This map of topography and water depth along the Chilean coast shows quake locations and magnitudes (black circles), with lighter colors indicating higher elevation on land and shallower depth in the water. The boundary where the two tectonic plates converge is marked by a red line. Also there is a trench where the Nazca Plate begins to dive beneath the South America Plate. When these plates get locked together for any time the pressure will eventually break, resulting in an earthquake like the 8.8 magnitude temblor on Feb. 27. Credit: NASA Earth Observatory.
From Live Science:
The 8.8-magnitude earthquake that devastated parts of Chile was the result of a collision between two giant slabs of Earth.
The jolt occurred along a so-called subduction zone, where one tectonic plate dives beneath another. In this case, the Nazca Plate is plowing under the South America Plate at an average rate of 3 inches (80 millimeters) a year. In addition to the Feb. 27 earthquake and others, the plate collision gives rise to the spectacular Andes Mountains.
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