Physical geography of South America
South America is the fourth largest of the seven continents . It is connected to the Central American Land Bridge to the north. In the east it is 2900 km from Africa , while the west coast is between 7600 km (Patagonia) and 11,000 km (northwest Colombia) from New Zealand . In the south it is about 900 km from Antarctica , with which it is genetically linked by a chain of islands.
Size and relief
South America extends over an area of 17.8 million km² and thus takes up 12% of the earth's surface. Its geological border with Central America is the Colombian river Río Atrato . The northernmost point is on the Colombian peninsula "La Guajira" just below 12 ° 30'N near the small community of Áirrainmaru. In the south the subcontinent extends to Tierra del Fuego , the southernmost point of which (just north of 56 ° S ) marks the uninhabited island of Hornos ( Cape Horn ), which belongs to Chile . The distance between these two points is over 7600 km. The South American continent reaches its westernmost extent in Cape Pariñas (81 ° 20'W), near the Peruvian city of Talara . The eastern counterpart to this is the Brazilian Cape Ponta do Seixas near the city of João Pessoa (approx. 34 ° 45'W). The east-west extension between these two points is over 5100 km.
A geological-morphological division of South America results in three large areas:
- The Andes as high mountains on the west side of the continent (up to 7000 m high)
- The river lowlands in the center and south of the continent (up to 500 m high)
- The mountainous region as a low mountain range on the Atlantic side (up to 3000 m high)
- The Andes are divided into three mountain ranges in the north: the western, central and eastern cordillera, which are delimited in a north-south direction by the rivers Río Atrato , Río Cauca and Río Magdalena . In the Colombian Sierra Nevada de Santa Marta , the northernmost branch of the Central Cordillera, the Pico Cristóbal Colón, only 45 km from the coast, already reaches an altitude of 5776 m.
- Further south, the Andes are divided into three parts. In Ecuador , the central part is called Sierra , the western part is called Costa and the eastern part is called Oriente . In between there is a plateau on which the capital Quito is located. In Peru the area of the central Andes begins, in which the east-west extension of the Andes increases towards the south and these are divided by several longitudinal valley furrows. In the Peruvian Cordillera Blanca , one of the highest points in America is reached at the top of Huascarán (6776 m). The Andes curve to the south and reach their greatest east-west extension in Bolivia (800 km). This area is characterized by a well-developed high basin ( Altiplano ), which stretches from southern Peru via Bolivia to Chile and Argentina. Here you can find numerous NS trending depressions with large salaries . On the western slope of the Andes there is one of the driest regions in the world: the Atacama Desert . In the north of Chile, a clearly recognizable division of the Andes (coastal cordillera and central cordillera) with a longitudinal depression emerges again. This dichotomy can be seen up to the southern end of the continent. The highest mountain in America, the Aconcagua (6961 m), is located between the two cities of Santiago de Chile and Mendoza .
- Towards the south the Andes quickly lose height and south of the 50 ° S only rarely reach heights above 2000 m. Finally, south of Tierra del Fuego, the Andes descend into the sea. The southernmost point of Chile is formed by the Diego Ramírez Islands about 100 km south of Cape Horn.
- The lowlands of South America can be sharply demarcated morphologically from the high mountains of the Andes. Its average height is 200 m and only in a few exceptions (Sierra de la Macarena / Colombia or Sierras de Córdoba / Argentina ) is the lowland still dominated by mountain ranges with heights of over 2000 m. The lowlands can be divided by its widely branched river systems. In the north runs the Río Orinoco (2500 km length), whose catchment area covers an area of approx. 1,000,000 km². Subsequently to the south is the 7,000,000 km² catchment area of the 6500 km long Amazon .
- The river systems of the Río Paraná and Río Paraguay with a length of 4700 km and an area of influence of 3,700,000 km² are located approximately below 15 ° S. These two rivers flow through the La Plata countries Paraguay , Uruguay and Argentina. In the estuary of the Río Paraná and Río Paraguay, both rivers merge to form the Río de la Plata .
- Approximately between 20 ° S and 30 ° S is the Gran Chaco lowlands (heights between 100 and 300 m) in which the countries Paraguay , Bolivia and Argentina have a share. The Gran Chaco merges to the south into the Patagonian lowland, which is cut by rivers running through EW. Although the Gran Chaco also represents a striking lowland, it is referred to in the specialist literature as the sub- Andean molasse basin and is therefore already part of the Andean system.
- The mountainous country (also known as the Brazilian mountainous country ) on the east coast of South America is, due to the lack of recent mountain formation, heavily truncated and less pronounced than the Andes on the western side. It also broke into several separate clods.
- In the north ( Venezuela , Guyana and small parts of Brazil), this includes the over 2500 m high table mountainous Gran Sabana (also known as the "mountainous country of Guyana"). Here is the highest mountain in South America outside the Andes, the Pico da Neblina with a height of 3014 m. This is separated from the Amazonassenke from the " Brazilian mountainous country " further south . Here you can find a variety of mountain forms that characterize parts of Brazil and Uruguay. To the south of the Río de la Plata one can only find the remains of the basement mountains of the Sierra de Buenos Aires , consisting of the Sierra de la Ventana with the Cerro Tres Picos (1239 m) as the highest elevation and the Sierras del Tandil .
Geology and geomorphology
South America as part of the Gondwana continent
South America was part of the ancient Gondwana continent until the Cretaceous . This meant that the east coast of today's South American continent was connected to the west coast of Africa (Nigeria / Cameroon - South Africa) from the height of the Brazilian cities of Fortaleza-Recife to at least the mouth of the Río de la Plata . The area of today's continental margins must have been a tectonic weak zone even before the Cretaceous, which began to break up from south to north in the transition from the Lower Jurassic to the Upper Cretaceous.
The formation of the South Atlantic was accompanied by strong volcanism, the flood basalts of which can still be found in Africa (Karru volcanic rocks), India (Dekkan-Trapp) and South America (Paraná basalt). The Paraná basalts cover an area of over 1,200,000 km² in the countries of southern Brazil, Uruguay, Paraguay and northeast Argentina. This makes it the largest lava plateau in the world. One of the most famous manifestations of these Cretan ceiling basalts are the Iguazú waterfalls on the border between Brazil and Argentina. Here, huge masses of water tumble over the basal edges of the Serra Geral formation .
The Jurassic-Cretan volcanism, which is responsible for the formation of the Paraná basin, can be divided into three sequences:
- Basalts : 150 - 130 mya
- Intermediate volcanic rocks : 130 - 123 mya
- Rhyolites : 125 - 118 mya
In between there were periods of rest, which can be seen from the intermediate layers of sandstone. Overall, the Paraná basalts reach a maximum thickness of up to 1,800 m with an average thickness of 50 m per layer.
The increasingly acidic volcanism is explained by intra- and pericratonic processes, which led to the melting of the surrounding crustal rock (this process is also known as anatexis in geology ).
The final separation and thus the final end of the ancient continent " Pangea " took place around 100 million years ago in the Middle Cretaceous.
In connection with the further opening of the South Atlantic, which was probably the result of a “ hot spot ” or a thermal diapir , alkaline and effusive volcanism again occurred on the northeastern edge of the Paraná Basin between 90 and 60 mya . However, this volcanism no longer produced flood basalts , but only intrusive and extrusive conical rock bodies. The niobium deposits in Araxá in Minas Gerais that were created in connection with these processes are even of global economic importance. The now passive continental margins of South America and Africa experienced severe subsidence and partial rift formation in the following years.
The extra-Andean space
The Precambrian shields and cratons
In South America there are two larger and one smaller Precambrian units ( shields and cratons ). The two larger ones include the Guyana craton in the north (see also chapter "Size and Relief"), which is around 1.8 billion years old, and the cratons in Brazil, which are only around 600 million years old. A smaller craton can be found in Uruguay (Rio de la Plata-Kraton), the oldest series of which are 2.1 billion years old.
In general it can be said that the knowledge of the South American Precambrian compared to other shields and cratons on earth is still very thin. The reasons for this are the sometimes difficult accessibility and the deep weathering that takes place.
The Guyana Craton
The Guyana craton is the largest closed ancient core on the South American continent. It stretches between 9 ° N and the equator over the states of Colombia, Venezuela, Suriname, Guyana, French Guiana and Brazil over an area of 4.5 million km².
The last orogenesis occurred in the Upper Paleoproterozoic about 1.9 billion years ago. All later tectonic processes no longer influenced this region. In said orogeny, the current strike direction was also generated in the WO direction (from Venezuela towards French Guiana), due to which the Guyana craton differs significantly from the Brazilian cratons, which strike in the Nazi direction.
The formation of the Guyana craton is influenced by four archaic events (named after local places):
- Guriense: 3.4 - 2.7 bill. A
- Pre-Transamazonico: 2.4 - 2.1 bill. A
- Transamazonico: 2.1 - 1.7 bill. A
- Paraguayan: 1.7 - 1.4 bill. A
The oldest part of this archaic base can be found in a narrow WSW-ONO band on the edge of the Orinocos. Here you can find highly metamorphic gneiss , gneiss- granite , granulite or amphibolite . Some of these ancient rocks are very rich in iron, which explains the fact that the largest metal concentrations in South America occur over the oldest granulite gneisses in the form of itabirite series.
During the pre-Transamazonico, regional metamorphosis led to the formation of greenstone belts , which are typical of kratons.
However, during the Transamazonico event, a magmatic phase, the greenstone belts were repeatedly broken by acidic (silicon-rich) volcanic rocks . In addition, there were numerous granitic intrusions from the time between 2.1 and 1.9 billion years. Thereupon the Imataca-Pastora block that had been created in the Guriense broke and disintegrated into individual basins .
The molasse-like , terrestrial Roraima layers were formed in these basins between 1.7 and 1.6 billion a . They extend over an area of 1,200,000 million km² and are hardly tectonically disturbed and not metamorphic to this day. Several sediment packages (especially sandstone ) form mighty high plateaus in the area today. The Cerro Roraima (2772 m), located on the border between Venezuela, Guyana and Brazil, is one of the highest peaks in the Guyana craton with the Pico da Neblina (3014 m). The undisturbed sedimentation of the Roraima layer is good evidence that the Precambrian deformation history was already over here .
The Paraguazense event is marked by (anorogenic) granite intrusions that are not associated with mountain formations, especially in the period between 1.6 and 1.3 billion years. These sometimes formed large batholiths , which are particularly noticeable in the west, in the border area with Colombia.
Brazilian shield
When speaking of the Brazilian shield, one has to say more precisely that the Brazilian Archean is characterized by several nuclei. These old cores were welded with several folds in the Proterozoic (2.6 - 0.57 billion a), so that, in contrast to the Guyana craton, no rocks over 3 billion years old are found here. The most important event for this shield was the aforementioned Transamazonic orogenesis, during which about 1.9 billion years ago all older layers were deformed. The middle to young Proterozoic fold belts that separate the individual nuclei were formed between 1.5 and 0.5 billion years ago. A final stabilization of the Brazilian shield therefore only took place at the beginning of the Paleozoic Era.
Río de la Plata Kraton
This little sign is in the south of Uruguay and separates into two blocks. The older of the two dates from between 2.2 and 1.9 billion years ago and is largely hidden under the Gondwana layers of the Serra Geral. Hence, very little is known about him. The younger of the two consists of an older (900 million years old) layer of basaltic lava and granite and granodiorite can be found in the hanging wall (600 million years old). The conclusion of the Brazilian cycle means the final consolidation of the shields outside of the Andes for South America. Further Precambrian nuclei can be found in the "Sierra de Buenos Aires" and in the "Sierra de Córdoba".
Phanerozoic sediment cover
The end of the Precambrian in South America is marked by the formation of large basins that were or will continue to be filled with sediments in the course of the Phanerozoic , and which in fact have not undergone any deformation since then. The sediments themselves are largely terrestrial-fluvial. Sea advances were only made briefly. The main phases of sedimentation took place mostly in the Devonian and Carboniferous. Three large basins can be differentiated:
- Amazon Basin (1,250,000 km²)
- Parnaiba-Maranhao Basin (650,000 km²)
- Paraná Basin (1,200,000 km²)
Amazon basin
The Amazon basin is 3500 km long and 300 to 1000 km wide. It is crossed from west to east by the Amazon which gives it its name (see size and relief). The Amazon basin is almost completely covered with rainforest and is in turn divided into three sections:
- The upper Amazon basin is bounded in the west by the Andes and in the east by the confluence between the Rio Negro and the Rio Solimoes near Manaus . This area can only be counted in the Upper Carboniferous part of the Paleozoic sedimentation area of the Amazon basin.
- The middle Amazon basin is a narrow WO furrow. It ends in the east at the tributary of the Rio Xingu . The tributaries of the Amazon are characterized in this area by rapids and waterfalls, which is related to the erosion of the Paleozoic series in the north and south of the basin.
- The lower Amazon basin finally means the estuary. The narrow area of the central section widens in a funnel shape into various mouth arms around the island of Marajó.
Structurally, this classification also corresponds to the three proven thresholds in the Amazon basin. The Iquitos threshold runs east of the Peruvian city of Iquitos , the Purús threshold west of Manaus, where it separates the upper and middle basins. The Gurupá threshold runs east of the Rio Xingú and separates the middle from the lower basin.
The middle Amazon basin also has a trench structure that can be extended to the mid-Atlantic ridge .
The history of the deposits in the Amazon basin begins in the Ordovician and continues to this day. Particularly thick deposits have been handed down from the carbon (sandstones, claystones, limestones, evaporites). However, for most of the Mesozoic Era, sedimentation was interrupted and erosion prevailed. It was not until the Upper Cretaceous that continental series were found in the central Amazon basin. The Cenozoic sediments are again more important for the filling of the Amazon basin, especially in the river plains and in the estuary delta. A special feature of the Amazon basin is that its sediment filling in the west of the basin, near the Andes, has experienced a certain degree of tectonic deformation.
It is also particularly noteworthy that the Amazon basin drained into the Pacific west of Iquitos until the Younger Tertiary. This was prevented in the Miocene by raising the Andes.
The Paranaiba Maranhao Basin
The Paranaiba-Maranhao Basin extends in an almost circular shape in NE Brazil. Its center is in the state of Maranhão . There it forms a spacious plateau into which several rivers have cut. The most important river, the Rio Paranaíba , does not form the central axis as in the Paraná Basin or the Amazon Basin. This is due to a recent uplift of the eastern edge, which is why the hydrographic network in this basin has no center.
The sedimentation of this basin began in the Silurian , from where the most varied layers (sandstone, coal, limestone) were permanently formed. In contrast to the Amazon basin, the sedimentation history of the Paranaiba-Maranhao basin has ended since the Cretaceous period. Today erosion prevails there.
The Paraná Basin
The Paraná Basin strikes from north to south along the upper and middle reaches of the Río Paraná . The largest part of this basin is in Brazil, a smaller part in the west in Paraguay and in the south in Uruguay and Argentina. Some tributaries have their origin in the southern Bolivian Andes. Here, too, the oldest sediments are from the Silurian and here too there is no significant sedimentation in most parts of the basin. Characteristic of the Paraná basin is the extensive covering of the basin filling with flood basalts of the Cretan Serra-Geral formation (see South America as part of the Gondwana continent).
The Andes
The Andes are in clear contrast to the extra-Andean areas of Atlantic South America. As part of the Circumpacific Ring of Fire, they are among the most restless zones on earth. They are also a young mountain range, which distinguishes them from the Paleozoic sedimentation basins and the even older archaic cores.
Although they make a very uniform impression morphologically, they can be divided into three areas: Southern Andes (to Valparaiso / Mendoza), Central Andes (to the Peru / Ecuador border) and Northern Andes (to the Sierra Nevada de Santa Marta and Cordillera de Mérida ). According to current knowledge, it is becoming increasingly clear that there was neither a common geosyncline as the starting point for mountain formation, nor a folding that affected all parts of the Andes equally.
The northern Andes
The northern Andes are divided into two mountain ranges in Ecuador, while in Colombia they fan out into three ranges.
The northernmost foothills of the Andes are the Sierra Nevada de Santa Marta and the Caribbean coastal mountains of Venezuela. The Caribbean coastal mountains, which still reach heights of 2800 m south of Caracas , are a highly complex orogen of metamorphic rocks and deep-sea sediments. It is believed that the collision between the Caribbean and South American plates pushed up parts of the oceanic crust. The whole area here is characterized by numerous faults that have been active since the Tertiary and which explain the high earthquake danger in north-east Venezuela.
From a geological point of view, the Caribbean Coast Mountains are the extension of the Cordillera de Mérida , which in turn is the eastern branch of the Eastern Cordillera of Colombia. The western branch of the Eastern Cordillera is the Sierra de Perijá in Colombia. Both branches together frame the Maracaibo bay. In contrast to the more southerly Andes, no volcanic rocks have been mined here since the Paleozoic. These two branches were raised in the Eocene .
In Colombia the differentiation into three branches (western, central and eastern cordillera) can be clearly defined. The western cordillera is covered by basaltic volcanic rocks. The Central Cordillera is clearly distinguished from it (and also from the Eastern Cordillera). It was probably a high area in the Mesozoic Era. From the Miocene onwards , there was strong volcanism in this area, accompanied by the formation of stratovolcanoes . In the Eastern Cordillera, the Precambrian base is exposed in places, which is tectonically strongly folded. On top of them are huge Cretaceous sediments that were no longer recorded by any orogeny. The Sierra Nevada de Santa Marta is surrounded on all sides by young depression. It therefore rises as an isolated block ruggedly over the Caribbean.
In the south of the northern Andes, in Ecuador, the Andes are clearly differentiated into two strands: the Western Cordillera (Sierra) and the Eastern Cordillera. The Western Cordillera consists of an alternation between basaltic volcanic rocks and Cretaceous deposits, which, however, were heavily folded in the Tertiary. The valley of Quito, formed during the Tertiary, lies between the two Andes chains. This lies at an approximate altitude of 2500 to 3000 m and is characterized by pyroclastic and glacial deposits. During the Tertiary, other volcanoes formed, both in the Quito Depression and on the flanks of the Western and Eastern Cordillera. The Eastern Cordillera, on the other hand, consists almost entirely of metamorphic rocks.
The central Andes
The coastal cordillera (Cordillera Costal)
The coastal cordillera stretches south of Lima over the entire length of the Andes to the extreme south of South America. It rises partly as a steep coast and reaches its highest elevations in the Sierra Vicuña Mackenna near Antofagasta with over 3000 m. Overall, it was built over an old metamorphic base, which is still open in some places (e.g. in Mollendo and Arequipa in Peru). Between the Jurassic and the Cretaceous there was already the formation of basaltic and andesitic volcanic rocks as a result of an active continental margin. Plutons rose during the Upper Paleozoic as well as during the Jurassic and Cretaceous. Thus, the entire overburden of the coastal cordillera is strongly influenced by disturbances.
Long valley (Pampa de Tamarugal)
In the north of Chile between Arica and Copiapó , behind the coastal cordillera, the trench-like collapse of the Pampa de Tamarugal follows . Its internal structure is still largely unknown.
Precordilleras
Following the longitudinal valley (Pampa de Tamarugal) is the Precordillere, which is also restricted to this section and runs in the west of the High Cordillera. Its substructure consists of heavily folded Paleozoic series and above it of Mesozoic marine and volcanic deposits. In some places, all of the Jura deposits are marine.
High Cordillera / Western Cordillera
From Lima to approximately the level of Copiapós , the Western Cordillera is covered by Cenozoic volcanic rocks. Volcanic activity began here 25 million years ago and continues to this day, which proves the existence of hundreds of peaks between 5000 m - 7000 m. Between Copiapo and Iquique , between the Precordillere and the High Cordillera, there is another submerged piece of crust that forms a plateau with numerous large salars at an altitude between 2500 m - 3500 m. In the southern part of the high cordillera, the structure of the high cordillera is characterized by the ascent of plutons. The Aconcagua (6958 m), the highest mountain in America, is also located on the Argentine high cordillera .
Puna / Altiplano
The Altiplano (called Puna in Argentina ) extends as a broad subsidence field from northwest Argentina via Bolivia to Peru. In the Cenozoic, this part of the trench was sunk considerably compared to the surrounding cordillera. The average heights of the Altiplano are between 3500 and 4000 m; its surface is characterized, especially in the central and southern part, by the appearance of extensive salt pans (salars). There was also strong volcanic activity in the Miocene , which led to the formation of stratovolcanoes that tower above the Altiplano ( Queva (6130 m), Antofalla (6100 m) or Sajama (6520 m))
Eastern Cordillera (Cordillera Occidental)
The Eastern Cordillera begins parallel to the Altiplano in northwest Argentina and extends over Bolivia to almost the height of Lima. In some sections, even Proterozoic rock is exposed here. The main material of the Eastern Cordillera, however, are Paleozoic sediments, which were mostly heavily folded. Plutons also appear here, some of which are exposed. The most impressive examples of this are the Illampu and Illimani mountains near La Paz .
Cordillera Frontal (Precordillera)
The Cordillera Frontal is a mountain range that runs exclusively in Argentina. It begins at the height of San Miguel de Tucumán and is characterized by Mesozoic volcanism and Cenozoic continental sediments. Upstream of it is the Precordillere from La Rioja via San Juan to Mendoza as a separate mountain range . The marine Cambrian deposits are characteristic of this mountain range.
Sierras Pampeanas
The Sierras Pampeanas , which lie south of the Puna, run exclusively in Argentina (24 ° S - 36 ° S). In them the strongly folded and metamorphic Proterozoic basement is exposed. Individual blocks and clumps were raised between the Pliocene and the Pleistocene.
Sierras Subandinas
The Andean foreland again comprises the entire transition area between the cordillera and the lowlands of Peru, Bolivia and Argentina. The western part still consists of ranges of hills like the Voranden chains of Bolivia, which then slope more and more flat towards the east until they finally merge into the plains.
The southern Andes
The coastal cordillera (Cordillera Costal)
The coastal cordillera consists of a clump-like, raised hull that was eroded in the Cenozoic and covered by young sediments. From Tierra del Fuego to the south of the island of Chiloé , plutons have also penetrated the underground. The coastal cordillera loses its character as a mountain range south of the island of Chiloé, but appears 100 km further south in the form of countless small islands off the southern Chilean coast. The coastal cordillera is thus a relic from the Gondwana period, which was incorporated into the Andes but which is “foreign” to them.
The Long Valley (Valle Central)
The Chilean long valley already forms from 47 ° S in the local canals and runs clearly to Santiago de Chile. This is probably a rift valley that experienced different degrees of subsidence from north to south. An indication of this could be the Cenozoic sediments, which reach a thickness of 4000 m at Puerto Montt , while in the vicinity of Santiago only 500 m could be detected. The longitudinal valley is of course associated with a variety of vertical faults.
High Cordillera (Cordillera Central)
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South of Santiago, another elongated volcanic chain sets in with the 6,800 m high Tupungato volcano. It consists of a large number of highly explosive stratovolcanoes, which in turn were formed from andesitic to basaltic lavas. This 1000 km long chain of volcanoes quickly loses height in the south and extends roughly to 42 ° S south of Puerto Montt . From 42 ° S onwards, Mesozoic and Tertiary sedimentary overburden, which lie on top of the metamorphic basement, play a greater role than Cenozoic volcanism. In this zone there are only a few isolated volcanoes and the altitude of 3000 m is rarely exceeded. The Pleistocene glaciation with numerous glacial lakes, karen and fjords has a defining effect on the relief.
climate
Climatic conditions
The climate in South America is extremely complex. Year-round climatic influences are the cold Humboldt Current on the west coast of Peru, the intra- tropical convergence zone ITCZ, the formation of cyclones on the edge of the subtropical high pressure area and the trade winds .
The cold Humboldt Sea current causes the sea surface to cool off the coast of Peru and northern Chile, which leads to the formation of coastal deserts. This phenomenon is based on the fact that the cooled air leads to a constant inversion , thus to a stable high pressure area that does not allow convection and thus no precipitation. The effects are extensive desert regions on the coasts and fog formation near the sea surface.
The equatorial tropical location causes the formation of an innertropical convection zone over the central Amazon region in the southern winter, which leads to heavy rainfall. In the southern summer it shifts further south, so the inner tropics are characterized by year-round precipitation. Also in the southern summer a continental heat low forms , which (in the southern summer) is also rich in precipitation. The southern peripheral tropics are thus characterized by (southern) summer precipitation.
The northern peripheral tropics are characterized by trade winds in the east (high precipitation all year round) and by cool sea water on the coast in the north (very little precipitation). The south trade winds on the east coast lead to increased precipitation in the coastal regions. In the southern summer characterized by the formation of monsoonal easterly winds and in the southern winter by accumulated precipitation on the coastal regions.
The stable high pressure system on the western edge of South America in combination with the cold air masses of the southern polar regions leads to the formation of cyclones off the coast of western Patagonia. The cyclonic fronts vary in their location in southern summer and southern winter. The shift to the north in southern winter leads to periodic winter precipitation in the south of Chile as well as to sporadic winter precipitation in central Chile. In return, the shift in the cyclonic fronts in the southern summer (influenced by the changed position of the ITCZ) leads to pronounced summer drought in all of central and southern Chile as far as Patagonia.
The cyclonic fronts form heavy rainfalls on the Andean luv side of the Patagonian mountains, which can be described as hypermaritime and occur all year round. The Chilean part of Patagonia has very high rainfall all year round. The Andean lee side of Patagonia (Argentina) is characterized by drought. (see ENDLICHER 2005).
Vertical climatic differences
The Andes themselves have a further climatic subdivision in the vertical dimension. Thus, they can be divided into 5 height levels. The Tierra Caliente (warm earth, up to 1000 m), the Tierra Templada (temperate earth, up to 2000 m), the Tierra Fria (cold earth, up to 3500 m, cultivation limit and frost limit), the Tierra Helada (icy earth, up to 4500 m , Snow line) and the Tierra Glacial (glacial earth, up to 6000 m, anecumene).
Glacial occurrence
There are also glaciations in the Andes . The largest innertropical glaciers in the world can be found in Peru. In Patagonia there is extensive inland glaciation and tongue glaciers that reach down to sea level. Glaciers occur in areas where there is sufficient year-round low temperatures and correspondingly high rainfall at high altitudes.
El Niño
A significant climate phenomenon for South America is the El Niño phenomenon ( El Niño , the Christ Child). This is not, as is often wrongly used, a climatic, but a purely oceanic phenomenon. The cold water flows off South America break up and warm water collects off the South American coast. As a climatic consequence, the normally prevailing stable high pressure situation is canceled out and the Walker circulation is reversed (between South America and Indonesia, parallel to the longitude). This reversal has serious consequences, since the warm water off the coast leads to a drastic death of the normally cold water-accustomed sea creatures and heavy precipitation occurs on land. The landscape, which is otherwise characterized by drought, can be severely damaged by such heavy precipitation events (slide, mudslides, etc.).
Individual evidence
- ↑ See Kley et al. 1991
literature
- W. Zeil: South America . Stuttgart 1986.
- J. Kley et al .: The central Andes . In: Geographische Rundschau, Vol. 43, No. 3, 1991, pp. 134-142.
