Introduction

The theme of this work - "Complex characteristics of the Amazon", is taken by us, because the Amazon is a very important link geographical envelope. The relevance of this topic lies in the fact that the Amazonian forests are rightly called the "lungs of the globe" and if they are cut down uncontrollably, this would inevitably lead to a global natural disaster.

aim of this work is complex characteristic Amazon. To achieve this goal, the following tasks:

1. Determine geographical position on the world map

2. Characterize the relief in connection with the tectonic structure

3. Determine the type of climate and characterize it

4. Describe inland waters

5. Describe the flora and fauna

6. Describe natural resources

7. Reveal the anthropogenic impact on nature

Source base: various Internet sources, world atlases - GAU and FGAM atlases were used to complete the tasks.

Position on the mainland

Located on the mainland of South America, in its northern part. The boundary is clearly defined: from the north - the Guiana Highlands, from the south - the Brazilian Highlands, from the west - the eastern foot of the Andes, and in the east is the mouth of the Amazon River, which flows into the Atlantic Ocean (Fig. 1).

The physical-geographical boundaries of the region almost everywhere coincide with the boundaries of the Amazonian lowland. Only in the north, the southernmost margin of the Orinoco lowland belongs to the region, and the southwestern part of the Amazonian lowland in the upper part of the river basin. Madeira, according to natural conditions, belongs to a different physical and geographical area.

Amazonia is located within 78? z.d and 50? h.d; from about 2? NL and up to 7? S

The territory of the Amazon covers an area of ​​​​about 5 million square meters. km. In size, it surpasses the physical and geographical regions of not only South America, but also other continents.

Rice. one

Tectonic structure and relief

The Amazonian lowland is an area of ​​prolonged subsidence within the platform, and almost throughout its entire territory has low altitudes and a uniform flat relief. Even at the very foot of the Andes, the height of its surface does not exceed 100 m above sea level.

Only in the southwest, from the side of the Andes, sandstone plateaus rise, dissected by deep river valleys, and in the northwest, the Pardaos massif (900 m) rises, tectonically close to the Guiana Highlands.

In the east, the ancient foundation of the mainland is uplifted and lies relatively close to the surface. This is associated with a general elevation of the terrain up to 200-250 m above sea level and a deeper incision of river valleys, in which crystalline rocks of the Gondwana basement are exposed.

The main part of the territory of the Amazon is occupied by the huge alluvial plain of the Amazon, formed from vast platform syneclises merged with each other, filled with marine and continental sediments.

The surface of the Amazonian lowland is covered with a thick layer of Tertiary and Quaternary deposits, mainly of riverine origin. Thick strata of alluvial accumulations along the rivers are constantly replenished during the annual floods. In the western part of the lowland, approximately to the confluence of the river. Madeira to the Amazon, river valleys are almost not cut into the surface and there are almost no differences in relief between valleys and watersheds. Along the rivers stretch bands of powerful young alluvial deposits, which are constantly replenished.

Modern landscapes of the Amazon are largely dependent on its climate.

big, East End mainland is a platform. In the north and west, it is bordered by a zone of geosynclinal structures.

The foundation of the platform of South America is mostly Precambrian in age, and in the south - Hercynian. On this basis, on the modern tectonic South America, the Guiano-Brazilian (South American) platform is distinguished on the Archean-Proterozoic folded basement and the Patagonian platform on the Hercynian base. The development of platform structures in South America obviously took place in close connection with the platforms of other continents of the southern hemisphere - Africa, Australia, and. The structure of the platform is characterized by the presence of protrusions ancient foundation and depressions, in which the ancient folded base is hidden under layers of younger sedimentary deposits. Ledges usually correspond to the highlands of the eastern part of the mainland, depressions - lowlands. However, there is no complete coincidence of structure and relief.

Precambrian orogenic cycles covered a significant part of South America. It is possible that 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 basin of the Andean geosyncline, which continued in the north with the Cordillera geosyncline of North America.

In the Cambrian, a significant trough occurred at the site of the Amazonian lowland, which then spread into the basin. The sea occupied large areas in the Devonian, and in the Carboniferous period its area again decreased. Obviously, in the southern part of the mainland, approximately south of 37 ° S. sh., from the beginning of the Paleozoic there was a deflection of the geosynclinal type, in which mountain building occurred during the Hercynian cycle, which led to the creation of the Patagonian platform. These folded structures (Gondwanids) joined from the south to the Precambrian platform, forming a single whole with it. The Precambrian base of the platform underwent splits during the Hercynian cycle, which were accompanied by powerful eruptions in the southern part of the Brazilian salient. The manifestation of the Hercynian orogeny was also within the Andean geosyncline, and mountain building captured its eastern margin adjacent to the platform.

In the Triassic, a trough formed at the site of the southern part Atlantic Ocean, and Gondwana began to disintegrate.

On the platform during the Mesozoic, the previously formed mountains were destroyed and large masses of continental sediments accumulated, which gradually filled the areas of troughs, turning them into land.

In the Lower Cretaceous, orogeny began within the Andean geosyncline, which first covered it western areas and accompanied by intense volcanic processes. In the Tertiary period, mountain building spread to the eastern parts of the geosynclinal region, and in the Pliocene the Coastal Cordilleras were formed and the final connection between the two American continents took place. The process of mountain building also captured the margin of the platform, as a result of which strongly modified areas of Precambrian and Upper Paleozoic structures were attached to the Andean system.

At the end of the Tertiary and at the beginning of the Quaternary, the entire system was covered by differentiated vertical movements, faults and.

Subsidence at the end of the Tertiary caused a large part of the western margin of the Andes to subside. The modern Andes represent only the eastern marginal part of the fold zone, while its main part is submerged under water. Vertical movements, expressed in the uplift of the rest of the Andes, led to increased denudation and the formation of a number of leveling surfaces and a system of steps, which are distinctive feature relief of the Andes. Volcanism and seismic, as evidence of unfinished mountain building processes, are characteristic of the Andes at the present time. 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 lava outpourings, uplift and subsidence of individual sections, and the associated revival of processes and denudation.

In the Quaternary period, the Andes underwent mountain glaciation. In some places, glaciers went beyond the mountainous country, as evidenced by the accumulation of loess-like deposits on neighboring plains between 30 and 40 .

The following large structural and morphological regions are distinguished on the territory of South America:

The Brazilian Highlands is the most extensive uplift within the platform. It extends in the eastern part of the mainland from 4 to 30 ° S. sh. Most of the upland 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 lowered and overlain by horizontally occurring, but highly elevated Mesozoic deposits. Thus, the inner part of the highlands is in the folded base of the platform.

The eastern and southeastern margins of the massif, facing directly to, are uplifted by faults and are strongly dissected. They break up into a series of ridges, reaching more than 2000 m in height. These ridges, rising high above the ocean or over a narrow coastal plain, gradually descend towards the center of the highlands, turning into a wavy, peneplainized surface with average height 600-800 m. The southeastern edge of the highlands comes close to the coast in the area where the heavily dissected coast, accompanied by small islands, indicates recent land subsidence. To the north and south of this area, the Brazilian Highlands recedes from the ocean, separated from it by a young sandy plain with a lagoonal coast.

The inner part of the highlands, composed of sedimentary rocks, consists of a series of table plateaus with steep slopes. To the northwest and north, the highlands noticeably decrease towards the adjacent lowland plains.

The edges of the highlands in these places are dissected by valleys, and the presence of crystalline is marked by numerous rapids and waterfalls, which abound in tributaries flowing from the Brazilian Highlands.

In the north of the mainland, the vast ledge of the folded base of the South American Platform corresponds in relief to the Guiana Highlands.

The highest and most dissected is the central part of the highlands, between the valleys of the upper Orinoco and Essequibo. Separate ridges crowned with layers 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 margin.

The western part of the Guiana ledge is not 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 which crystalline rocks are covered with strata of Cretaceous and Tertiary deposits and are opened only in the deepest valleys.

In the extreme southeast of the mainland, 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 little dissected, since due to dryness there are almost no watercourses there. The plateau, reaching 1500 m in height, rises to the very shore of the Atlantic Ocean and breaks off to it with hundred-meter steps.

On either side of 30° S. sh. there is a section of the platform that was subjected to late Tertiary uplifts due to mountain building within the Andean geosyncline. At present, meridional blocky ridges are rising there, composed of crystalline rocks and reaching heights from 2000 to 6000 m. Depressions filled with continental deposits lie between the ridges. The ridges, called the Pampina Sierras and, are partly part of the Andes system.

The most extensive lowland of South America - the Amazon - one of the largest on the globe, was 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 submerged to a depth of many thousands of meters. In the western part, the surface of the lowland is almost perfectly flat. To the east, i.e., downstream of the Amazon, the Guiana and converge and the alluvial lowland is preserved only in the form of a wide strip along the Amazon. To the south and north of the valley, the crystalline basement of the platform lies close to the surface and is exposed by deep valleys of the Amazon tributaries.

In the trough between the Guiana Highlands and the Andes, it is filled with marine tertiary sediments and continental sediments carried from neighboring mountains. Its western part is lower and flatter, the eastern part is uplifted and dissected by deep river valleys on a plateau 200-300 m high. At the confluence of the Orinoco into the Atlantic Ocean, a flat marshy delta plain with traces of recent subsidence was formed.

In the southeast of the mainland near the parallel 40 ° S. sh. the Andes are joined in the form of blocky ridges by the Mesozoic uplifts of the Hercynian structures of the Natagonian platform, the so-called "".

The resources of South America have been explored very unevenly. But even what is already known testifies to the enormous wealth of the mainland in various forms. The deposits of various metal ores are especially large, associated both with the oldest crystalline rocks of the platform basement and with volcanic processes that took place in the Andean geosynclinal region. But on the mainland there are also large reserves of minerals of 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 connection with the processes of volcanism and contact metamorphism. There are deposits of tin, tungsten, antimony, lead, zinc and silver. Polymetallic ores containing lead, zinc and gold are widespread in the territory, reserves of gold and platinum are on the territory. Chile is rich in copper and contains one of the largest copper deposits in the world. the globe, formed in connection with the processes of tertiary volcanism. In addition, on average Chile has large deposits radioactive elements. Sulfur deposits are associated with the processes of volcanism in the Andes.

There are deposits of ores in the Brazilian and Algonquian shales and conglomerates (the largest of them are in the southeast of the Brazilian Highlands and on the northern slope of the Guiana Highlands). Approximately in the same areas, manganese ores occur, formed as a result of ancient crystalline rocks.

Numerous gold deposits are associated with ancient intrusions and metamorphic processes, occurring on the southeastern margin of the Brazilian Highlands and in the northeast of the 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 basement.

The entire territory between the Andes and the Brazilian Highlands, the intermountain basins and the coastal zone of the Andes are rich. Its especially large reserves are concentrated 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 also discovered within the platform - in Patagonia, on the Amazonian lowland and on the Brazilian Highlands.

On the coast Pacific Ocean, Atacama and offshore islands are the only deposits of natural saltpeter in the world. It is a product of the decomposition of organic remains accumulated in dry and hot climates during previous geological periods.

The process of formation of valuable organic substances (guano), used as fertilizer, is taking place on the coastal islands of the Pacific Ocean at the present time. The material for this is organic remains accumulated by birds nesting there.

Remember: 1. In what part of the South American lithospheric plate is the mainland located? What part of South America is located on the edge of the lithospheric plate? 2. How are tectonic structures, landforms and the distribution of mineral deposits related? 3. What landforms prevail in Africa?

Tectonic structure. As a result of the split of Gondwana 180 million years ago, South America separated from Africa and began to move west. This is how the South American lithospheric plate. So, the basis of South America is a fragment of Gondwana - the ancient South American platform, which occupies the entire eastern part of the mainland. Its age is several billion years. In some places, the crystalline foundation of the platform comes to the surface, forming shields. The largest of them is the Brazilian Shield in the east and the Guianan Shield in the northeast. The rest of the platform has a thick sedimentary cover under which the basement is deeply submerged.

The southern part of the mainland is occupied by a young platform, the foundation of which was formed 300 million years ago and is overlain by a very thick sedimentary cover.

Approximately 65 million years ago, the South American lithospheric plate collided with the Pacific oceanic plates, which led to the formation of a young Andean folding region in the west of the mainland. The collision process continues to this day, so the Andes are characterized by frequent volcanic eruptions and destructive earthquakes.

Relief. The tectonic structure of South America determines its relief. The games of its part are distinguished: low-lying - in the center, flat-mountain - in the east and high-mountain - in the west (see flyleaf 1 of the textbook).

In the eastern part of the mainland on the South American platform are large plains. On the shields are the vast Brazilian and Guiana plateaus. There are many faults that have broken the plateaus into separate arrays. The products of the eruption of ancient volcanoes form "giant steps" with numerous waterfalls on the rivers. The highest part of the Brazilian Plateau (2890 m) is located in the southeast near the coast of the ocean. The impregnable sections of the Guiana Plateau, overgrown with dense forest, gave rise to legends about " lost worlds”, where living creatures, extinct millions of years ago, have survived: huge insects and reptiles. In the central part of the plateau rises to a height of 2810 m.

Giant lowlands are located in depressions in the basement of the platforms, overlain by a layer of sedimentary rocks several kilometers thick. One of them - the Amazonian lowland - is the largest plain in the world (5 million km 2). The surface of the La Plata and Orinokskoy lowlands are marine and continental deposits. low relief in some places break wide river valleys.

The extreme south of the mainland within the young platform occupies the Patagonia plateau, which is adjacent to the mountains in the west.

Along the western coast of the mainland, the longest mountain system in the world, the Andes, stretches for 9000 km. The mountains consist of several parallel ridges, between which are plateaus and depressions. Andes - young mountains, one of the highest on Earth. Approaching, the ridges form high mountain "knots", covered with snow. their height is over 6000 m. They say about the Andes that these are mountain giants, whose “legs” are immersed in humid heat, and their “heads” are covered with “caps” of ice and snow. The Andes is the highest point of all Western hemisphere- Mount Aconcagua, the height of which reaches 6959 m (Fig. 39).

Mountain formation continues, as evidenced by frequent powerful earthquakes and many active and extinct volcanoes. The Andes volcanoes are part of the Pacific volcanic ring. Among them stands out the height of the active volcano San Pedro (5974 m). From the crater of the Cotopaxi volcano (5897 m), a column of steam periodically escapes, which sparkles in the sun and has a noticeable smell of sulfur.

By physical map South America, determine the names of the main landforms of the mainland: plains (plateaus, lowlands) and mountains (with the highest point). Explain what tectonic structures they are associated with.

Rice. 39. Mount Aconcagua

Minerals. Due to the tectonic structure, South America is rich in a variety of minerals. Their origin and placement on the mainland is associated with tectonic structures, as well as with the action of internal and external forces Earth.

In the region of the folding of the Andes and in the shields of ancient platforms, mainly ore minerals of igneous origin are located. Thus, as a result of rooting in the faults of magma in the Andes, significant deposits of copper, tin, lead and zinc ores were formed. There is also gold, platinum, silver. It is no coincidence that in the Inca language the word Andes means "copper". Volcanic activity in the Andes also caused the emergence of sulfur deposits, mainly in Chile. Colombia is home to world famous emerald deposits.

Significant saltpeter deposits have formed on the Pacific coast in places of "bird markets", which is a consequence of the decomposition of bird droppings.

Large reserves were found on the Brazilian and Guianan Plateaus iron ores, which is associated with the release of ancient crystalline rocks of the platform. Significant deposits of manganese and nickel ores and bauxite have also been found here.

Oil and natural gas deposits have been found in the depressions and troughs of the platform, covered with a sedimentary rock cover. Their main reserves are located in the north and in the central part of the mainland.

Briefly about the main thing!

Three large tectonic structures form the foundation of South America: the ancient South American platform in the east, the young platform in the south, and the young folding area in the west.

The tectonic structure in the relief of the mainland is due to a clear distinction: the flat east, which includes lowlands and plateaus, and the mountainous west of the Andes.

South America is rich in a variety of minerals, especially in metal ores and oil.

1. What is the difference between the relief of the eastern and western parts of South America? How is this related to the tectonic structure of the mainland?

2. Name and show on the map the largest plains of the mainland and the highest peaks of the Andes.

3. Explain the patterns of distribution of mineral deposits in South America, depending on the tectonic structure.

4. Explain why the Andes, formed in the west of South America, is the longest mountain system on Earth.

5. Think Than Similar tectonic structure and relief of South America and Africa. What is the difference?

6. Find on political map South America such countries: Brazil, Argentina and Chile. Explain possible. strong earthquakes within these countries.

South America.

I. General information
Yu. A. - the southern mainland of the Western Hemisphere between 12 ° 28 "N (Cape Gallinas on the Guajira Peninsula) and 53 ° 54" S. sh. (Cape Froward on the Brunswick Peninsula), 34°47"W (Cabo Branco Point) and 81°20"W. (Cape Parinas). In the north, the mainland is washed by the waters of the Caribbean Sea, in the east by the Atlantic Ocean, in the south by the Strait of Magellan, and in the west by the Pacific Ocean. The narrow Isthmus of Panama connects South America with Central and North America. The area of ​​the mainland is 17.65 million km2, with islands 18.28 million km2. South A. includes the islands of Leeward and Trinidad, the Falkland Islands, and the Tierra del Fuego archipelago (to the south of which Cape Horn is located on the island, the southern tip of all of South A. is 55 ° 59 "S), the islands of southern Chile, Galapagos and others

The coasts of Yu. A. are very weakly dissected, only in the south-west. they are heavily indented by fjords. Separate large bays protrude deeply into the land: in the west, the Gulf of Guayaquil; in the north, the Gulf of Venezuela and the lake-lagoon of Maracaibo; and in the southeast. - Bay of La Plata. On the Pacific coast (except for the southwest), rectilinear leveled abrasion bay and accumulative coasts predominate, while in Peru they are predominantly rocky. On the Atlantic coast, the coasts are also leveled, but already low-lying. South of Guanabara Bay to 30°S sh. the coasts are finely dissected and have convenient ingressive bays; open crescent-shaped bays are typical of the coasts of Patagonia.

II. Nature
In the relief of South Asia, a plain-flat platform extra-Andean East and a mountainous Andean West, corresponding to a mobile orogenic belt, are clearly distinguished. The uplifts of the South American platform are represented by the Guiana, Brazilian and Patagonian plateaus, the troughs are represented by the lowlands and plains of the Llanos-Orinoco, Amazonian, 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 (the city of Neblina, 3014 m), the Brazilian - from the northwest. to the south-east (Bandeira, 2890 m), Patagonian - from east to west (up to 2200 m). The relief of the Guiana and Brazilian plateaus is dominated by socle gently undulating plains (up to 1500-1700 m high), within which remnant cone-shaped peaks and ridges (for example, Serra do Espinhaso) or table, mostly sandstone, uplands - 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.), having characteristic forms"sugar loaves" (for example, Pan di Asucar in Rio de Janeiro). The troughs and troughs of the Brazilian Plateau are expressed in relief as monocline-stratal plains with raised cuesta edges, accumulative plains (the depression of the San Francisco River, etc.), or a lava plateau (in the middle reaches of the Parana). The relief of Patagonia is dominated by layered, including volcanic, stepped plateaus, covered by ancient moraine and water-glacial deposits; the plateaus are cut by deep canyons of rivers originating in the Andes; arid forms of denudation are characteristic.

The Andean ridge system extends for 9,000 km to the north and west of the mainland. 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 South Africa and is subdivided into the Northern, Central, and Southern Andes. The northern Andes (up to 5° S) are distinguished by the alternation of high fold-block ridges and deep depressions. In Ecuador, they consist of the Eastern and Western Cordilleras, the depression between which is filled with the products of the activity of the volcanoes Chimborazo, Cotopaxi, and others. Magdalena and Kauka. Volcanoes (Huila, Ruiz, Puras, and others) are concentrated mainly in the Central and South Western Cordilleras; The central part of the Eastern Cordillera is characterized by ancient lacustrine plateaus, 2,000 to 3,000 m high. In the north and west lie the Caribbean and Pacific lowlands, the largest in the Andean west.

The Central Andes (up to 27-28 ° S. latitude) are much wider and more monolithic than the Northern ones. They are characterized by internal plateaus raised up to 3.8-4.8 thousand m, bordered by marginal ridges; most high mountains carry significant glaciation. The southern part - the Central Andean Highlands - the widest (up to 750 km) segment of the Andes; its main element is the Puna plateau with the ancient lake Altiplano plateau 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 western volcanic Cordillera Western (the second volcanic region of the Andes with Atacama Desert) and the Coastal Cordillera.

In the southern Andes, in the north (up to 41°30" S), the relief shows the double Main Cordillera (the city of Aconcagua in the east, or Peredovaya), 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 large quantity active volcanoes to the west of the Main Cordillera and the extinct ones - to the east of it. In the southernmost segment of the Andes - the Patagonian Andes - the Coastal Cordillera turns into an archipelago of islands, the Longitudinal Valley - into a system of straits, and the flooded troughs of the sharply declining Patagonian Cordillera - into fjords. Glacial forms dominate. Modern glaciation in South Africa covers an area of ​​25,000 km2, of which more than 21,000 km2 is in the Southern Andes. There are also glaciers in the Western Cordillera, between 9 and 11 ° S. sh. and on the islands of Tierra del Fuego.

Geological structure and minerals
The Yu.A. continent consists of two main structural elements- the South American platform in the center and east and the folded mountain belt of the Andes, framing the continent from the north, 3. and south.

The basement of the South American Platform consists of blocks of different ages, consolidated from the Archean to the Early Paleozoic. The largest basement projections are the Guianan, West Brazilian and East Brazilian shields; the first two shields almost entirely consist of deeply metamorphosed and intensely deformed Archean and Lower Proterozoic rocks (gneisses, crystalline schists, and granites), as well as Middle or Upper Proterozoic rapakivi-type granites. The East Brazilian Shield includes individual blocks of the Early Precambrian (the San Francisco massif and others), separated and bordered by late Proterozoic geosynclinal folded systems. In the Cambrian-Ordovician, their ancient basement was intruded by numerous intrusions of granitoids and accompanying pegmatites. On the Guiana and West Brazilian shields, remnants of an ancient, protoplatform cover composed of red-colored detrital sequences and covers of basalts with dikes and sills of gabbrodiabases have been preserved that make up the watershed areas; a younger cover (middle - Upper Paleozoic and Mesozoic) fills the depressions of the platform. At the end of the Carboniferous and the beginning of the Permian, the territory south of the Amazon was covered by a sheet of glaciation. Climate warming led to the replacement of glacial deposits (tillites) with coal-bearing ones (Lower Permian), and then arid ones - mainly sandstones (Upper Permian - Cretaceous).

The latitudinal Amazon basin was founded at the end of the Precambrian - the beginning of the Paleozoic along major zone faults that separated the Guiana and West Brazilian shields. An ancient strip of depressions of meridional strike separates the East Brazilian Shield from the West Brazilian Shield; its middle link - the San Francisco depression - is superimposed on the ancient massif of the same name and developed mainly at the end of the Precambrian. The northern and southern basins - the Maranhao (Paranaiba) and Parana syneclises - are composed of the Middle and Upper Paleozoic and Mesozoic, and in the Parana syneclise, basalt covers, sills and dikes of basic rocks (traps) of mainly Early Cretaceous are widely developed. In the Late Cretaceous - Early Paleogene, numerous intrusions of ultrabasic-alkaline rocks, including alkaline granitoids, arose within the East Brazilian Shield.

The southern part of the South American Platform - the Patagonian Plate - is distinguished by the youngest basement, including the lower Paleozoic; usually regarded as a stand-alone structural unit, consisting of two uplifts - North Patagonian and South Patagonian (Deseado and Santa Cruz) and two troughs: Neuquen - San Matias and Chubut - San Jorge. The southernmost part of the plate passes into the Magellanic Foredeep of the Andes. A system of perioceanic subsidences associated with the formation (beginning from the Cretaceous) of the oceanic basin of the South Atlantic has developed along the Atlantic coast of South America. Cretaceous deposits (continental, salt-bearing and marine) are filled with grabens and semi-grabens. Cenozoic composes coastal plain and the shelf, lying with a very gentle slope towards the ocean.

The folded mountain belt of the Andes consists of several segments that differ markedly in their geological history and building. The latitudinal-trending coastal ranges of Venezuela, located in the north, form the southern flank of the Antilles arc; composed mainly of the Mesozoic, starting from the Jurassic, and the Cenozoic. The northern Andes proper (the west of Venezuela, Colombia, and Ecuador) are represented by a bunch of ridges radiating northward; they correspond to large young anticlinoria. The Eastern Cordillera of Colombia, the Sierra Merida, the Sierra de Perija, and the Sierra Nevada de Santa Marta arose on a Precambrian granite-metamorphic basement overlain by Paleozoic and Mesozoic epicontinental strata. The Central Cordillera of Colombia and the Eastern Cordillera of Ecuador are composed mainly of metamorphosed Paleozoic rocks that have experienced folding, with the intrusion of granites at the end of the Paleozoic. The uplifts are separated by intermountain troughs (Maracaibo, Magdalena, Cauca-Pathia), made by Cenozoic molasses. The Central Andes are distinguished by a northwestern strike, which at the latitude of the cities of Arica (Chile) and Santa Cruz (Bolivia) is replaced by a meridional one. At this bend, the Andes reach their greatest width. Their eastern part is predominantly composed of intensely folded Cambrian-Devonian rocks unconformably overlain by the Upper Paleozoic volcanic molasse. In the middle part of the Central Andes, the Altiplano graben is located, made predominantly by a thick, mostly Cretaceous continental sequence. To the west stretches a band of Jurassic and Cretaceous sediments with strata of andesites (porphyrites) and large batholiths of Cretaceous-Paleogene granitoids (Western Cordillera of Peru, Main Cordillera of Chile and Argentina). Along the coast of Peru and Chile, the Coastal Cordillera is intermittently traced, composed of a metamorphic stratum of the Late Precambrian - Early-Middle Paleozoic. In the extreme south, the Andes turn to the southeast, passing further into an island arc that borders the Scotia Sea; ophiolites appear in their composition, overlain by the porphyritic series of the Jurassic - lower Cretaceous and Upper Cretaceous - Lower Paleogene flysch; this entire complex of rocks is thrust over the molasses of the Magellanic Trough. In the Cenozoic, the Andes became the scene of intense volcanic activity that continued into modern era in three areas - in Ecuador, in the border region of Peru, Chile and Bolivia and in the central part of Chile; earthquakes are also frequent, including destructive ones (Peru, Chile). From the East, the Andes are accompanied by a discontinuous strip of advanced, so-called. subandian troughs filled mainly by thick Cenozoic molasse.

The bowels of Yu. A. contain a very diverse complex of minerals. The largest deposits of iron ores are confined to the ancient Precambrian of Venezuela (the Orinoco river basin) and Brazil (the state of Minas Gerais), the richest deposits of porphyry copper ores - to the granitoid batholiths of the Central Andes. Deposits of ores of rare elements are associated with ultramafic alkaline intrusions of Eastern Brazil. Deposits of ores of tin, antimony, silver, etc. are confined to young volcanic and subvolcanic bodies in the territory of Bolivia.

The forward and intermountain troughs of the Andes contain deposits of oil and gas along their entire length, which are especially rich within Venezuela. There are coal deposits; deposits of coal are known in the Upper Paleozoic, brown - in the Cenozoic. Bauxite deposits are confined to the young weathering crust (especially in Guyana and Suriname).

67, Relief of South America

Relief and geographical structure. Minerals

The relief of South America is varied and contrasting. According to the nature of the structure of the surface, the mainland is divided into two parts. In the greater eastern territory, formed on an ancient platform, plains and highlands dominate, in the west - the Andes mountains, which arose in a mobile folded region of the earth's crust.

The largest low-lying plains - Amazonian, Orinokskaya, La Platskaya. They correspond to platform deflections. Their relief is rather uniform: flat marshy spaces composed of sedimentary rocks of continental and marine origin.

Raised sections of the platform - shields correspond brazilianandGuiana highlands.

FormationAndes began in the Hercynian folding. The main mountain building is associated with alpine folding, which was accompanied by intense volcanism. During this orogeny, the ancient Hercynian structures were broken into separate blocks and some of them were uplifted to a great height. (Central Andean highlands). And now the Andes continue to form. This is one of the most active tectonic zones of the Earth. Strong earthquakes occur here, volcanoes erupt. The most significant of the volcanoes - Chimborazo, Cotopaxi and etc.

Andes (South American Cordillera)- the longest mountain range on land - 9000. km. Their peaks rise to 6000-6500 m. The highest of them is Mount Aconcagua (6960 m). The ridges of the Andes stretch along the coast, then diverge, then converge and form mountain nodes. Between the ridges in the Central Andes lie a plateau.

The bowels of South America are rich minerals.Huge reserves of ore minerals of igneous and metamorphic origin in the Andes: copper, tin, tungsten, molybdenum, silver, antimony, lead, zinc, platinum, gold, silver, precious stones.

In external features, as well as the internal structure of South America, there is a similarity with North America.

East End, which is part of Gondwana, is characterized by relative stability and the predominance of plains and plateaus in the relief. On the west and northwest mainland, repeating the outlines of its coasts, stretches for 9 thousand km, the longest system of the Andes on Earth, or the South American Cordillera.

The relief of the eastern part is determined by the alternation of protrusions of the ancient Gondwanan foundation and separating them syneclise. The Guiana, East and West Brazilian ledges previously formed a single Guiana-Brazilian megashield. They are separated from each other by syneclises: the Orinoco, elongated along the equator, and the Amazon syneclise, which has merged from three syneclises, to the south - Paraguay-Paranskaya (La Platskaya). Between the West and East Brazilian ledges (shields), in addition to the syneclise of the upper Parana, there are also the depressions of San Francisco and Maranhato (Paranaiba). In the west, at the foot of the Andes, the syneclises join with the Pre-Andean trough.

South of La Plata, the extreme southeast of the mainland occupies Patagonian plate. Within its limits, the Chaco-Austral syneclise, merging with La Plata, and two massifs overlapped from the surface by sedimentary and volcanic strata stand out.

The diversity of the geological structure of the eastern part of the mainland corresponds to the diversity mineral resources.

Large deposits of ore minerals are associated with the rocks of the Archean-Proterozoic basement. The Proterozoic metamorphic rocks of the Guiana and especially the Brazilian ledges (itabirites) contain rich reserves of iron ores - magnetites and hematites. In places where intrusions were introduced, gold deposits were formed. In the products of ancient weathering and decomposition of granite gneisses, large reserves of manganese ores with a metal content of more than 50% were formed. Large deposits of bauxite of world importance are also associated with ancient weathering crusts of crystalline rocks, especially on the Guiana Shield. Deposits of ores of rare earth and radioactive metals were formed in pegmatite veins of various ages. There are large oil fields in the troughs of the Orinoco basin, the Amazon, in the Gran Chaco and on the Patagonian Plate.

Almost all geological structures of the East are directly reflected in the relief in the form of types of morphostructures characteristic of the Gondwanan platforms.

The slopes of the shields (Guiana, East and especially West Brazilian) correspond to basement plains and plateaus. The areas of activation of the East Brazilian and Guiana shields turned into systems of blocky basement ridges (sierras) and massifs.

Along the border of the West Brazilian Shield and the Parana syneclise, as a result of active trap volcanism, which manifested itself during the Mesozoic, the world's greatest basalt step plateaus.

The central parts of almost all syneclises and the zone of the Pre-Andean trough occupy accumulative plains. The marginal parts of the syneclises adjacent to the shields, as well as the region of the Patagonian plate, form high stratified plains and plateaus.

The Maranhato and San Francisco depressions, whose sedimentary complex was uplifted together with neighboring shields, are characterized by the occurrence of high monoclinal and stepped plateaus with steep steep slopes (chapadas).

The folded belt of the Andes almost along its entire length consists of parallel ridges corresponding to anticlinoria, and intermountain valleys corresponding to synclinoria and grabens.

The contemporary folded structure of the Andes includes Paleozoic folded structures reworked by later orogenic processes, to which the central and eastern parts of the mountain system belong. In the west, there is a zone that sank during the entire Paleozoic and Mesozoic and experienced folding and uplift into Cenozoic era. All Andes are characterized volcanogenic landforms.

In the north, the belt of the Andes proper connects with the Antilles-Caribbean region, the main part of which is part of North America. On the southern mainland only the latitudinal system of the Caribbean Andes belongs to this region.

In accordance with the differences in development and structure in the Andes, the following longitudinal structural-geomorphological zones can be distinguished.

Western Cordillera- high and medium height fold-block ridges that arose in the middle or end of the Alpine cycle. From the west, this zone is accompanied by a strip of longitudinal valleys and depressions, separated, in turn, from the Pacific Ocean by a discontinuous zone of the Coastal Cordillera, composed almost everywhere of Cenozoic folded deposits.

Eastern Cordillera formed on Paleozoic folded structures by blocky movements of the end of the Cenozoic. In the central part of the Andes, between the Western and Eastern Cordillera, there are the Punas of the Bolivian Highlands, which are a Paleozoic block that has not experienced significant changes during the Alpine orogeny. Between 26 and 37°S the system of medium-altitude and high blocky massifs and ridges of the Precordillera and Pampina Sierras rises. These mountain structures are the marginal part of the platform involved in the Paleozoic, then in the Cenozoic orogeny. They are separated from the Andes proper and from each other by tectonic depressions and can be considered as a transitional area between the platform and the Andes.

SOUTH AMERICAN EAST

The eastern part of South America, which has a predominantly flat relief, is located between the northern subequatorial and southern temperate climatic zones.

The main factors of spatial differentiation within it are differences in structure and relief(alternating vast shields and syneclise), on the one hand, and zonal structure- with another. Besides, great importance have the contours of the mainland - the greatest expansion of its equatorial part and narrowing in the south; the existence of a mountain barrier from the Pacific Ocean, much greater accessibility from the Atlantic.

For the differentiation of the relief (and, consequently, for the isolation of natural-territorial complexes), the orogenic activation of the near-oceanic and near-Andean margins, the formation of mountains on the Brazilian Shield and the Precordillera were of great importance.

All these features of the South American East create a complex picture of the spatial differentiation of nature within its boundaries and make it possible to distinguish clearly distinct natural regions: the Amazonia, the Guiana Highlands and the Guiana Lowlands, the Orinoco Plain, the Brazilian Highlands, the inland tropical plains, the La Plata region (Pampa) and the Precordillera and Pampina sierras.

Amazonia

Geographical position. The main features of the nature of the Amazon are determined by its flat relief, long-term continental development and equatorial position. This planet's greatest region of equatorial climate and tropical rainforest accounts for most of the basin of Earth's deepest river system.

The boundaries of the Amazon are clearly defined by the slopes of the Brazilian and Guiana highlands and the eastern foot of the Andes.

The main part of its territory is occupied by the huge alluvial plain of the Amazon, formed from vast platform syneclises merged with each other, filled with marine and continental sediments. The axis of the region is the Amazon, which carries its waters from the foot of the Andes to the Atlantic Ocean somewhat south of the equator and collects its tributaries from both hemispheres.

In the western part of the lowland, approximately until its largest tributary, the Madeira, flows into the Amazon, river valleys are almost not cut into the surface and the watersheds between them are poorly expressed in relief. Thick strata of alluvial accumulations along the rivers are constantly replenished during the annual floods. The width of the flooded lanes reaches hundreds of kilometers in some places. Within their limits, the rivers meander, forming many meanders and oxbow lakes. During periods of flooding, numerous and intricate watercourses are interconnected, forming huge water surfaces.

In the east, the ancient foundation of the mainland is uplifted and lies relatively close to the surface. Associated with this is a general elevation of the terrain up to 200-250 m above sea level and a deeper incision of river valleys, in which crystalline rocks of the Gondwana basement are exposed. During floods, only relatively narrow floodplains are flooded, which are limited by distinct ledges of terraces and bedrock banks.

At the mouth of the Amazon, the valley expands again, turning into a vast delta, partly flooded. Within the delta, the river branches strongly and forms a real labyrinth of branches, channels and lakes. Between the main channel of the Amazon and its ancient branch Para is the largest island on Earth, which is washed by fresh waters - Marajo.

Guiana Highlands and Guiana Lowlands

Geographical position. From the coast of the Atlantic Ocean and the Orinoc Lowland towards the Guiana Highlands, the surface rises gradually, in wide steps. The swampy lowland adjacent to the ocean turns into a flat, gently rising plateau, composed of crystalline rocks and forming the basis of the northeastern Guiana ledge of the ancient shield of South America.

Relief. In the central part of the Guiana Highlands reaches greatest height and dismemberment. Separate massifs covered from the surface by layers of multi-colored sandstones and quartzites of the Proterozoic cover, which lie on crystalline rocks, exceed 2000 m, and the highest massifs of the highlands (Roraima and Auyan-Tepui) reach 2772 and 2950 m. heights up to 2000 m or more (Pakaraima mountains, etc.).

The table peaks (tepui) of the highest massifs are devoid of forests; the rocks that make up them, painted in gray, white, red colors, stand out among the greenery that covers the slopes. The red massif of Roraima has long been considered sacred by local Indian tribes, and various legends are associated with it. Rivers flowing from the steep stepped slopes of the highlands cross high ledges and form a large number of waterfalls. There are especially many grandiose waterfalls on the river that crosses the central part of the highlands - Caroni and its right tributaries, flowing down from the highest massifs of the highlands and breaking through the sheer walls of sandstones and quartzites. Hydroelectric power plants have been built on the waterfalls of the Caroni River. In the upper reaches of the Churun ​​River, from the table-like massif of Auyan-Tepui, the highest waterfall in the world, Angel falls down. Its total height is 1054 m, and the height of the free fall of water is 979 m. There are also many waterfalls on the rivers flowing from the highlands to the Guiana lowland. Kaieteur Falls (225 m) on the Potaro River are significantly inferior in height to Angel, but several times higher than the height of Niagara Falls and is one of the largest in the world.

Orinoco plain

Geographical position. The plain forms a wide strip stretching from the shores of the Atlantic Ocean to the Northern Andes, and merges with the Amazon in the southwest. From the south and north it is limited by the Guiana Highlands and the Caribbean Andes.

Relief. Several erosion steps are distinctly expressed in the relief. The lowest step - the lowlands along the Orinoco River and its tributaries - almost nowhere exceeds 100 m above sea level. In areas adjacent to the Atlantic Ocean, the blown sands form dunes. In the north and south, higher isolated flat-topped hills 200-300 m high rise above the lowland, the so-called "mesy".

Piedmont shield-like uplands, even higher than the mesa, are called "piedmonts". In some places they are crossed by crystalline ridges - sierras. The surface of the Mes and Piedmonts is cut by the deep valleys of the largest tributaries of the Orinoco - Meta, Apure and Guaviare. The valley of the latter can be considered the southern border of the entire region. In relation to the entire Orinoco plain, the name "Llanos" is often used (in translation from Spanish "llano" - plain). Since the plains of the Orinoco in their natural state are savannah, the name "Llanos", especially when translated into other languages, is often identified with the concept of "savannah".

brazilian highlands

Geographical position. Between the flat low plains of the Amazon and Parana basins in the north and west and the Atlantic Ocean in the east, a territory with an elevated and dissected relief extends for about 5 million km 2.

relief. The long-term impact of erosion processes, changes in the structure of the earth's crust under the influence of recent tectonic movements have created a wide variety of relief within the highlands, where areas of crystalline plateaus are combined with insular highlands composed of sedimentary rocks, volcanic plateaus and blocky ridges formed as a result of Cenozoic faults and uplifts.

The highest parts of the highlands are located near the Atlantic Ocean and are separated from it only by a narrow strip of coast. Almost everywhere the coastline bears traces of recent subsidence. In some places, small lobed bays cut into the coast, which are convenient harbors. On the shore of one of these bays is one of the largest cities in Brazil - Rio de Janeiro. To the north and south of it, the edge of the highlands recedes somewhat, and wide strips of sandy beaches stretch along the coast of the Atlantic Ocean, partially flooded during high tides.

From the Atlantic Ocean, the eastern and southeastern margins of the Brazilian Highlands look like high and heavily dissected mountains. As a result of the fragmentation and uplift of the East Brazilian Shield in the Neogene, ridges, or "sierras", were formed, which reach a height of more than 2000 m. It is most clearly expressed in the relief of the Serra do Mar in the southeast and the Serra do Espinhasu north of the Southern Tropic. The highest point of the highlands - Mount Bandeira (2890 m) - is located within national park"Caparao".

The subsequent subsidence of the coast separated from the mountainous margin of the mainland the islands with sugar-loaf peaks that surround the bay of Guanabara, on the coast of which Rio de Janeiro stands. In the bowels of this part of the highlands there are rich deposits of iron and manganese ores, radioactive elements, diamonds and gold.

In the northwest and north, socle plateaus are common, into which deep rapids river valleys cut. In the northern spurs of the plateaus in the Serra dos Carajas region, one of the greatest iron ore basins on the planet was discovered, where, in addition to high-quality iron ore, there are deposits of manganese, copper, chromium, nickel ores, bauxite and other valuable minerals. It was there, in the area of ​​mining and to the plants under construction, that the railway line was laid from the Atlantic Ocean, crossing the Eastern Amazon.

In the west and in the central part of the highlands, crystalline rocks are overlain by a layer of limestones and sandstones of Paleozoic and Mesozoic age. Rivers divide them into table heights with steep high slopes (chapads). In the basin of the upper Parana, thick strata of basaltic lavas form stepped plateaus.

From the steps of these plateaus the Parana and its many tributaries rush down, forming rapids and waterfalls, the energy of which is now being intensively used. The most famous is the grandiose Iguazu Falls on the tributary of the Parana of the same name. Throwing 275 jets from the steps of the basalt plateau on the border of Brazil and Argentina, Iguazu has a total width of up to 4 km, and a total height of more than 70 m. Surrounded by lush vegetation, the waterfall is exceptionally picturesque. In both states, national parks have been created around it.

Inland tropical plains

Geographical position. A strip of plains stretched submeridionally inside the mainland (Gran Chaco, Pantanal and Mamore) merges with Amazonia in the north, is bounded by the Brazilian Highlands in the east, the Andes in the west, and Patagonia in the south.

Relief. It is included in Argentina, Bolivia, Paraguay and Brazil. The main features of its nature are flat relief, tropical continental climate, widespread savannas and tropical woodlands. Heights range from 300 to 700 m, in the basin of the upper reaches of Paraguay they do not exceed 200 m. The surface is composed of strata of loose sedimentary rocks.

On the watershed of the river systems of the Amazon and Paraguay, there is an anteclise of the ancient basement, forming a gentle elevation of the Serra dos Paresis with a maximum height of 1425 m. The rivers flowing from this elevation and from the Andes wander along the plain, bringing it with sandy and silty material. The channels of many of them dry up during the dry season. Viscous and swampy muddy strips stretch along these rivers, which are dangerous for people during the rainy season. In the dry season, the silt dries up, forming stable high banks of rivers.

La Plata region (Pampas)

Geographical position. The southern part of the meridional trough between the Andes and the Brazilian Highlands is occupied by the Pampas. It surrounds the La Plata estuary on three sides, and in the east and southeast it goes to the shores of the Atlantic Ocean. From the west, for a considerable distance, its border runs along the uplifts of the Precordillera.

Geological structure and relief. Is it flat or rolling plain, occupying the northeast of Argentina and the whole of Uruguay.

In the northeastern part of the region, within Southern Brazil and Uruguay, the rocks of the Brazilian Shield lie close to the surface and protrude among later deposits, forming uplands and ridges, in places having sharply defined slopes and a height of several hundred meters. These hills, called "cuchilas" by the local population, are often crowned with large blocks of weathered granite. The rivers cutting through the slopes of the hills form deep valleys with rapids and waterfalls.

Towards the ocean and towards the lower reaches of the Parana and Uruguay rivers, crystalline rocks submerge under the sedimentary cover, and the surface gradually levels off. In the interfluve of the Parana and Uruguay and south of La Plata, in the area that is actually called Pampa, the relief is flat, and crystalline rocks are hidden under thick strata of Cenozoic continental deposits. In the area adjacent to La Plata and the Atlantic Ocean, in the so-called Humid, or eastern, Pampas, vast areas of the surface are covered with loess-like rocks, sands and silts; them absolute heights do not exceed 200 m, and near the coast they are less than 100 m.

The low-lying coast with rows of dunes and shallow lakes is cut through by the huge La Plata estuary.

To the south of La Plata, among the flat surface of the Pampas, insular mountain uplifts with a height of more than 1000 m, composed of crystalline rocks, stand out. These are the Sierra de la Ventana and the Sierra del Tandil, collectively known as the Sierra Pampa, or Sierra Buenos Aires. Their steep slopes and jagged ridges stand out sharply from the surrounding terrain.

Precordillera and Pampina Sierras

Geographical position. The natural features of these mountain systems, located entirely within Argentina, are determined by their geographical position within the mainland, between the Tropic of the South and 38 ° S, far from the Atlantic Ocean, near the Andes, which separate them from the Pacific Ocean.

The relief is characterized by the alternation of meridional blocky ridges that arose in the Neogene-Quaternary as a result of orogenic activation of the edge of the platform, with deep basins and flat plains separating them. This region is dominated by semi-desert landscapes with great contrasts in natural conditions.

Geological structure and relief. The eastern ranges of the Pampina Sierras - Sierras de Córdoba and Sierra de San Luis - reach a height of 2790 and 2150 m respectively. To the north, on the western border of the Gran Chaco, rises the over 5,000 m Sierra del Aconquija. In the west, the Sierra de Famatina reaches a height of 6250 m.

The upper parts of the ridges are sections of ancient leveling surfaces, and the slopes are formed by faults from the end of the Neogene and the beginning of the Quaternary. The ridges are separated from each other by grabens filled with clastic masses. The bottoms of the grabens are located at an altitude of 1000-2000 m and are partially or completely occupied by solonchaks, saline marshes and lakes. To the west, a large longitudinal tectonic depression separates the Precordillera from the eastern ranges of the Andes. This depression, formed as a result of recent faults, is subject to earthquakes, sometimes reaching crushing force.

Patagonian plateau

Geographical position. The Patagonian Plateau is the southeastern part of South America within Argentina, the only area that is dry south of 40°S.

A dull, monotonous plateau stretches for many kilometers, covered with tough grasses and thorny bushes, almost devoid of water and relatively sparsely populated.

Geological structure and relief. The Patagonian plateau from the surface is composed of young horizontal sedimentary deposits and covers of dark-colored basaltic lavas. Hidden under these rocks is an ancient foundation close to the surface. In the north, it protrudes onto the day surface, forming a hill, which is cut by deep canyons. The southern part is dominated by volcanic or stratified stepped plateaus, dissected by wide trough-shaped hollows, sometimes dry, sometimes with insignificant streams.

The coast of Patagonia is extremely inconvenient for navigation, as it breaks off to the ocean with steep ledges reaching a height of 100 m or more. From the ocean, the terrain gradually rises, and some massifs of Patagonia reach a height of 1500 m.

The Patagonian plateau breaks off not only to the east, but also to the west, to the Pre-Andean depression located at the foot of the Andes. Within this depression there are many glacial lakes, its surface is cluttered with moraine material. The spurs of the Andes divide the depression into isolated basins.

MOUNTAIN WEST (ANDES)

Mountain system of great extent, with complex orography and diverse geological structure differs sharply from eastern South America.

It is characterized by completely different regularities in the formation of relief, climate, and a special originality of the organic world.

The exclusivity of the nature of the Andes is primarily due to their great length from North to South. The northern, central and southern regions of the Andes differ from each other no less than, for example, the Amazon from the Pampas or the Patagonian plateau.

Depending on the position in a particular climatic zone and on differences in orography and structure, the Andes are divided into regions, each of which is distinguished by its own features of relief, climate and altitudinal zonality.

Allocate the Caribbean Andes, the Northern Andes, located in the equatorial and subequatorial zones, the Central Andytropical belt, the subtropical Chilean-Argentine Andes and the Southern (Patagonian) Andes within the temperate zone. The island region - Tierra del Fuego is especially considered.

Caribbean Andes

Geographical position. The northern latitudinal segment of the Andes from the island of Trinidad to the Maracaibo lowland in terms of orographic features and structure, as well as in character climatic conditions and vegetation forms a special physiographic region.

Geological structure. The Caribbean Andes belong to the Antilles-Caribbean folded region, which in structure and development differs both from the Cordillera of North America and from the Andes proper.

There is a point of view according to which the Antilles-Caribbean region is the western sector of the Tethys, separated as a result of the opening of the Atlantic Ocean.

On the mainland, the Caribbean Andes (Coast Sierra) consist of two anticlines, which correspond to the Cordillera Coast (Cordillera da Costa) and Sierra del Interior (Inner Sierra) ranges, separated by a wide valley of a vast synclinal zone. At the Bay of Barcelona, ​​the mountains are interrupted, breaking up into two links - the western (Andes of Caracas) and the eastern (Sierra de Ocumare). From the side of the platform, the Sierra del Interior is separated by a deep fault from the oil-bearing Subandian trough, which merges in relief with the Orinoco lowland. A deep fault also separates the Caribbean Andes from the Cordillera de Mérida. In the north, a syncline trough, flooded by the sea, separates the anticlinorium of the Margarita-Tobago Islands from the mainland. The continuation of these structures can be traced to the Paraguana and Guajira peninsulas.

The mountain structures of the Caribbean Andes are composed of Paleozoic and Mesozoic rocks crumpled into folds and penetrated by intrusions of various ages.

Relief. Their modern relief was formed under the influence of repeated uplifts, the last of which, accompanied by the subsidence of synclinal zones and faults, occurred in the Neogene. The entire Caribbean Andean system is seismic, but has no active volcanoes. These are the lowest and youngest mountains in the Andes. The highest peaks exceed 2500 m, mountain ranges are separated from each other by through erosional and tectonic depressions.

Northern Andes

Geographical position. Under this name is known the northern segment of the Andes proper from the Caribbean coast to the border between Ecuador and Peru in the south.