Amazon Basin


Also found in: Dictionary, Wikipedia.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Amazon Basin

 

or Amazonia, in South America; the largest lowland on earth, with an area of more than 5 million sq. km.

The basin extends from the Andes to the Atlantic Ocean, between the Guiana and Brazilian plateaus in the basin of the Amazon, the largest river in the world in volume. It is situated in the geosyncline of the South American craton, which is mainly filled with Paleozoic marine and Mesozoic-Cenozoic continental deposits. The climate is hot (mean monthly temperatures 24–28° C) and moist (precipitation 1,500–3,000 mm and more per year).

Western Amazonia is a very broad (up to 1,600 km), level, and low-lying plain. The climate is equatorial and constantly moist. The rivers flow slowly in weakly incised broad valleys; these rivers are meandering and turbid (Rio Branco). The flat surfaces of the stream divides—the so-called terra firme (“hard earth”)—are covered by rain forests (selva, or hylea) on podzolic lateritic soils. In the river valleys, flood plains (várzea) and intermittently drowned and low delta (igapó) landscapes are distinguished; the latter are regularly submerged for several months. The várzea vegetation is similar to the eté and includes an especially large number of palms; rubber trees, or Hevea; kapok, or sumaúma (Ceiba); and cacao. The igapó vegetation is very sparse; imbaubal Cecropia is characteristic. Animals adapted to an arboreal life—including New World monkeys, sloths, and anteaters—are typical of the Western Amazon hylea. The land animals include giant armadillos, tapirs, and peccaries. There are also many birds, reptiles, amphibians, fishes, insects, and ants.

Eastern Amazonia (east of the mouth of the Rio Negro and Tapajós) is considerably narrower (up to 350 km). Marine Paleozoic and crystalline Precambrian rocks outcrop along the margins while the central portion has undergone recent subsidence, as a result of which the surface is intensely dissected, with buttes up to 350 m high; the rivers are straighter and deeper, with estuary-like mouths, many rapids, and transparent water that is darkened by decomposing vegetation (the Rio Negro). The climate is sub-equatorial. From June to September trade winds blow southeastward from the Brazilian plateau and cause droughts. This causes a considerable number of barren spots and savanna patches on red soils in the deciduous forests. Only bands of várzea and igapó on alluvial soils remain evergreen. Animals typical of open spaces make their appearance: these include brockets, anteaters, small armadillos, many rodents, and termites.

The Amazon lowland is very sparsely populated. Rivers are the basic paths of communication; along them are small settlements and two large cities—Manaus at the mouth of the Rio Negro, and Belém at the mouth of the Para River; a highway has been built between Belém and Brasilia. Manganese ore, discovered in 1945 (Serra do Navio in Amapa), nearby iron deposits, and oil fields in the lower Madeira valley (at Nova Olinda) are being developed.

REFERENCE

Lukashova, E. N. Iuzhnaia Amerika. Moscow, 1958.

E. N. LUKASHOVA

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Nearly 1,500 of the new fires were in the vast Amazon basin.
Since coming to power in October 2018, the president of Brazil has made no secret of his disdain for environmentalists and their efforts to save the vast tracts of the Amazon basin from development.
Wildfires have increased in Mato Grosso and Para, two states where Brazil's agricultural frontier has pushed into the Amazon basin and spurred deforestation.
Reports added that 15 people had been hurt in Ecuador, where power-cuts were reported in parts of its Amazon basin region.
Project implementation: Catch Amazon river dolphins throughout the Amazon basin to examine and GPS-tag them, gather data to determine how threatened they are, develop strategies to protect them
Tigre evaluates the unique international agreement among the South American nations of the Amazon Basin to form a legal stewardship arrangement for their shared environment, and looks at the prospects for regional law and international cooperation to define sustainable development in Amazonia.
Scientists have discovered the world's first so-called fluorescent frog in the Amazon basin in Argentina.
The project team determines soil respiration and soil chemistry on terra firme (non-inundated land), always juxtaposing forested land with post-forest land use in the Amazon basin. Key issues are oxygen production, biodiversity hotspots, water recycling, climate system tipping elements.
However, much of the Amazon basin is rich in oil reserves.
Among rainforest areas, the Amazon basin is of particular interest in this context because it influences precipitation and carbon cycles at global and regional scales (Cox et al., 2008).
The Dubai Rainforest is planned to recreate the natural environment experienced in the heart of the deepest rainforests, which cover 6% of the earth's surface with plant species chosen in collaboration with experts in the flora of the Amazon Basin.
An average of 27.7 million tons of dust per year -- enough to fill 104,980 semi trucks -- fall to the surface over the Amazon basin. The phosphorus portion, an estimated 22,000 tons per year, is about the same amount as that lost from rain and flooding.