The orography of South America shows some similarities with North America. On east, off the coast of the Atlantic Ocean there are vast highlands: Brazilian, Guiana and Patagonian. In the extreme west and north of the continent, repeating the contours of its coasts, stretches for 9 thousand km the longest mountain system in the world - the Andes, or South American Cordillera. Between the highlands and the Andes there are vast low-lying plains, occupying approximately 45% of the continent's territory: the Amazonian, Orinoco and Paraguayan-Paran. They are irrigated by the largest rivers of America and are all connected to each other, forming a continuous strip of plains in the middle part of the continent.
The large, eastern part of the mainland is a platform. In the north and west it is bordered by a zone of buildings.
The foundation of the South American platform for the most part Precambrian age, and in the south - Hercynian. On this basis, on modern tectonic maps of the South, the Guiano-Brazilian (South American) platform is distinguished on the Archean-Proterozoic folded foundation and the Patagonian platform on the Hercynian foundation. The development of platform structures in South America obviously occurred in close connection with the platforms of other continents of the southern hemisphere - Africa, Australia, Antarctica and South Asia. The structure of the platform is characterized by the presence of protrusions of the ancient foundation and depressions in which the ancient folded foundation is hidden under layers of younger sedimentary deposits. Protrusions in the relief usually correspond to the highlands of the eastern part of the continent, and depressions - lowlands. However, there is no complete coincidence of structure and relief.
Precambrian orogenic cycles covered large parts of South America. Maybe, What in the Precambrian there was a connection between all the continents of the southern hemisphere. At the same time, extensive geosynclinal basins were formed, one of which was the Andean basin. geosynclines, continued on north of the Cordilleran geosyncline of North America.
In the Cambrian, a significant depression occurred in the Amazon Lowland, which then spread into the Paraguay basin. The sea occupied large spaces on the platform in the Devonian, and in the Carboniferous period its area decreased again. Obviously, in the southern part of the mainland, approximately south of 37° S. sh., from the beginning of the Paleozoic there was a trough of a geosynclinal type, mountain building in which occurred during the Hercynian cycle, What led to the creation of the Patagonian Platform. These folded structures (Gondwanids) were articulated from the south To Precambrian platform, forming a single whole with it. The Precambrian base of the platform underwent splits during the Hercynian cycle, which in the southern part of the Brazilian salient were accompanied by powerful outpourings of magma. Manifestation the Hercynian orogeny was also V within the Andean geosyncline, and mountain building captured its eastern margin adjacent to the platform.
Throughout the Paleozoic, the huge continent of the southern hemisphere, Gondwanaland, continued to exist as a single whole. At the end of the Carboniferous and in the Permian, in connection with the completion of the Hercynian folding and the general uplift of the land, there was continental glaciation on Gondwana. This is evidenced by the finds of ancient moraine in the southern part of the Brazilian Highlands, as well as in Africa and Australia.
In the Triassic, a trough formed in place of the South Atlantic Ocean, and Gondwana began to break up.
On the platform during the Mesozoic, the previously formed mountains were destroyed and large masses of continental sediments accumulated, which gradually filled the trough areas, turning them into dry land.
In the Lower Cretaceous, orogenesis began within the Andean geosyncline, first covering its western regions and accompanied by intense volcanic processes. In the Tertiary period, mountain building spread into the eastern parts of the geosynclinal region, and in the Pliocene the Coastal Cordillera was formed and the final connection between the two American continents occurred. The edge of the platform was also captured by mountain building processes, as a result of which highly modified sections of Precambrian and Upper Paleozoic structures were added to the Andean system.
At the end of the Tertiary and at the beginning of the Quaternary period, the entire Andean system was covered by differentiated vertical movements, faults And volcanism.
Descents at the end of the tertiary period caused the subsidence of a large part of the western edge of the Andes. The modern Andes represent only the eastern marginal part of the folded zone, while its main part is submerged under the waters of the Pacific Ocean. The vertical movements that resulted in the uplift of the rest of the Andes led to increased denudation and the formation of a series of planation surfaces and a system of steps that are a distinctive feature of the Andean topography. Volcanism and seismicity as evidence of unfinished processes mountain building, are characteristic of the Andes even today. The final phases of the orogenic cycle also affected the entire platform part of South America. They manifested themselves in the formation of faults, accompanied by outpourings of lavas, uplift and subsidence of individual sections and associated With this revitalizes the processes of erosion and denudation.
During the Quaternary period, the Andes underwent mountain glaciation. In some places, glaciers extended beyond the mountainous country, as evidenced by the accumulation of loess-like deposits on the adjacent plains between the 30th and 40th parallels.
The following large structural and morphological areas are distinguished on the territory of South America:
Brazilian Highlands - the most extensive uplift V within the platform. It extends in the eastern part of the continent from 4 to 30° S. w. Most of the highland corresponds to a protrusion on the surface of the folded base of the platform, welded together from Archean and Proterozoic folds. But in the center of the highlands, the crystalline basement is deeply depressed and overlain by horizontally lying but highly elevated Mesozoic sediments. Thus, the interior of the highland is a depression in the folded base of the platform.
The eastern and southeastern margins of the massif, facing directly to the Atlantic Ocean, are uplifted by faults and are strongly dissected. They fall into a series of ridges reaching more than 2000 m in height. These ridges, rising high above ocean or over a narrow coastal plain, they descend gradually towards the center of the highlands, turning into an undulating peneplain surface with an average height of 600- 800 m. The southeastern edge of the highlands comes close to the coast in the area of Rio de Janeiro, where a strongly dissected coast, accompanied by small islands, indicates recent subsidence of the land. To the north and south of this area, the Brazilian Highlands retreat from the ocean, separated from it by a young sandy plain with a lagoonal coast.
The interior of the highland, composed of sedimentary rocks, consists of a series of table plateaus with steep slopes. To the north-west and north the highlands noticeably decrease towards the adjacent low-lying plains.
The edges of the highlands in these places, and the presence of crystalline rocks noted numerous rapids and waterfalls that abound in the tributaries of the Amazon flowing from the Brazilian Highlands.
In the north of the continent, a vast protrusion of the folded base of the South American platform corresponds in the relief of the Guiana Highlands.
The central part of the highlands is the highest and most dissected, between the valleys of the Upper Orinoco and Essequibo rivers. Individual ridges, crowned by strata of dense sandstones, reach 1000-1500 m, and the highest massif exceeds 2500 m. The eastern part of the highlands is a hilly crystalline plateau with an elevated southern edge.
The western part of the Guiana salient is not orographically connected with the rest of the highlands, but is separated from it by the Orinoco lowland. This is the Pardaos massif adjacent to the Andes, within whom crystalline rocks covered in thicknesses Cretaceous and Tertiary deposits and are exposed only in the deepest valleys.
In the extreme southeast of the continent, on the Patagonian Plateau, the base of the platform is formed by structures of Hercynian age. In the northern part they protrude to the surface, and to the south they are covered with Cretaceous sedimentary deposits and volcanic rocks. The surface of the plateau is small dismembered, because due to the dry climate there almost there are no watercourses. The plateau, reaching 1500 m in height, approaches the very shore of the Atlantic Ocean and drops down to it in hundred-meter steps.
On both sides of 30° S. w. there is a section of the platform that was subjected to late tertiary uplifts in connection with mountain building within the Andean geosynclines. Currently, meridional blocky ridges rise there, composed of crystalline rocks and reaching heights from 2000 to 6000 m. Between the ridges there are depressions filled with continental sediments. The ranges called the Pampine Sierras and the Precordillera are part of the Andes system.
The most extensive lowland in South America - Amazonian- one of the largest on the globe, formed on the site of an ancient extensive trough within the platform. It is located between the Andes, the Brazilian and Guiana Highlands. The folded foundation is buried to a depth of many thousands of meters. In the western part the surface of the lowland is almost ideal flat. To the east, that is, downstream of the Amazon, the Guiana and Brazilian highlands come closer together and the alluvial lowland remains only in the form of a wide strip along the course of the Amazon. To the south and north of the valley, the crystalline foundation of the platform lies close to surfaces and is exposed by the deep valleys of the Amazon tributaries.
In the trough between the Guiana Highlands and the Andes there is the Orinoco Lowland, filled with marine Tertiary sediments and continental sediments carried down from the neighboring mountains. Its western part is lower and flat, the eastern part is elevated and dissected by deep river valleys on a plateau 200-300 m high. When the Orinoco flows into the Atlantic Ocean, a flat, swampy delta plain with traces recent drops.
In the basin of the Parana, Paraguay and Uruguay rivers, in the zone of the platform trough between the Brazilian Highlands and the Andes, the Gran Chaco plain and the La Plata lowland are located.
In the northwestern part, in the Gran Chaco, heights reach 600-800 m, and the dissected surface folded continental tertiary sediments. To the south the surface decreases. It is covered by strata of Quaternary alluvial, fluvioglacial and loess-like sediments, under which more ancient continental strata are hidden, reaching great thickness. South of La Plata, within that part of the lowland called the Pampa, isolated hills rise. They represent projections of Precambrian and Paleozoic platform structures and are called the Sierras of Buenos Aires.
The north and west of the mainland is occupied by the complex Andean system, diverse both tectonically and morphologically. In the structure of the mountain system, a number of parallel orographic zones are distinguished, replacing each other from the Pacific Ocean inland: low plateau-like ridges of the Coastal Cordillera stretch along the coast of the Pacific Ocean and along the islands. On the larger parts The coasts of the mountains drop steeply to the ocean, forming an undivided longitudinal tectonic coast.
The coastal Cordillera does not form a continuous strip. They appear at the extreme northern section of the coast as a continuation of the mountains of Central America, then break off and continue again only to 20° S. w. In the far south due to With With recent subsidence, the marginal zone of the Andes experienced fragmentation and turned into islands located in close proximity to the mainland.
The main part of the mountain system consists of structures of Mesozoic-Tertiary age. Extinct volcanic rocks play a major role in the structure of mountains. And active volcanoes. The most important areas of modern and recent volcanism are located in the Andes on both sides of the equator in Ecuador, south of 30° S. w. within Chile and in the central part of the mainland between 13 and 29 ° S. w.
The Andes ridges, called the Cordillera, stretch in parallel chains or fan out. In the middle part of the mountain system between the Cordilleras there are vast flat areas cluttered with debris and products of volcanic eruptions. They're called Andean plateaus or Poonami. Their heights are 3500-4500 m, while in the Cordillera individual peaks rise to 6000 and even 7000 m. The high Cordilleras of the Andes are distinguished by a typical alpine topography, with mountain-glacial forms and modern glaciers.
In the southeast of the continent at parallel 40° S. w. The Hercynian structures of the Natagonian platform, the so-called “Patagonids”, reworked by Mesozoic uplifts, are attached to the Andes in the form of blocky ridges.
The mineral resources of South America have been very unevenly explored. But what is already known testifies to the enormous wealth of the continent in various mineral resources. The deposits of various metal ores associated with How with the oldest crystalline rocks of the platform basement, and with the processes of volcanism that occurred in the Andean geosynclinal region. But the mainland also has large mineral reserves sedimentary origin.
The richest reserves of metal ores are concentrated in the Andes, mainly in their central part. These ore deposits were formed during the formation of the Andes in communications with the processes of volcanism and contact metamorphism. Bolivia has deposits of tin, tungsten, antimony, lead, zinc and silver. In Peru, polymetallic ores containing copper, lead, zinc and gold are common in the territory Colombia- reserves of gold and platinum. Chile is rich in copper and has one of the largest copper deposits on the globe, formed in connection with the processes of Tertiary volcanism. Moreover, on average Chile there are large deposits of radioactive elements. With processes volcanism in the Andes connected sulfur deposits.
In the Brazilian and Guiana Highlands, there are deposits of iron ore in the Algoncan shales and conglomerates (the largest of them are in the southeast of the Brazilian Highlands and on the northern slope of the Guiana Highlands). Manganese ores formed as a result of weathering of ancient crystalline rocks occur in approximately the same areas.
Numerous gold deposits are associated with ancient intrusions and metamorphic processes, occurring on the southeastern edge of the Brazilian Highlands and in the northeastern Guiana Highlands. The destruction products of ancient pegmatite veins contain radioactive elements and diamonds.
In the Guiana, and partly in the Brazilian highlands, there are large deposits of bauxite, formed as a result of lateritic weathering of acidic and alkaline rocks of an ancient crystalline base.
The entire area between the Andes and the Brazilian Highlands, the intermountain basins and the coastal zone of the Andes are rich in oil. Especially big its reserves are concentrated in Venezuela around the Maracaibo lagoon and in the Caribbean Andes, as well as in Colombia, in the valley of the Magdalena and Cauca rivers. Relatively recently, oil was discovered within the platform - in Patagonia, in the Amazonian lowland and in the Brazilian Highlands.
On the Pacific coast ocean, in the Atacame Desert and on the coastal islands there are the world's only deposits of natural nitrate. It is a product of the decomposition of organic residues accumulated under dry and hot climate conditions in previous geological periods.
The process of formation of valuable organic substances (guano), used as fertilizer, occurs on the coastal islands of the Pacific Ocean at the present time. The material for this is organic remains accumulated by birds nesting there.
Features of the geological structure of South America
Millions of years ago there was an ancient supercontinent Gondwana . It broke up into three large blocks of lithosphere, which formed the basis of four modern continents: Africa, Australia, Antarctica and South America . The latter will be discussed in this article.
In the geological structure of South America, a clear difference between the eastern and central parts and the western part of the continent is clearly visible. The east and center of the continent are located on the old Precambrian South American platform . In the north and east of the platform there are extensive areas where the ancient crystalline foundation of the platform comes to the surface - Guiana and Brazilian shields . The western part of the continent is represented folded area , formed as a result of the collision of a continental platform and an oceanic lithospheric plate.
The oceanic plate bends and moves under the continental plate, forming a deep Peruvian trough (trench) along the entire west coast.
The edge of the continental plate is folded. Mountains rose along the entire western edge of the continent. This is a young area - Cenozoic folding . This is evidenced by volcanic eruptions and frequent earthquakes. There is an active process of mountain building. The west coast of South America is part of "Pacific Ring of Fire" – areas of active seismic activity.
The platform part of the continent has experienced repeated subsidence and uplift in the past. This is evidenced by sedimentary rock deposits, including marine sediments.
Currently, the platform part of the continent is dominated by erosion processes, enhanced by human economic activity.
Relief features of South America
The folded region in western South America forms one of the largest mountain systems on the planet - Andes mountains . In Indian language this means "copper mountains" .
The Andes Mountains stretch along the Pacific coast in three parallel mountain ranges. Many peaks rise above $6000$ m above sea level.
Highest point in South America Aconcagua ($6960 m).
At the same time, it is the highest point of the entire Western Hemisphere.
There are also many active volcanoes here. The most famous of them are Cotopaxi, Ruiz, San Pedro . In the middle part of the mountain system there are internal plateaus, the heights of which reach $3500-4000 $ m. The platform areas of South America are represented by plains - lowlands and plateaus.
Definition 1
Lowland – this is a section of plain with absolute heights up to $200$ m.
Definition 2
Plateau – this is a section of plain with absolute heights of more than $500$ m.
The lowlands of South America are Orinoco, Amazonian and La Plata . The elevation difference here is insignificant. These are almost flat plains.
Note 1
Amazonian lowland - the largest lowland in area on the globe.
Thanks to marine sediments, the northern parts of the plains are rich in oil. Formed on crystalline shields Brazilian and Guiana plateaus . As a result of ancient tectonic activity, the lowering and raising of the platform was accompanied by faults in the earth's crust and lava outcrops. In some places, the relief of the plateaus has the appearance of table mountains. They are replaced by landscapes of hilly plains, low massifs, cut by gorges.
Minerals
The distribution of minerals is also related to the geological structure.
- Deposits are located on ancient shields iron, manganese, uranium ores, bauxite, diamonds.
- The Andes, true to their name, are famous copper ores, deposits gold.
- Large deposits discovered in the north of the continent oil.
- On the deserted western coast, due to the climate, deposits were formed sodium nitrate.
The center of the continent (Amazonian lowland) is still poorly studied and developed.
The relief of South America is varied and contrasting. Based on the nature of the surface structure on the continent, two parts are distinguished. The greater eastern part is dominated by lowland, elevated plains and plateaus, while the longest mountain ranges of the Andes are in the west.
The lowland plains (Amazonian, Orinoco, La Plata) have a flat topography and are composed of marine and lacustrine-fluvial deposits. The relief of the western part of the continent is the result of the interaction of several lithospheric plates, on the border of which mountain-building movements occur.
The formation of the Andes began in the Paleozoic and has not ended yet. The Andes continue to rise, volcanoes erupt, and strong earthquakes occur.
South America is rich in mineral deposits. The ancient shields of the platform contain the richest deposits of iron, manganese, nickel ores, uranium, and deposits of bauxite containing aluminum. Oil, natural gas, and coal were discovered in the depressions and troughs of the platform. Deposits of non-ferrous and rare metals have been found in the Andes. For example, the famous “tin belt” of Bolivia stretches from north to south for 940 km. The Andes are home to the world's largest deposits of copper ores, as well as molybdenum, silver, tungsten, lead and zinc ores. Sulfur, boron, iodine, and saltpeter are mined from non-metallic minerals on the Pacific coast and in the foothills of the Andes. There is oil in the intermountain basins.
South America is made up of two main geological elements: the Andes, a folded mountain belt in the east, and the South American mountain platform. Throughout its existence, the platform has been lowered and raised several times. Sedimentary rocks accumulated in the subsided areas, and crystalline rocks in the uplifted areas. Due to the different rates of uplift, the earth's crust cracked and lava splashed to the surface.
The continent, due to the peculiarities of its internal structure, can be divided into two parts:
1. Vast lowlands.
Landforms of South America
La Plata, Orinokska and Amazonian lowlands, located in the troughs of the South American platform, occupy almost half the area of the continent.
2. Plateaus. In the east Guiana and the Brazilian plateau are formed by projections of the basement. In some places their height reaches 3000 m. The plateaus on the mainland are dotted with numerous river valleys, which can be seen if you look video in English.
central part Guiana The plateau is notable for its huge flat-topped massifs, the walls of which are almost vertical. It is cut by abysses and deep canyons, but from a great height it seems that the surface is absolutely flat.
The Andes mountain system stretches along the Pacific coast, the average heights of which range from 3000 to 5000 m. The highest point is Mount Aconcagua (6960 m). These are young mountains, strong earthquakes and volcanisms are occurring here and now, resulting in the formation of the San Pedro and Cotopaxi.
Gold, uranium, aluminum, manganese, and iron ore are mined on the Guiana and Brazilian plateaus. The Andes are home to deposits of precious stones, zinc, lead and copper ores.
Thanks to the arid climate in the west of the South American continent, deposits of Chilean sulfur, which is a raw material for nitrogen fertilizer and iodine, have formed in dry reservoirs.
Volcanic phenomena in Andes contributed to the formation of deposits of building materials and sulfur. In the foothills and troughs of the platform in sedimentary deposits there are deposits of gas, oil, and coal. The largest oil fields are concentrated on the coast of the Caspian Sea and in the foothills of the Andes.
South America. PHYSICAL AND GEOGRAPHICAL POSITION.
The area of the mainland is 17.8 million sq. km without islands and 18.3 million sq. km with islands. Extent from north to south -70 degrees. w.d. exceeds 7500 km, from west to east (in the widest part) more than 45oo km. South America in the northern part is crossed by the equator. The northernmost point is Cape Galinhas, 13 deg. N; southernmost continental point Cape Froward, 54 deg. S, Cape Horn island, 56 deg. S The continent lies entirely in the Western Hemisphere. Westernmost point Cape Parinhas, 81 deg. w.d.; easternmost point Cape Cabo Branco, 34 deg. w.d.
South America lies in the equatorial, two subequatorial, two tropical climate zones; the southern part is located in the subtropics and temperate zone.
The continent is connected to North America by the Isthmus of Panama and separated from it by the Panama Canal, and from Antarctica by the Drake Passage.
Geological structure and main landforms of South America
It is washed in the west by the Pacific Ocean, in the south by the Drake Irrigation, in the east by the Atlantic Ocean, and in the north by the Caribbean Sea of the Atlantic Ocean. In the north there is the warm North Trade Wind Current, in the northeast - the warm Guiana Current, in the east - the warm Brazilian Current, in the southeast - the cold Falkland Current, in the south - the cold West Wind Current, in the west - the cold Peruvian Current, in the north -west - warm El Niño current. The coastline is slightly indented. Small bays are located at the mouths of rivers (La Plata, Maracaibo). Adjacent islands: in the north - the Lesser Antilles, in the southeast - the Falklands (Malvinas), in the south - Tierra del Fuego, in the southwest - the Chilean archipelago. The geographical position of the continent, mainly in low latitudes, determines the predominance of tropical types of landscapes - the “kingdom of tropical nature”.
TECTONIC STRUCTURE, RELIEF, MINERAL RESOURCES.
The relief of South America is asymmetrical. Most of the continent is occupied by vast plains of varying altitudes. In the west is one of the highest mountain systems in the world - the South American Cordillera (Andes). The average height of the continent is 580 m, the highest point is Mount Aconcagua 6960 m, the lowest is the Valdes Peninsula - 40 m. The relief features are determined by the tectonic structure. At the base of South America lies the ancient South American Platform with a Precambrian basement. Within the platform there are large shields in the north and east, which correspond to the Guiana and Brazilian plateaus. Powerful block processes occurred within the Guiana Plateau, which is why the plateau has a highly dissected topography. The highest point is Mount Roraima 2771 m, average heights range from 500 to 1000 m.
The Brazilian plateau corresponds to three shields: Southern Amazonian, Eastern Brazilian, Western Brazilian. This plateau rises gently from the north and northwest to the southeast. The highest point is Mount Bandeira 2890 m. Active magmatism occurred within this territory, traps and volcanic plateaus are found here. This territory is finished
its formation. Peneplains (leveling surfaces, denudation plains) are formed here.
Between the shields there are syneclises (deflections) of the platform foundation, which are filled with thick layers of sedimentary rocks. They correspond to the vast lowland plains of South America: Amazonian, La Plata, Orinoco.
In the west, the platform is adjacent to an area of folding of Alpine age, which was formed in the Cenozoic as a result of the subduction of the Nazca plate and the South American lithospheric plate. This area of folding corresponds to the Andes, which belong to the highest and highest mountains. The highest point is Mount Aconcagua 6960 m. Mountain building processes here have not yet been completed and are accompanied by earthquakes and volcanism (volcanoes Cotopaxi, Chimborazo). Tectonic processes are strong in the Caribbean, Northern and Southern Andes, calm in the Central and Patagonian Andes. The Andes are made up of parallel ridges. As they come closer, they form mountain nodes, and where the ridges diverge lie the Central Andean highlands and plateaus with an altitude of 3500-4000m.
South America has a huge mineral resource base. Ore deposits are confined to outcrops of the crystalline basement and to the Andean fold belt. Non-metallic - to the cover of sedimentary rocks of the platform. Significant deposits of iron (Minas Geras - Brazil), manganese, bauxite, titanium and uranium ores were formed in ancient igneous and metamorphic rocks and weathering crusts. Reserves of beryllium, niobium, zirconium, and tantalum are concentrated here. Vein deposits of gold and diamonds in Brazil play a significant role. On the Guiana Plateau there are large deposits of iron ore, bauxite and gold; large reserves of copper are concentrated in the Andean belt in Peru and Chile; in Bolivia there is a tin belt. Emeralds are mined in Colombia. In the sedimentary cover of the Orinoco, Amazon and La Plata lowlands there are oil deposits, especially in Venezuela. 99% of the world's saltpeter reserves are concentrated in Atacama.
South America is the wettest continent on Earth, but not as hot as Africa, since the southern part lies in the temperate zone. Within the continent, an equatorial, two subequatorial, and two tropical climatic zones are formed; the southern part lies in the subtropics and temperate zone.
In general, the climate of South America is more varied than that of Africa and Australia. Average annual temperatures in most of the continent are from +20 to +28, and only in the south are these figures lower (from +8 in winter to + 16 in summer). The maximum recorded temperature is +46 (Cordoba), the minimum is -33 (Sariento). Antarctica has a huge influence on the climate of South America, from which the cold pampero wind blows into the temperate and even subtropical zones. In Patagonia, temperatures can drop to 0 in summer and -30 in winter; in the subtropics in the south of the Brazilian Plateau in summer up to +15, in winter up to +8.
The distribution of precipitation is extremely uneven, but the size of the precipitation layer is enormous - on average 1700 mm. The drainage layer into the hydrographic network is 700 mm. These values are twice the earth's average. Maximum
the amount of precipitation falls in the western part of the Amazonian lowland (3000-4000 mm), on the western slopes of the equatorial Andes (up to 7000 mm) and on the western slopes of the Patagonian Andes (up to 4000-5000 mm). The minimum amount of precipitation is in the inland areas of the tropical zone, the south of the La Plata Lowland, and the barrier rain shadow zone in Patagonia. In general, the climate of South America, which is characterized by an abundance of warmth and light over most of the territory, creates favorable conditions for year-round plant growth.
INLAND WATERS.
Since South America is the wettest continent on Earth, one of the largest hydrographic networks in the world has formed here. South America covers 12% of the world's land area, but accounts for 36% of the world's ocean flow, 15% of which comes from the Amazon. The pattern of the hydrographic network is extremely asymmetrical, which is determined by the features of the relief. The main watershed runs along the tops of the Andes near the Pacific Ocean, so all the major rivers belong to the Atlantic Ocean basin (Amazon, Parana, Orinoco, San Francisco). Most of the rivers are fed by rain, and only the rivers of Patagonia and the Patagonian Andes are fed by snow and glaciers. The regime of rivers is determined by their position in climatic zones. For example, the rivers of the Amazon basin, which are fed by rain, are full of water throughout the year with two maximums in spring and autumn during the period of zenithal rains. Rivers of the subequatorial type are also fed by rain. These are major tributaries of the Amazon, Orinoco and Paraguay Rivers. They have maximum flow at the end of summer, beginning of autumn and winter low water. The rivers of the tropical zone in inland areas are low-water, but in the southeast of the Brazilian Plateau they are full-flowing throughout the year. Most of the rivers in the upper reaches are mountainous in nature, as they begin in the Andes and on the plateaus. There are an abundance of rapids and waterfalls. On the Guiana Plateau is the world's highest Angel Falls (1054 m). On the Iguazu River (Brazilian Plateau) is the world's longest Iguazu Falls (length about 3000 m, includes more than 270 cascades).
There are few large lakes. In the southern part of the Andes there are glacial lakes, in the north there is the lake-lagoon Maracaibo of tectonic origin, in the Central Andes at an altitude of 3800 m lies the largest alpine lake Titicaca with depths of up to 300 m.
Modern glaciation is relatively weak due to the high position of the snow line. Maximum glaciation in the Patagonian Andes and Tierra del Fuego.
NATURAL AREAS.
Due to its large extent from north to south, the continent has a clearly represented natural zonation from equatorial forests in the center to semi-deserts and temperate deserts in the south. Due to the predominance of a hot, humid climate on the mainland, forests are widespread here and there are relatively few deserts and semi-deserts.
1) The zone of moist equatorial forests (selva) is located on both sides of the equator in the Amazon basin, on the slopes of the Andes and in the north of the Pacific coast. The zone is formed within the equatorial and subequatorial climatic zones. Thanks to the processes of chemical weathering, fertile red-yellow ferralite soils are formed in the jungle. Various types of palm trees, cocoa, hevea, many orchids, vines, melon tree, and ceiba grow here. Many animals are adapted to life in trees: prehensile-tailed monkeys, sloths, arboreal porcupines; Tapirs, anteaters, and jaguars also live here;
many species of parrots, hummingbirds; the world of insects is very rich; Snakes, including anacondas, are common. The forests have up to 12 tiers.
2) The zone of variable-humid equatorial forests is located north and south of the jungle, in the west of the Atlantic coast. It is formed within subequatorial climatic zones. Red soils and yellow soils are formed here. Vegetation and fauna are the same as in
3) The savannah zone occupies the Orinoco Lowland and most of the Guiana and Brazilian plateaus. It is located in the subequatorial climate zone. Red ferralitic and red-brown soils are formed here. Savannahs of the northern and southern hemispheres within the Southern
Americas are different. In the northern savannas (llanos), palm trees and acacias, mimosas, milkweeds, and bottle trees grow among the grasses. In the southern savannas (campos) the vegetation is poorer due to less rainfall: there are low-growing woodlands of Quebracho with very hard
wood. Among the animals in the savannas live small deer, wild peccary pigs, armadillos, anteaters, jaguars, pumas, and rhea ostriches.
4) The tropical desert zone occupies a small coastal strip on the west coast. Here, not far from the ocean, lies one of the most waterless deserts in the world - the Atacama. Cacti and thorny cushion-shaped bushes grow here and there on the rocky, infertile soils. On shore
There are bird colonies on the rocks.
5) The steppe zone (pampa) is located south of the savannas. In the hot tropical climate, fertile red ferralite soils were formed here. The main vegetation is grasses, among which feather grass, wild millet and other cereals predominate. In the southwest, where there is less
precipitation, there are thickets of thorny grasses and shrubs. Fast-running animals are typical for the pampas: pampas deer, pampas cat, several types of llamas. Lots of rodents (nutria, viscacha), as well as armadillos and birds.
6) The zone of semi-deserts and temperate deserts was formed in Patagonia in a temperate climate with low rainfall. The soils are poor brown and grey-brown. The vegetation is represented by dry grasses and cushion-shaped shrubs. The fauna is similar to the pampa, with rodents and burrowing animals living there. Among them are nutria and small armadillos.
7) Altitudinal zone.
In the equatorial zone: up to 1000 m - humid equatorial forests.
Up to 3000 m there are mountain and high-mountain forests where bamboo and tree ferns and cinchona are found.
Up to 4000 m - low trees and shrubs and woodlands appear. There are heather and myrtle thickets, and low-growing bamboos.
Above 4000 m there are alpine meadows (paramos). The vegetation consists of rare cereals and cushion-shaped shrubs. Flat areas have moss swamps, while large slopes are characterized by rocky, barren deserts.
Above 4500 m there are bare rocks, a belt of eternal ice.
In the subtropics, at the foot, there are deserts, turning into a belt of hard-leaved forests, extending to an altitude of 2000 m on the western slopes and up to 1800 m on the eastern slopes. Here you can find plane trees, glanders, and in the undergrowth there are thickets of flowering geraniums. Hard-leaved forests give way to deciduous beech forests, and above 2500 m there are mountain meadows.
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Tectonic map
At the base of the continent lies the South American Plate, so most of the terrain is plain. In the west there is an area of new folding, where the relief is mountainous. The central and eastern parts are occupied by plains (lowlands, hills and plateaus), and the Andes mountains in the west.
The Andes are the longest (9000 km) and one of the highest (Mount Aconcagua, 6962 m) mountain systems on Earth, bordering all of South America from the north and west; southern part of the Cordillera. In some places, the Andes reach a width of over 500 km (the greatest width - up to 750 km - in the Central Andes, between 18° and 20° S). The average altitude is about 4000 m.
The relief of the eastern part was formed on the ancient South American platform. The rise of its foundation in relief corresponds to plateaus, and low-lying plains have formed in the troughs. The most powerful tectonic movements occurred on the shields; they are broken by cracks and there are faults. Erosion processes, weathering, and tectonic processes have created a wide variety of landforms on the Guiana and Brazilian plateaus.
The lowland plains (Amazonian, Orinoco, La Plata) have a flat topography and are composed of marine and lacustrine-fluvial deposits.
Features of the relief forms of South America
The relief of the western part of the continent is the result of the interaction of several lithospheric plates, on the border of which mountain-building movements occur. The formation of the Andes began in the Paleozoic and has not ended yet. The Andes continue to rise, volcanoes erupt, and strong earthquakes occur.
Physiographic characteristics of the Interior Plains of South America.
The interior plains are located between the Brazilian Plateau and the Andes in the central part of the continent and are confined to three zones - subequatorial, tropical and subtropical. The Interior Plains includes five natural regions: Mamore, Pantanal, Gran Chaco, the interfluve of Parana and Uruguay, and Pampa.
Mamore Plains— flat alluvial plains . In summer, equatorial air masses bring heavy precipitation here, up to 2000 mm per year. In winter there is less rain, but the dry season is weakly expressed, so the composition of woody vegetation is closer to the hylae of the Amazon.
N variability of the Pantanal , dry in winter and flooded in summer with rainwater. It is composed of a thick layer of sedimentary rocks. The Pantanal plains are dominated by tall grasses and here and there trees and shrubs. Moisture-loving forests grow along the rivers.
Plains of the Gran Chaco. This is the hottest place in South America, the average January temperature is + 28, + 29 ° C, the absolute maximum is + 47 ° C. The alternation of the winter dry and summer rainy seasons is well expressed in the region. Precipitation is predominantly rainfall. In the western, more elevated part of the region, there are forests of prickly acacias, cacti, and agaves; areas of steppes and forests appear to the east. In wetter places the wax palm grows. In the north of the region there are extensive wetlands.
Interfluve of Parana and Uruguay It is a plain up to 100 m high. The climate here is subtropical, humid, with an even distribution of precipitation over the seasons, with over 1000 mm falling during the year. The northern part is swampy; the center and south of the interfluve are a well-drained, slightly hilly plain, composed of sandstones covered with marls. The black-colored soils of subtropical savannas are well developed; forests of mimosa and acacia grow here. There are areas of subtropical steppes.
The southern part of the Interior Plains is occupied by Pampa - grassy plains. The climate of Pampa is subtropical. The average temperature in January is + 22 - + 24° C, in July + 7 - + 9° C; precipitation falls 1000-1200 mm per year, it is distributed evenly across the seasons.
In the flora of Pampa there are up to a thousand species of different cereals. There are areas devoid of grass. On the clayey soils of Pampa, the grass silvery gynerium is present. The fauna of Pampa is not rich and monotonous. Vizcacha, a large rodent, is often found. Rare predators (puma). Typical birds are the ibis, ipikaha, and tinamous, which are similar in size and appearance to a partridge.
44. Precordillera and Pampinsky Sierras (physiographic characteristics).
Precordillera - Characterized by great contrasts in relief, climate, soil and vegetation cover. Against the background of elevated plains, steep mountain ranges with a height of 2500-4000 m often rise here. They are composed of Precambrian and Paleozoic rocks, and were subjected to long-term destruction and leveling. Between the mountain ranges, wide valleys formed - bolsons and depressions (Salinas Grande).
The Precordillera is characterized by a continental arid climate. Precipitation falls unevenly. The amount of precipitation decreases from east to west, with the eastern slopes of the mountain ranges receiving more precipitation than the western ones. The river network is poorly developed. A large area is occupied by salt marshes.
The vegetation has a xerophytic appearance; shrub formations of the Monte type are widespread. At an altitude of 500-1000 m, remnants of subtropical forests with hard-leaved evergreen trees and shrubs have been preserved. Above 2500 m the mountain cereal steppe begins.
To the south the forests become thinner. In the southwest, large areas are occupied by semi-deserts with gray soils and salt marshes.
The southeastern part of the Precordillera is occupied by Patagonia. The surface of this natural area is a stepped plateau composed of Meso-Cenozoic deposits. Lowlands are found only in the northeast and southeast. Patagonia's position in temperate latitudes in the western transport zone, between two oceans, should have led to a mild climate and good development of the hydraulic network. The main reason for the aridity of Patagonia is that the dominant westerly winds in these latitudes carry moist sea air from the Pacific Ocean and encounter the Andes mountain barrier. The annual precipitation in Patagonia is 120 - 200 mm. The vegetation cover is dominated by cushion-shaped and creeping forms of shrubs with pronounced xeromorphism; there are few trees. Among the cereals there are plentiful thorny, inconspicuous bushes of harilla, dense cushions of bolax and azorella; southern species of cacti are found.
Among the endemic representatives of the fauna of Patagonia, we should note the Zorillo skunk, the fox-like Magellan's dog, and the Darwin ostrich (the southern species of rhea). Rodents (mara, tuco-tuco, etc.) are also typical, and the Pampas cat and armadillos are also found.
46. Northern Andes (physiographic characteristics).
The mountain ranges of the Northern Andes, dissected by river valleys, stretch from the shores of the Caribbean Sea to 5° south. w. The Northern Andes include the Caribbean Andes, located along the coast of the Caribbean Sea, the Northwest Andes (the Andes of Colombia and Venezuela) and the Andes of Ecuador.
Caribbean Andes Unlike other parts of the mountain system, they have a latitudinal strike. These are the northernmost and youngest ranges, they are more arid than the nearby plains. The mountains are almost devoid of forest cover. The main folding formations in the Caribbean Andes occurred in the Pliocene, when two main anticlinal folds arose - the Coastal and Inner Cordillera. They are separated by a longitudinal depression, now occupied by lacustrine alluvial deposits. The Caribbean Andes have a distinct winter dry season. The lower belt of the mountains is represented by summer-green open forests or thorny shrubs (chaparro) growing on red-brown soils. Higher up, with decreasing temperatures, precipitation becomes greater, so the forests are denser, and evergreens appear at an altitude of 1500-1600 m.
North of the Caribbean Andes are located Caribbean lowlands composed of alluvium. Lake Maracaibo once occupied the entire lowland; now its area is shrinking due to filling with alluvial sediments. At the same time, coastal areas are experiencing gradual subsidence.
The second tectonic trough is occupied by the lowlands of the Magdalena and Cauca rivers, composed of alluvium and coarse clastic material demolished from the Andean mountain ranges Northwestern Andes- the most branched and complexly constructed part of the Andean mountain system. They are located mainly in Colombia. Three main ridges are well defined here - the Western, Central and Eastern Cordillera with a height of more than 5000 m. Among the mountain peaks there are many extinct and active volcanoes. The Central Cordillera reaches the highest average height (Hila volcano, 5750 m, Ruiz peak, 5400 m). The Western and Eastern Cordillera are lower; the latter is divided in the north into two ranges (Sierra de Mérida and Sierra de Perija), covering the lowland of Maracaibo. Between the Eastern and Central Cordillera there is a valley of the Magdalena River - a graben filled with a thick layer of Cretaceous and Cenozoic sediments. To the north-west along the coast of the Pacific Ocean stretches the low Sierra de Baudo, composed of Cretaceous and Tertiary tuffaceous strata.
The Northwestern Andes are located in a subequatorial and equatorial climate. In the direction from north to south, the duration of the dry period gradually decreases, which is practically absent south of Bogota. Mountain ranges in general are abundantly moistened, and on the Pacific coast, due to local circulation and orographic conditions, the amount of precipitation reaches 8000 m (the highest amount in South America). Inland areas are less moistened, but aridity is not pronounced. Climatic features are also reflected in the zonation of soil and vegetation cover. In the west, on the Pacific coast and the slopes of the Sierra de Baudo ridge, a dense mountain hylea is formed. To the east, the amount of precipitation decreases, so the lower parts of the slopes are covered with summer-green open forests and shrubs, higher up - with mixed, deciduous-evergreen forests, and only at an altitude of 1000 m does wet mountain hylea begin. Here you can find the toquilla palm, balsa wood with very light wood, and a number of wood species typical of the Amazon. The avifauna is richly represented - up to 1500 species. Parrots, hummingbirds, and sunbirds are typical.
Higher up, as the temperature decreases, belts of open forests and crooked forests appear; at an altitude of 2500-3500 m, the mountain meadows of paramos extend.
Geological structure, relief, minerals of South America
Even higher up there are peculiar associations of uplands of herbaceous vegetation with individual shrubs and cacti. The interior slopes of the northwestern Andes are drier. Hard-leaved or summer-green forests grow here.
Andes of Ecuador(from 2° N to 5° S) - the narrowest part of the Andes, high-mountain and tectonically active. Two parallel chains are well defined in them - the Eastern Cordillera and the Western Cordillera, separated by a number of intermountain basins. The total width of the mountain system here is about 90 km. The ridges consist of separate mountain ranges, separated by saddles that are poorly defined in relief. The main peaks are, as a rule, active and extinct volcanoes, including the highest of them, the Chimborazo volcano (6267 m). The known active volcanoes are Cotopaxi, Antisana, and Sangay. Intermountain basins are located at an altitude of 2500-2800 m, they are filled with a layer of volcanic ash, tuff and alluvium. The epicenters of earthquakes are most often located in the area of the intermountain valley separating these Cordillera chains.
To the west of the Andes mountain range lies a strip of the Costa coastal plain, with a hot and humid climate. Here there is a rapid decrease in precipitation from 1200-1500 mm in the northern part (with high relative humidity) to 400 mm in the south. These changes are reflected in the vegetation cover. Savannas with areas of wet equatorial forests, occupying the northern part of the Costa, are gradually replaced to the south by dry steppe vegetation. In the mountainous part, vertical zonality is well defined. Up to 800-1000 m, the change in climate and vegetation cover is still weakly felt, then the amount of precipitation increases noticeably, the amplitude of temperatures decreases, with a general decrease. Cinchona, balsa, and ceiba trees appear in this belt. From an altitude of 1500-1800 m, palm trees disappear, and tree ferns become more numerous. Above 3000 m, vegetation of the paramos type predominates on mountain meadow and mountain steppe soils. Eternal snow begins at an altitude of 4200-4500 m. The mountain climate is more favorable for human life than the climate of Costa and Gil.
Relief. The relief of South America clearly distinguishes the flat-platform platform extra-Andean East and the mountainous Andean West, corresponding to the mobile orogenic belt. The uplifts of the South American platform are represented by the Guiana, Brazilian and Patagonian plateaus, the troughs - by the lowlands and plains of the Llanos-Orinoco, Amazon, Beni-Mamore, Gran Chaco, Mesopotamia (Parana and Uruguay rivers) and Pampa; from the east. The plateaus are framed by narrow intermittent strips of coastal plains.
The Guiana Plateau rises towards the center (Mt. Neblina, 3014 m), the Brazilian - from the north-west. to the south-east (city of Bandeira, 2890 m), Patagonian - from east to west (up to 2200 m). The relief of the Guiana and Brazilian plateaus is dominated by basement gently undulating plains (up to 1500-1700 m high), within which there are remnant cone-shaped peaks and ridges (for example, Serra do Espinhaço) or table, predominantly sandstone, hills - the so-called chapadas (Auyan-Tepui and Roraima, etc.). The eastern edge of the Brazilian Plateau is divided into separate massifs (Serra da Mantiqueira, etc.), which have characteristic “sugar loaf” shapes (for example, Pan de Azucar in Rio de Janeiro). The troughs and depressions of the Brazilian Plateau in the relief are expressed as monoclinal-layered plains with raised edges-cuestas, accumulative plains (the depression of the São Francisco River, etc.) or a lava plateau (in the middle reaches of the Paraná). The relief of Patagonia is dominated by layered, including volcanic, stepped plateaus, covered by ancient moraine and fluvio-glacial deposits; the plateaus are cut by deep canyons of rivers emerging in the Andes; arid forms of denudation are characteristic.
The Andes ridge system extends over 9,000 km to the north and west of the continent. In the north and northeast, in Venezuela, there are two chains of the Caribbean Andes, deeply dissected by faults and river erosion. The main, meridional system of the Andes, or Andean Cordillera (Cordillera de los Andes), reaching 6960 m (Aconcagua), rises in the west of SA. and is divided into Northern, Central and Southern Andes. The northern Andes (up to 5° S) are distinguished by the alternation of high folded-block ridges and deep depressions. In Ecuador, they consist of the Eastern and Western Cordillera, the depression between which is filled with the products of the activity of the volcanoes Chimborazo, Cotopaxi, etc. In Colombia, there are three main Cordilleras (Eastern, Central and Western), separated by depressions of the river. Magdalena and Cauca. Volcanoes (Hila, Ruiz, Purase, etc.) are concentrated mainly in the Central and Southern Western Cordilleras; For the central part of the Eastern Cordillera, ancient lake plateaus are typical, with an altitude of 2-3 thousand m. In the north and west lie the largest lowlands in the Andean west - the Caribbean and Pacific.
The Central Andes (up to 27-28° S) are much wider and more monolithic than the Northern Andes. They are characterized by internal plateaus raised to 3.8-4.8 thousand m, bordered by marginal ridges; the highest mountains bear significant glaciation. The southern part is the Central Andian Highlands - the widest (up to 750 km) section of the Andes; its main element is the Puna plateau with the ancient lake plateau of the Altiplano in the southwest and a number of blocky ridges in the east and south. In the east, Puna is framed by the Cordillera Real, with the volcanic Western Cordillera in the west (the 2nd volcanic region of the Andes with the volcanoes Misti, Llullaillaco, Sajama, and others), a longitudinal tectonic depression (with the Atacama Desert) and the Coastal Cordillera.
In the Southern Andes in the north (up to 41°30" S) the relief is expressed by: the double Main Cordillera (the city of Aconcagua in the eastern, or Front), to which the Precordillera massifs are attached to the east; the Longitudinal Valley of Chile and the Coastal Cordillera. Between 33-52° S there is another volcanic region of the Andes with a large number of active volcanoes to the west of the Main Cordillera and extinct ones to the east of it. In the southernmost section of the Andes - the Patagonian Andes - the Coastal Cordillera turns into an archipelago of islands. The longitudinal valley - into the system of straits, and the flooded troughs of the sharply declining Patagonian Cordillera - into the fjords. Modern glaciation in South Africa occupies an area of 25 thousand km 2, of which over 21 thousand km 2 are in the Southern Andes. There are also glaciers in the Western Cordillera, between 9 and 11° latitude and on the islands of Tierra del Fuego.
Based on the relief features, the territory of South America can be divided into two parts. In the eastern and central parts of the continent there are predominantly flat areas with varying altitudes above sea level. In the north and west along the ocean coast, stretches the world's longest mountain system - the Andes. \
The reasons for such relief features in the geological history of our planet. The eastern and central lowland part of South America is located on an ancient and rigid landmass - the platform. Western and northern - formed and continues to form as a result of the constant interaction of two lithospheric plates. Together, the oceanic plate, unable to withstand the resistance force of the more rigid continental plate, is pushed under it, as if under an ice floe, plunging into the mantle. A deep oceanic trench forms along the western coast of South America. Unable to withstand the enormous pressure, the edge of the continental plate is constantly crushed and continues to fold into folds. This is how the Andes were formed.
Mountain-forming processes are still taking place today. This is evidenced by the constant rise of mountains, as well as frequent earthquakes and volcanic eruptions. Scientists have discovered that the periodicity of crustal movements in this place reaches 10-15 years. Relief of South America. The Andes are young mountains with high peaks and steep slopes. The greatest peak of this mountain system and the entire western hemisphere is Mount Aconcagua (6960 m).
The tops of the mountains are covered with perennial snow and glaciers. There are many extinct and active volcanoes in individual mountain nodes. Among them, the active volcano Cotapahi (5897 m) stands out, which the Indians called “Shining Mountain”.
The movement of glaciers and erosion processes have created many bizarre and amazing relief forms in the Andes. The relief is completely different in the central and eastern parts of South America. Here you rarely see sharp fluctuations in heights, there are rarely earthquakes, and there are no active volcanoes at all. The platform is dominated by slow vertical movements of the earth's crust. At the same time, deep faults were formed, through which magma penetrated into the layers of rocks; sometimes it spilled out to the surface in the form of lava.
Vertical movements caused the formation of the Brazilian and Guinean plateaus. Since they are elevated above the surrounding area, intense erosion processes began here. In the troughs of the platform there are low-lying plains - Amazonian, Orinoco, La Plata. The relief here, unlike the plateaus destroyed by erosion, is very monotonous. They have a flat, often marshy surface. The modern relief of these territories was formed as a result of the removal and deposition of products of destruction of elevated areas of the continent by numerous deep rivers over many millions of years.
