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Scientists answer ring of fire's riddle |
| TheAllINeed.com |
(NC&T/MU) The team of researchers, based at Monash University and ANU, investigated what happens when one tectonic plate sinks underneath another and found that the boundaries between tectonic plates move just as fast as the plates themselves. The new theory, published today in Nature, explains how plate boundaries evolve over millions of years to produce the arc-shaped segments found all around the world.
Geophysicist, Dr Dave Stegman of Monash University, said experts have never really known why only a few sections of the Ring of Fire are curved in the same direction as the ring itself while most sections are curved in the opposite direction. According to the team's findings, the length of the boundary between tectonic plates, places where great earthquakes occur, controls whether it curves one way or the other. Many of these boundaries on Earth, including most of those, which comprise the Ring of Fire, are less than 3000 km long, which tend to curve into a concave shape.
Dr Stegman said the team worked several years to develop the ideas and computer models used in the study. The group of researchers, including Assoc Professor Louis Moresi and David May, a PhD student at Monash University, and scientists Dr. Wouter Schellart and Dr. Justin Freeman from ANU, also enlisted the help of the largest supercomputer in Australia to simulate the detailed processes deep inside the Earth.
"The key to understanding subduction is that every tectonic plate that gets recycled into the Earth's interior has a finite extent corresponding to length of the plate boundary on the surface. It is an inherently three-dimensional process because once the plate has entered the mantle, the surrounding material can flow around its edges," explained Dr Stegman. The computer models allowed the team to understand exactly how the Earth's interior interacts with recycled plates.
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"We found that as the subducted plate sinks into the Earth's deep interior, it curls up because it is deformed as the mantle flows around its edge. This curling is expressed on the surface as the curvature of the subduction zone - producing an arc-shaped boundary which generally migrates backwards relative the motion of the tectonic plate," Dr Stegman said.
Potentially the biggest implication of the research is for the Andes mountains in South America, the longest and second highest mountain chain in the world, situated above the longest subduction zone on Earth.
Usually, mountain ranges are created by the collision of continents, but these mountains occur where an oceanic plate is sinking below a continental plate. However, because the plate subducting underneath South American is so wide, its interaction with the mantle below is quite different. The result is the Andes mountains -- rising up around the subducted plate's centre near Bolivia where it is very far from the plate's edges.
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