South American Plate
My Blogs (olelog) are mainly based on my daily reading of earth science news.
Here on whatonearth.olehnielsen.dk I try to weave some of the pieces together to a greater whole with added background info.
The South American Plate is a tectonic plate covering the continent of South America and extending eastward to the Mid-Atlantic Ridge.
The easterly side is a divergent boundary with the African Plate forming the southern part of the Mid-Atlantic Ridge. The southerly side is a complex boundary with the Antarctic Plate and the Scotia Plate. The westerly side is a convergent boundary with the subducting Nazca Plate. The northerly side is a boundary with the Caribbean Plate.
The remains of the Farallon Plate, split into the
current Cocos Plate and Nazca Plate are still subducting
under the western edge of the South American Plate. This subduction is responsible
for lifting the massive Andes Mountains and causing the volcanos
which are strewn throughout them. There is some speculation that in addition
to subducting the Cocos and Nazca Plates, the westward motion of the South American
Plate may have forced the Caribbean and Scotia Plates at its northern and southern
ends respectively to squeeze around it. Both share a similar shape and are being
subducted along their eastern boundary. They are thought to be ancient volcanic
regions formed on the Farallon Plate, with their crust too thick to be subducted
under the South American Plate.
The Andes has three volcanic zones marked A, B and C on the map to the right. Active volcanic centres correlate with regions where the dip of the subduction zone is about 30°. Where the dip is shallow, 5-10°, there are no active volcanoes. Peru (green on map) is known for having a flat subduction.
The peaks of the central Andes stand at an average height of 4 kilometres. Previous calculations based on models of plate tectonics have at times suggested they ought to be half that height. Different theories have been advanced for why the Andes are unusually high. According to a letter in Nature of 15 march 2007 it could all be down to the extremely long length of the subduction zone along the west coast of the South American continent.
Plate boundaries in Southern South Americas based on USGS map.
Purple line = Subduction zone
Red Line = Spreading Ridge
Green Line = Transform Fault
a volcano in Ecuador
Why are the Andes so High?
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