The Natural Environment of South America

1
The Natural Environmentof South America

• Ecological Variety
• Landforms Origin and Development
• The Climate of South America
• The Water Resources of the Continent
• Plant and Animal Life

2
Ecological Variety

• South America is largely tropical (2/3)
• Abundant precipitation (rain)
• Broadleaf evergreen forests (lowlands and hills)
• Large environmental diversity
• Temperate southern cone
• Worlds major freshwater river system
• Amazon Basin

3
Ecological Variety - 2

• Abundance of rain
• Global wind circulation
• ITCZ, Easterly Trade winds, Hadley cell
• Ocean currents
• Warm currents
• Areas of droughts
• Subtropical highs
• Orography
• Ocean surface temperature
• Most of the continent is occupied by hilly
  uplands (highlands) and lowlands

4
Ecological Variety - 3

• Andean Cordillera
• Western edge of the continent
• Worlds longest mountain range
• Ecosystems
• Rain forest
• Desert
• Grassland
• High mountains
• Coastal systems

5
Landforms Origin and Development Major landforms

• Highlands
• Guianas
• Brazil
• Patagonia
• Central lowlands
• Andean mountain chain or cordillera

6
Landforms Origin and Development Major landforms

• South American Core Fig 2.1
• Three shields (areas of very old exposed rocks)
• Guiana shield
• Brazil shield
• Patagonia shield
• Elevation between 200 and 1500 meters
• Similar to continental shields of Africa,
  Australia and India
• Paraná lava flow Southern Brazil, Uruguay and
  Argentina

7
Landforms Origin and Development Major landforms

• Continental interior
• Lowlands
• Elevation below 200 m
• Formed by young sedimentary rock
• Orinoco lowlands (llanos)
• Amazon lowland
• Pantanal
• Chaco
• Pampas

8
Landforms Origin and Development Major landforms

• Andes Mountains
• Extends from Venezuela to Tierra del Fuego
• Extensive areas of recent volcanic rocks
• Frequent earthquakes
• Aconcagua highest mountain in the Western
  Hemisphere 6,960 meters
• Peru-Chile trench SA west coast
• Bartholomew Deep 8,064 meters deep off the
  Chilean coast.

9
Landforms Origin and Development Shields and
remnants of Gondwanaland

• South America rides on South American Plate
• South American Plate is currently moving westward
  Fig 2.2
• Nasca Plate is diving under S.A. (subduction) and
  causing the continuos uplift of the Andes
  Mountain
• Gondwanaland - Fig 2.3
• South America, Africa, Antarctica, Australia and
  India were clustered 180 Ma ago

10
Landforms Origin and Development Shields and
remnants of Gondwanaland

• Evidences of early connection
• Oldest parts of the shields (craton) are over 2
  billion years old
• Banded iron ore deposits in N and NE S. A. were
  created by the same ore-forming process of those
  in the Urals and Minnesota
• Mountain-building episodes similar in NE Brazil
  and eastern Paraguayan hills.
• Similar mountain system developed in Southern
  parts of S.A. and Africa 260 Ma ago.

11
Landforms Origin and Development Paraná Basalt
Plateau

• Part of the break-up process of Gondwanaland
  outpouring of lava
• Deccan lava flow in India
• Paraná basalt plateau between Brazil and Africa
  Cretaceaous period, 130 Ma ago Fig 2.4
• Terra roxa red fertile soils originated from
  weathering of the Paraná basalt.

12
Landforms Origin and Development Ancient Seas
and Sedimentary Rocks

• Cretaceous period
• Conditions were favorable for the formation of
  extensive oil deposits in Northern boundary of
  Gondwanaland
• Warm sea extended from present Indonesia, Persian
  Gulf, Libyan region to Gulf of Mexico and the
  Caribbean Sea.
• Tertiary period (60 to 3 Ma ago)
• Ocean waters invaded northern S.A.
• Trinidad, Venezuela, Colombia, E. Peru and
  Magellan Strait region
• Created shallow seas (organic sediments
  accumulation)
• Basis of large oil and natural gas deposits
• Amazon Basin (marine species) isolated when
  passage to the open sea was blocked to the N and
  W.

13
Landforms Origin and Development Island Arcs and
Land Bridges

• Early Tertiary
• NA and SA developed differently because they were
  separated by a large body of water
• Subduction raised volcanic island arc between NA
  and SA, creating an island bridge (about 60 Ma
  ago)
• This island bridge eventually drifted
  northeasward, forming the Great Antilles
• Later another subduction in the Pacific created a
  second volcanic island arc, moving northeastward
  into the gap between NA and SA (Fig 2.6).
• The great exchange

14
Landforms Origin and Development Island Arcs and
Land Bridges

• Galápagos Islands last 4 to 5 Ma
• Volcanic basalt, northern edge of Nasca Plate
• Overlies hot spot, causing frequent volcanic
  eruption and island formation
• Active Tertiary volcanism in the Andes
• Ash and scoria deposit tephra
• Covered high mountain depressions
• Transported by winds and fluvial erosion to the
  west coastlands, the Amazon basin and the Pampa
• Soils rich in siliceous cinders and bases
  (Sodium, Potassium and Calcium)
• Volcanism still active in Colombia, Ecuador,
  Peru, Bolivia Chile

15
Landforms Origin and Development Glaciation and
Recent Geological History

• South America present outline end of the
  Tertiary period 3 Ma ago.
• During the Quaternary period, last 2.5 Ma,
  present topography shaped mainly by glaciation
• Snowline in Tropical Andes (10º N to 23º S)
  hundreds of meters below todays line during
  coldest phases
• Extended ice caps and glaciers covered summits of
  Colombian, Ecuadorian, Peruvian and Bolivian
  Andes

16
Landforms Origin and Development Glaciation and
Recent Geological History - 2

• Last deglaciation 13,000 11, 000 years ago
• Melting waters filled intermontane lake basins,
  cuencas
• Deposit of lacustrine sediments
• Ecuadorian Andes very fertile soils lacustrine
  sediments overlain by volcanic deposits
• Lake Ballivián N shore of present Titicaca Lake,
  across Poopo Lake into salt flat of Uyuni.
• Shallow, bright salt lakes, salares, in S
  Bolivia, N Argentina and N Chile inhospital
  landscape
• Lake disiccation