Geology of Chile
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The geology of Chile is heavily influenced by the rise of the Andes mountains and the subduction zone at at its coast. Three mayor morphological features are present in most of the country; the Andes Mountains, the Chilean Coast Range and the Chilean Central Valley (also called intermediate depression) between them. These features run parallelly in a north-south direction from Morro de Arica to Taitao Peninsula, covering up most of Chile's land surface. Further south from Taitao only the Andes Mountains is present. Four mayor tectonic plates are present within or close to Chile's borders, the Antarctic Plate, the Nazca Plate, the Scotia Plate and the South American Plate. Other minor geological areas of Chile include the Altiplano near Bolivia, parts of the Patagonian shield, Juan Fernández Islands and Easter Island.
The Andes Mountains tend to lose height to the south of Chile. As Chile borders the ring of fire, it host a large number of volcanoes, some of them very active like Villarrica and Mount Hudson. The Great Chilean Earthquake or Valdivian Earthquake (Terremoto de Valdivia in Spanish) of 22 May 1960 is the most powerful earthquake ever recorded, rating 9.5 [1] on the Moment magnitude scale.
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[edit] Geologic history
[edit] Mesozoic
Some 250 million years ago during the Triassic period, Chile was part of the supercontinent Pangea which concentrated all major land masses in the world. In Pangea Africa, Antarctica, Australia and India were closest to Chile. When Pangea began to split apart in the Jurassic, South America and the the adjacent land masses formed Gondwana. Floral affinities among these now-distant landmasses date from the Gondwanaland period (see also: Antarctic Floristic Kingdom). Then India split apart followed by the creation of the Mid-Atlantic Ridge that separates Africa from South America.
The formation of the Andes began in the Jurassic Period. It was during the Cretaceous Period that the Andes began to take their present form, by the uplifting, faulting and folding of sedimentary and metamorphic rocks of the ancient cratons to the east. 27 million years ago South America separated from Antarctica and Australia with the genesis of the Drake Passage. Tectonic forces along the subduction zone along the entire west coast of South America where the Nazca Plate and a part of the Antarctic Plate are sliding beneath the South American Plate continue to produce an ongoing orogenic event resulting in minor to major earthquakes and volcanic eruptions to this day. In the extreme south a major transform fault separates Tierra del Fuego from the small Scotia Plate. Across the 1,000 km (620 mi) wide Drake Passage lie the mountains of the Antarctic Peninsula south of the Scotia Plate which appear to be a continuation of the Andes chain.
[edit] Cenozoic
The Pleistocen glaciations have left visible marks in most of Chile but particulary in Zona Sur and Zona Austral. These incluides ice fields, fjords, glacial lakes and u-shaped valleys. At 42° S cuaternary glaciers penetrated into the Pacific Ocean dividing the Chilean Coast Range and created what is now Chacao Channel. Chiloé that used to be a continuous part of the Chilean Coast Range became an island after the creation of Chacao Channel. South of Chacao Channel Chile's coast is split by fjords, islands and channels. The last remains of the Patagonian Ice Sheet that once covered up large parts of Chile and Argentina are the Northern Patagonian Ice Field and the Southern Patagonian Ice Field. The coast in south-central Chile have had a generalized cuaternary rise despite of the holocene transsgressions.[1]
[edit] Pacific Islands
Easter Island is a volcanic high island, consisting of three extinct volcanoes: Terevaka (altitude 507 metres) forms the bulk of the island. Two other volcanoes, Poike and Rano Kau, form the eastern and southern headlands and give the island its approximately triangular shape. There are numerous lesser cones and other volcanic features, including the crater Rano Raraku, the cinder cone Puna Pau and many volcanic caves including lava tubes.
Easter Island and surrounding islets such as Motu Nui, Motu Iti are the summit of a large volcanic mountain which rises over two thousand metres from the sea bed. It is part of the Sala y Gómez Ridge, a (mostly submarine) mountain range with dozens of seamounts starting with Pukao and then Moai, two seamounts to the west of Easter Island, and extending 2,700 km (1,700 mi) east to the Nazca Seamount.
Pukao, Moai and Easter Island were formed in the last 750,000 years, with the most recent eruption a little over a hundred thousand years ago. They are the youngest mountains of the Sala y Gómez Ridge, which has been formed by the Nazca Plate floating over the Easter hotspot.[2] Only at Easter Island, its surrounding islets and Sala y Gómez does the Sala y Gómez Ridge form dry land.
[edit] Mineral resources
Chile has the world's largest copper reserves and is also the largest producer and exporter of the mineral.[3] Some well-known copper mines are Chuquicamata and Escondida. Chile stands for 5% of the western hemispheres gold production of witch 41% is biproduct of copper extraction.[3] Apart from copper Chile contain the largest share of the world reserves of rhenium[3] and potassium nitrate. Chile's reserves of molybdenum are estimated to be the third largest in the world.[3] While most of Chile's mineral resources are in the north there is some minor gas and oil reserves in the southern Magallanes Region, but is otherwise highly dependent of fuel imports.
Guarello Island in Magallanes Region has currently the world's southernmost limestone mine.
[edit] See also
[edit] References
- ^ U.S. Geological Survey (March 7, 2006). Historic Earthquakes - Chile - 1960 May 22 19:11:14 UTC - Magnitude 9.5: The Largest Earthquake in the World. Retrieved on 2007-01-09
- ^ The Petrogenetic Evolution of Lavas from Easter Island and Neighbouring Seamounts, Near-ridge Hotspot Volcanoes in theSE Pacific
- ^ a b c d U.S. Geological Survey (2005). Minerals Yearbook 2005.
[edit] External links
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