GEOG 3515

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GEOG 3515

• The Geography of South America

Class 4 Landscapes and Landforms
Music Map
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Physical Geography - East v West

• Geologists contrast the eastern portion of South
  America with the Western portion.
• The east is representative of a spreading plate
  boundary (old, hard rocks capped and fringed by
  newer sediments and more eroded mountains
  Brazilian Highlands, Guiana Highlands, Patagonia
  Plateau).
• The west is typical of a colliding plate boundary
  (newer hard rocks and recent volcanics with high,
  youthful mountain ranges undergoing significant
  readjustment Andes continuing up into Central
  America).
• Between them is a great trough of lower land that
  was once covered by shallow seas and which now is
  divided and drains to the Atlantic to the north,
  east and south by three vast rivers the Rio
  Orinoco, the Rio Amazonas and the Rio Paraná.
• To the north is the complex Caribbean Sea system
  where multiple crustal plates coalesce.

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Physiographic Regions

• From this map, it is easy to see the arrangement
  of the highland plateaus, the high Andes and the
  intervening river systems of the Orinoco, Amazon
  and Paraná.

Map Credit David Hardin, Longwood Univ.
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South America and Central America

• The forces of continental drift, plate
  subduction, and tectonic rippling and uplift has
  played a major role in forming the South American
  and Central American mountain landscape, part of
  a larger phenomenon called the Pacific Ring of
  Fire.
• Volcanic activity and crustal uplift at the
  junction of several different subducting plates
  North American, Caribbean, Pacific, Cocos and
  Nazca, have all contributed to Western South
  America and Central Americas mountainous
  character - what geologists refer to as the
  Western Alpine system that formed the Andes.
• This is clearly seen by looking at a map of the
  major plates and their patterns of movement and
  interaction.

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Plate Tectonics

• Interactions of the different plates and their
  migrations have caused many of the main
  physiographic features.

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Caribbean islands

• The Caribbean islands owe their existence to the
  two different sets of geological forces acting on
  the region.
• To the north, folding and faulting of layers of
  limestone that once were laid down in shallow
  seas over the American and Caribbean plates have
  thrust the rocks upward out off the coast of
  Mexico and Central America.
• To the south, arcs of Volcanoes have sprouted up
  along the edge of the Caribbean plate as it has
  been impacted by the larger and faster moving
  South American plate and as magma has burst
  through the ruptured surface of the earths
  crust.
• This can best be seen by looking at a
  physiographic map of Middle America that captures
  this dynamic geological and geomorphological
  arrangements.

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Physiography of Central America and the Caribbean
Sea

• Colliding and rubbing plates have led to buckling
  and shearing of the earths crust.

Map Credit David Hardin, Longwood Univ.
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Brazilian Highlands

• Attributes
• Covers 1/3 of Brazil
• Old metamorphic and igneous rocks covered with
  sediments
• 600-900 m (2,000-3,000ft) ASL
• Three main elements Serra do Mar coastal
  escarpment, Sertão/Paraná Plateau, and Mato
  Grosso Plateau.

• Importance
• Acted as a barrier to early settlement of the
  interior
• Contains some of the worlds richest ore deposits
  - esp. industrial metals (Serra do Mar, Mato
  Grosso).
• Has vast agricultural potential (humid Paraná
  Plateau)
• Has fabulous water falls and hydropower potential
  as rivers tumble over volcanic layers (Sertão)
• Forms much of the significant headwaters of the
  Amazon river (Mato Grosso).
• Is a powerhouse of heavy industry (Mato Grosso)

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Images of the Brazilian Highlands
Canyons of the Sertao/Parana Plataeau
Serra do Mar escarpment
Table lands of the Sertao/Parana
Plataeau developed for farming
Mato grosso Plateau eroded table Mountains and
intervening valleys.
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Guiana Highlands

• Attributes
• Isolated extension of Brazilian Highlands
  (similar geology)
• Many rivers and waterfalls
• More tropical with considerable precipitation,
  lush rainforests, and fertile river valleys.
• Many isolated mountain tops and small plateaus

• Importance
• Contains worlds highest waterfall Venezuelas
  Angel Falls
• Hydropotential largely untapped due to
  inaccessibility
• Region of as yet largely undisturbed ecological
  and cultural heritage
• Selective pockets of destruction from gold,
  diamond and mineral ore mining to the north.

Angel Falls
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Central Lowlands

• Attributes
• Interior plains stretching down 52? of latitude.
• Character varies with climate from N to S.
• Represent troughs formed between the old eastern
  mountains and the new Andean range.
• Filled with marine and alluvial sediments.
• Well watered by rivers draining off highlands.
• Generally low-lying land and slow moving rivers
  with gradual slopes except when cutting down over
  scarps.

• Importance
• Depending on climate, will have different
  agricultural uses, from tropical plantations to
  temperate wheat fields to livestock grazing.
• In the north, contains considerable oil trapped
  in folded marine sediments.
• Has been developed where river navigation
  facilitated early transport systems.

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Llanos (Orinoco River Floodplain)

• Attributes
• Used to be an ocean-filled trough now ASL.
• Sediment has poured in to the upper ends as the
  Andes have eroded, creating a gently sloping,
  monotonous plain like a bigger version of the CA
  Central Valley.
• Holds the 2,600km (1,600 mile) long Orinoco
  River.

• Importance
• Will yield much of the oil wealth of Venezuela
  and Colombia
• Extensively grazed for the production of beef
  cattle (for export mostly Zebu/Brahma crosses)
• Sparsely populated above Ciudad de Bolivar due to
  inaccessibility

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Images of the Llanos
Extensive grazing on vast grassy plains
Vast vistas of grass and scrub
The Orinoco widens toward the ocean
Flatlands frequently flood in monsoons
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Amazon Plain

• Attributes
• Lowland portion of the worlds biggest river
  system that cycles some 20 of the worlds
  freshwater to the Sea.
• Drained by over 1,100 different rivers tributary
  to the main Rio Amazonas.
• Stretches all the way through Brazil into
  Venezuela, Colombia, Ecuador, Peru and Bolivia
  where relatively small plateaus divide it from
  the Llanos and the Gran Chaco systems.

• Importance
• Contains 1/3 of the worlds remaining tropical
  rainforest.
• Called the worlds lungs due to the immense
  carbon dioxide fixing that takes place.
• Amazon is deep enough to allow ocean liners to
  sail 1,600 km (1,000 miles) up river to Manaus.
• Home to immense tropical diversity and a variety
  of indigenous peoples.
• Becoming increasingly populated and developed

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The Amazon Basin
Meandering tributaries through the dense Selva
Jungle grows to the rivers edge
Indigenous peoples still inhabit the region -
xingu
Typical town on the river (Tefa)
Mixing of waters from tributaries with different
geologies
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Andes Mountains

• Attributes
• Part of the Western Alpine system formed at the
  edge of the Ring of Fire
• Older rocks, sediments and intrusive volcanics
  have been folded, faulted and thrust upwards to
  as much as 7,000 m (23,000 ft)
• Volcanic peaks dominate the landscape, often
  separated by high, wide valleys, some with lakes
  or internally-draining rivers that evaporate to
  salt ponds.

• Importance
• Many of the valleys are filled with fertile,
  well-watered volcanic ash and alluvial soils
  excellent for agriculture.
• Minerals are/were found in many areas including
  precious metals like gold and silver and others
  like tin and copper
• Soil erosion is intense and the ancient peoples
  built incredible terrace systems to allow them to
  farm on the high slopes.

To be continued
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Images of The Andes
Wide high valleys intersperse the peaks often
grazed by alpacas, vicuñas and llamas
Home of the Inca empire with mega-cities like
Machu-Pichu
High volcanic peaks tower from the range up to
more than 20,000 feet.
Soils were stabilized and flat strips of land
created for farming by terracing.
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The Southern Andes

• Attributes
• One of the most physically impressive and
  geologically active regions in the world.
• Increase in elevation toward the north 8,000 ft
  in Tierra del Fuego, 13,000 ft in Southern Chile,
  23,000 ft in Central Chile.
• Glaciers have sculpted the mountains in Central
  Chile, creating vast Fjords and running water has
  laid down vast alluvial fans.
• Folding of rocks has created a vast central
  valley, part desert, part fertile plains, part
  mineral zones.

• Importance
• Fjords are increasingly used for fish farming
  salmon for the international market.
• Commercial agriculture in the region satisfies US
  demand for year-round summer produce.
• Nitrate deposits for commercial fertilizer are
  mined in alkali sinks that occur in interior
  basins.
• Copper deposits are vast in alluvial outwash fans.

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Southern Andes
Coastal fjords
Mountain copper mines
Farmed salmon
Lowland farming
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The South Central Andes

• Attributes
• Interior plateaus become frequent as the Andes
  widen in Bolivia, Peru and Ecuador punas and
  salares.
• Two parallel ridges (Cordilleras Real and
  Occidental) are divided by a vast high plateau
  the Bolivian Altiplano home of the Aymara
  Indians and covered with glacial outwash debris.
• Lake Titicaca, the fabled Incan navel of the
  earth, is the dominant feature of this region.
• The eastern slopes and lowlands are very warm and
  humid.

• Significance
• Aymara Indians fish and farm the cold and
  desolate Altiplano producing wool, potatoes,
  coca and other crops for sale.
• The northern Yungas are a key coca growing area.
• Bolivia generates some international income from
  silver and tin mines.
• Peru does likewise with extensive copper
  deposits.
• The north and eastern slopes drain to the Amazon
  basin.

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South Central Andes
Coca farming
Lago Titicaca
Aymara produce
Highland farms
Fishing the lakes
The Cordillerra Real and Altiplano
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The North Central Andes

• Attributes
• The Andes narrow again into Ecuador and Colombia
  to form a double volcanic ridge with a narrow
  rolling trough the Callejón Andino.
• Averaging around 2,000-3,000m (7,000-10,000 ft),
  the ridges are interspersed by high peaks up to
  almost 6,000 m (20,000 ft).
• The trough is divided into ten fertile and basins
  full of fertile ash and alluvium.
• The eastern slopes have oil and natural gas
  trapped in folded and faulted rock strata.

• Significance
• The high basins are well populated and, in
  Ecuador, home of the nations capital Quito.
• The Peruvian and Ecuadorian coastal plains are
  terraced and farmed with irrigation water drawn
  from the west-draining Andean runoff.
• The coastal mangroves have been cleared in many
  places for shrimp farms.

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North Central Andes
Ecuadors mangroves are stripped for
shrimp Farming exports are almost 1billion
annually
Oil exploration site in Ecuadorian Amazon
Quito occupies a highland basin in the callejón
Cotopaxi dominates the skyline
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The Northern Andes

• Attributes
• In Colombia, the Andean Cordillera together and
  then break into three parallel ranges with
  lowlands to the west, north and south.
• Two big north-south rivers, the Cauca and the
  Magdalena, drain to the Caribbean sea.
• Further east, more fertile, well-watered valleys
  predominate, one of which is home to Bogotá.
• The Andes finally trend north and east into
  Venezuela, splitting and draining to the
  Maracaibo basin on one side, and the Orinoco on
  the other.

• Significance
• Sediments trapped in the Caribbean Sea region
  yield oil and natural gas in and around Maracaibo
  and in the interior forests of Colombia.
• The Colombian highlands, especially around
  Medellin, have many coca plantations and are the
  base of drug smuggling routes up through the
  Caribbean sea.
• The long, gentle river valleys have been used as
  rail and river transport arteries for centuries.

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Northern Andes Region
Bogotá
Maracaibo oil
Coca plantation
The low Andes
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Some final observations on the Andes

• Reading about South Americas diverse and
  awe-inspiring landscape, one sees how different
  situations have often governed patterns of human
  development.
• Recent uplift and the formation of alpine
  glaciers has led to extensive landform change,
  erosion and deposition, that created pockets and
  ribbons of good agricultural opportunity these
  have been extensively exploited.
• Erosion of rocks has led to extensive placer
  deposits of minerals, as has the accumulation and
  evaporation of mineral-rich runoff these have
  been mined in many areas.
• Even in high elevations, combinations of good
  soils and water have led to extensive settlements
  that have persisted for 500 years.
• Where minerals led commercial and artisan centers
  to form on more forbidding slopes, food
  production required massive terracing to
  compensate for a lack of flat land.
• Relative isolation has been used to good
  advantage for one modern cash-crop, the coca
  plant, which is widely grown in the Central and
  Northern Andean region.
• The Andes provided the modern world with one of
  its staple foods the humble potato.