annual runoff volume, the continent is second only to South America. The river network is unevenly distributed across the continent, and the rivers have Various types nutrition.
Main river system of the mainland Mississippi with influx Missouri has a length of 6420 km, and carries its waters to the Gulf of Mexico. The river basin includes the Rocky Mountains, Appalachians, Central and Great Plains. The river is full-flowing all year round and has snow and rain types of feeding. The rivers of the Pacific Ocean basin have a steep fall, so they are turbulent and rich in hydropower. Among them are large rivers Colorado(2740 km) and Colombia(2250 km). River Yukon in northwestern Alaska it is full of water in the summer, during the snowmelt period. The largest river in the Arctic Ocean basin Mackenzie 4250 km long, it originates in Great Slave Lake.
Most of the lakes in North America are located in areas that were subject to glaciation. The most unique system Great Lakes– Superior, Huron, Michigan, Erie, Ontario – the world's largest clusters fresh water on the land. Most lakes have significant depth, for example, Lake Superior is almost 400 m deep. Lakes Erie and Lake Ontario are connected by the Niagara River. Cutting through a hilly ridge, the river falls into the Niagara Falls, 50 m high and 1 km wide.
The largest lakes in North America are also Winnipeg, Great Slave, Great Bear, Athabasca. Residual lakes are preserved in the Great Basin Basin - Great Salt, Utah.
Lesson summary “North America. Relief and climate".
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North America. Relief and climate
5 (100%) 3 votesGeological structure of North America
At the base North America and most of Greenland lies Precambrian North American Platform, which is sometimes called Canadian. The foundation of the platform in some places faces surface, forming Canadian-Granland Shield. The shield formed by faults consists of metamorphosed volcanic rocks and granite gneisses of Archean and early Proterozoic age. Grenville belt, which stretches in the southeastern part shield, formed by Early Precambrian rocks and metamorphosed Proterozoic carbonate-clastic formations.
As geophysical studies and drilling data show, the foundation, covered with a sedimentary cover, is also composed of Early Precambrian metamorphosed sedimentary-volcanic rocks and granite-gneisses. In the building Rocky Mountains USA is being viewed early Precambrian crystalline rocks. Sedimentary cover platforms extend to the south, west and north of the Canadian Shield, and its greatest area observed in the area Midcontinent and Great Plains. The depth of the foundation changes, so a number of large depressions – syneclise, with a depth of $3$-$4$ km and vaults – anteclise. Part of the platform in the southwest cuts mobile zone mountains Ouachita.
In the meridional strip Great Plains continued in the Mesozoic subsidence and accumulation coastal-marine and continental sediments. Finally, marine sediments were replaced by continental sediments at the beginning Cenozoic era, and after this came complete platform drainage.
Paleozoic cover platforms in addition to the Midcontinent and the Great Plains also extends to Arctic its slope. Here it forms the southern part of the Canadian Arctic Archipelago. Shallow but large syneclise Hudson Bay is filled with formations that are similar in composition and age. Its central part is composed thin continental sediments Jurassic and Cretaceous.
Caledonides Northeast Greenland are the most ancient link folded frame of the North American platform. In the form of tectonic nappes, they are thrust onto the edge of the platform and are composed of a thick layer of sedimentary terrigenous-carbonate rocks of the Lower Paleozoic. Along the fault, the so-called Logan line, the fold system of the island of Newfoundland and the Northern Appalachians border the Canadian Shield.
Line Logan represents thrust geosynclinal Paleozoic strata into the platform Paleozoic and Precambrian. Narrow grabens with continental sediments and basaltic lavas there are also Northern and Southern Appalachia. This is evidence that before entering the platform stage of development, the Appalachian system was fragmented.
Zone Hercynian folding within the coastal lowlands - from the Gulf of Mexico - blocked by powerful Cenozoic deposits. System Canadian Arctic Archipelago and north Greenland related to Hercynian folding, composed of Cambrian-Devonian terrigenous-carbonate deposits.
folded Cordillera belt, located along the Pacific coast, borders almost the entire length with North American platform, with the exception of Alaska. Here this belt is limited by the ridge system Brooks. The main seismically active North American zone.
Note 1
The zone is characterized by destructive earthquakes– Alaskan ($1964), Mexican ($1985), San Francisco ($1906). In the future this zone still remains earthquake-prone, especially in those places where it intersects with latitudinal transform faults of the Pacific Ocean.
Relief of North America
The relief of North America is characterized by a fairly large variety and contrast.
Almost replaced flat plains in the central part of the continent there are vast hilly expanses, neighboring in the east with low Appalachia.
In the west, the Central Plains are adjacent to Cordilleras. The peaks of these mountain structures are sharp and reach a height of more than $6000$ m. The relief of the continent and its features are associated with the history of the geological development of the territory. Ancient The North American Plate and its crystalline basement formed throughout Archean and Proterozoic eras. Canadian crystal shield in relief corresponds Laurentian elevation.
On stove, located south of the Canadian Shield, are Central and Great Plains. The Great Plains stretch from north to south for $3,500 km and are located in the western part of the platform. Their height reaches $1500$ m, which can be explained by powerful uplifts of the earth’s crust in the area of the Cordilleran folding.
South of Laurentian the hills are located Central Plains. In the south of the mainland are Sub-Mexican and Atlantic lowlands formed on the foundation of a young platform covered with sedimentary deposits. Appalachia are old, eroded mountains, with flattened and low ridges. Folding in them occurred during the Caledonian and Hercynian periods.
In the west of the continent, grandiose folding began in Mesozoic era as a result of the collision of lithospheric plates and continues to this day. Originated here Cordillera stretched in the meridional direction for $9000$ km, with a width of $1600$ km.
The mountains do not end in the south of the continent, but continue in South America. The summit of the Cordillera is Mt. McKinley, whose height is $6193$ m. Numerous faults in the bottom of the Pacific Ocean continue in the Cordillera ridges. The mountains are characterized by the largest volcanoes planets - Popocatepetl and Orizaba.
Note 2
Not only internal, but also external processes took part in the formation of the relief. The northern regions of the mainland up to $40$ parallels were covered glacier, which in size exceeded the area of Australia by $2$ times. The movement of the glacier leveled the surface and even polished the rocks. The glacier created thousands of hills of great extent and many small landforms.
In addition to the glacier, they took an active part in the formation of the relief superficial, The groundwater and wind. For example, the work of a river Colorado created Grand Canyon, the depth of which is $1600$ m, and the length is $400$ km. The largest on the planet Mamontov the cave was formed underground water, and activity wind led to the emergence of dunes, dunes and other forms of relief.
Mainland minerals
Subsoil of North America rich in minerals and are related to its geological structure. The largest in the world ore deposits occur in the area Canadian Crystal Shield, where igneous and metamorphic rocks are found shallow. The largest deposits are concentrated here iron, nickel, copper, uranium, molybdenum.
Coal located in a thick layer of sedimentary rocks Central Plains, and coastal lowlands and shelf seas have large sediments oil and gas. Hydrocarbon production is carried out both on land and from Mexican bay. The intermontane depressions of the Appalachians also have significant reserves stone coal
IN Cordillera large deposits of minerals of both igneous and sedimentary origin are concentrated. There is non-ferrous metal ores, gold, mercury. In the east and in the trough of the earth's crust between Cordilleras and the North American Plate lie oil, gas, coal. Significant reserves and diverse mineral resources are an important natural raw material base for the economic development of countries located on this continent.
Relief of North America mainly flat, because most of it lies within platforms. The western and eastern parts of the continent were formed at different geological times - western Part in the Mesozoic and Cenozoic, A eastern part - in Paleozoic.
Note 3
The ancient and ruined Appalachians are located in the east of the continent, and the high and young Cordilleras are located in the west. Associated with the peculiarities of the geological structure richness and variety mineral resources of the mainland. And such minerals as coal, oil, natural gas, iron, nickel, molybdenum ores and uranium have global significance.
The landscape of North America was formed by a variety of geological processes. Some of them continue to this day. What are the features of the relief and its specificity - the material presented will help answer these questions.
Relief of North America
The relief of North America is diverse and contrasting. The continent lies on the lithospheric plates - North American and Caribbean. The western boundary of the last plate passes through Eurasia.
The central region has flat plains interspersed with vast expanses of hilly terrain. In the east they are adjacent to the Appalachian Mountains. In the west, the plains are adjacent to the Cordillera mountain ranges.
The relief features of North America are determined by the specific geological development of the territory, which is 4.5 billion years old.
Rice. 1. Relief map of North America
The peculiar foundation of the continent is the ancient North American Plateau, whose relief is expressed by plains of varying heights, the shapes and outlines of which resemble waves.
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They played a central role in the formation of the relief. external processes. Many millennia ago, the areas located in the northern part of the continent were a glacier.
The glacier that existed at that time was twice the size of Australia, and its power was such that this giant easily polished the surface of rocks and leveled the ground beneath it.
The formation of the landscape was influenced by the following factors:
- impact of surface and groundwater;
- wind.
Relief structure of North America
The structure of the continental surface is divided into the following parts: northern and central, where the plains are located, eastern - with the Appalachian mountains, and western - with the Cordillera. This is the largest mountain system in the world.
In the northwestern part of the continent, large landforms of North America are represented by mountain ranges that reach maximum heights. Mount McKinley located here (6193 m.) - highest point Cordilleras and North America.
Rice. 2. Mount McKinley
Together with the South American Andes, these heights make up the longest mountain chain in the world - over 18 thousand km!
Mountain building in the Cordillera occurs continuously. This is indicated by the constant activity of volcanoes, which is accompanied by frequent earthquakes. The active volcanoes here are:
- Orizaba (5700 m);
- Popocatepetl (5452 m);
- Colima (3846 m).
Seismically active areas of the continent are located on the western and Pacific coasts.
Rice. 3. Vulcan
The plains were formed on tectonic plates and occupy two-thirds of the surface. To the south of the Laurentian Upland stretch the Central Plains with average heights of 200-300 m. To the west of the Central Plains along the Cordillera, the Great Plains stretch in a strip. The surface is dotted with river valleys and ledges into separate massifs and plateaus.
To understand the relief of North America, you need to have an idea of the processes affecting the surface of the platform, which has been destroyed and leveled many times.
What have we learned?
From an article on geography (7th grade), we learned what factors influenced the relief features of North America. What natural processes occur in this area. What part of the continent is occupied by mountains and what part is plains. Why mountain building is a constant and continuous cycle. It was also possible to obtain information about the age of the territory on which the mainland is located. It was possible to find out what explains the diversity and contrast of the relief characteristic of this territory. We have clarified the location highest peak Cordilleras and North America.
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