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A Look at South American Geology

A Look at South American Geology



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An Overview of South American Geology

Mount Roraima is a 9,220 foot table-top mountain in the Guiana Highlands. This spectacular landform marks the border between Venezuela, Guyana and Brazil. Martin Harvey/Getty Images

For much of its geologic history, South America was part of a supercontinent comprised of many southern hemispheric land masses. South America began to split apart from Africa 130 million years ago and separated from Antarctica within the past 50 million years. At 6.88 million square miles, it is the fourth largest continent on Earth.

South America is dominated by two major landforms. The Andes Mountains, located within the Pacific Ring of Fire, are formed from the subduction of the Nazca plate underneath the entire western edge of the South American plate. Like all other areas within the Ring of Fire, South America is prone to volcanic activity and strong earthquakes. The eastern half of the continent is underlain by several cratons, all over one billion years in age. In between the cratons and Andes are sediment-covered lowlands.

The continent is barely connected to North America through the Isthmus of Panama and is almost completely surrounded by the Pacific, Atlantic and Carribean Oceans. Almost all of South America's great river systems, including the Amazon and Orinoco, begin in the highlands and drain east towards the Atlantic or Caribbean Oceans.

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Generalized Geologic Map of Argentina

Geologic map of Argentina. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Argentina's geology is dominated by the metamorphic and igneous rocks of the Andes to the west and a large sedimentary basin to the east. A small, northeastern section of the country extends into the Río de la Plata craton. To the south, the Patagonia region stretches between the Pacific and Atlantic Oceans and contains some of the largest non-polar glaciers in the world.

It should be noted that Argentina contains some of the world's richest fossil sites that are home to both gigantic dinosaurs and famous paleontologists.

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Generalized Geologic Map of Bolivia

Geologic map of Bolivia. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

The geology of Bolivia is somewhat of a microcosm of South American geology as a whole: Andes to the west, a stable Precambrian craton to the east and sedimentary deposits in between.

Located in southwest Bolivia, Salar de Uyuni is the largest salt flat in the world.

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Generalized Geologic Map of Brazil

Geologic map of Brazil. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Archean-aged, crystalline bedrock makes up a large portion of Brazil. In fact, ancient continental shields are exposed in nearly half of the country. The remaining area is made up of sedimentary basins, drained by large rivers like the Amazon.

Unlike the Andes, the mountains of Brazil are old, stable and have not been affected by a mountain-building event in hundreds of millions of years. Instead, they owe their prominence to millions of years of erosion, which sculpted away the softer rock.

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Generalized Geologic Map of Chile

Geologic map of Chile. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Chile is almost entirely within the Andes range and subranges - around 80% of its land is made up of mountains.

Two of the strongest recorded earthquakes (9.5 and 8.8 magnitude) have occurred in Chile.

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Generalized Geologic Map of Colombia

Geologic map of Colombia. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Much like Bolivia, Colombia's geology is made up of the Andes to the west and crystalline basement rock to the east, with sedimentary deposits in between.

The isolated Sierra Nevada de Santa Marta of northeastern Colombia is the highest coastal mountain range in the world, topping out at nearly 19,000 feet.

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Generalized Geologic Map of Ecuador

Geologic map of Ecuador. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Ecuador rises east from the Pacific to form two imposing Andean cordilleras before descending into the sedimentary deposits of the Amazon rainforest. The famed Galapagos Islands lie approximately 900 miles to the west.

Because the Earth bulges at the equator due to its gravity and rotation, Mount Chimborazo - not Mount Everest - is the farthest point from the center of the Earth.

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Generalized Geologic Map of French Guiana

Geologic map of French Guiana. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

This overseas region of France is almost completely underlain by the crystalline rocks of the Guiana Shield. A small coastal plain extends to the northeast toward the Atlantic.

Most of the ~200,000 inhabitants of French Guiana live along the coast. Its interior rainforest is largely unexplored.

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Generalized Geologic Map of Guyana

Geologic map of Guyana. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Guyana is split into three geologic regions. The coastal plain is made up of recent alluvial sediment, while older Tertiary sedimentary deposits lie south. The Guiana Highlands form the large interior section.

The highest point in Guyana, Mt. Roraima, sits on its border with Brazil and Venezuela.

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Generalized Geologic Map of Paraguay

Geologic map of Paraguay. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Although Paraguay lies at the crossroads of several different cratons, it is mostly covered in younger sedimentary deposits. Precambrian and Paleozoic basement rock outcrops can be seen at the Caapucú and Apa Highs.

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Generalized Geologic Map of Peru

Geologic map of Peru. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

The Peruvian Andes rise sharply from the Pacific Ocean. The coastal capital city of Lima, for instance, goes from sea level to 5,080 feet within its city limits. The sedimentary rocks of the Amazon lie east of the Andes.

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Generalized Geologic Map of Suriname

Geologic map of Suriname. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Much of Suriname's land (63,000 square miles) consists of lush rainforests that sit upon the Guiana Shield. The northern coastal lowlands support most of the country's population.

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Generalized Geologic Map of Trinidad

Geologic map of Trinidad. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Although slightly smaller than Delaware, Trinidad (the main island of Trinidad and Tobago) is home to three mountain chains. Metamorphic rocks make up the Northern Range, which reaches 3,000 feet. The Central and Southern Ranges are sedimentary and much shorter, topping out at 1,000 feet.

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Generalized Geologic Map of Uruguay

Geologic map of Uruguay. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Uruguay sits almost entirely upon the Río de la Plata craton, with much of it covered by sedimentary deposits or volcanic basalts.

Devonian Period sandstones (purple on the map) can be seen in central Uruguay.

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Generalized Geologic Map of Venezuela

Geologic map of Venezuela. Map derived by Andrew Alden from US Geological Survey OFR 97-470D

Venezuela consists of four distinct geologic units. The Andes die out in Venezuela and are bordered by the Maracaibo Basin to the north and the Llanos grasslands to the south. The Guiana Highlands make up the eastern portion of the country.