New Theory of Earth's Moving Surface

SAN DIEGO, July 19 (UPI) — Australian and U.S. researchers say they’ve developed a new theory to explain the global motion and speed of Earth’s tectonic plates.

The new theory may offer understanding of the geological evolution of Earth in the past 50 million years, reported Saturday.

Researchers at Australia’s Monash University and the University of California, San Diego say the speed of plate movements is affected by the size of the subduction zones, those areas where one moving plate dives below another, ScienceDaily said.

“The scalings for how subducted plates sink in the earth’s mantle are based on essentially the same fluid dynamics that describe how a penny sinks through a jar of honey,” UCSD geophysicist Dave Stegman says.

“Computer models demonstrate that the subducted portion of a tectonic plate pulls on the portion of the plate that remains on the earth’s surface,” Stegman says. “This pull results in either the motion of the plate, or the motion of the plate boundary, with the size of the subduction zone determining how much of each.”

This discovery explains why the large Australian, Nazca and Pacific plates can move up to four times faster than the smaller African, Eurasian and Juan de Fuca plates, researchers say.

“The plates themselves are controlling the process more than the mantle underneath,” Stegman says. ” It means Earth is really more of a top-down system than the predominantly held view that plate motion is being driven from the bottom up.”

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