(ORDO NEWS) — A new study by a team led by geophysicist Anne M. Hofmeister at Washington University in St. Louis, USA, suggests that unbalanced forces and moments in the Earth-Moon-Sun system are driving the circulation of the mantle as a whole.
This new analysis offers an alternative to the hypothesis that the movement of tectonic plates is due to convection currents in the Earth’s mantle.
Convection is the buoyancy of heated liquids, and the concept doesn’t apply to solid rocks, Hofmeister and her colleagues say. In their opinion, the movements of large objects are caused by mechanical forces, and not by heat.
Processes in the interior of the Earth are often modeled as the dissipation of heat generated by internal radioactivity and residual energy from cosmic collisions that occurred during the formation of the planet.
But even supporters of the hypothesis of convection mixing of mantle material admit that the amount of internal thermal energy is insufficient for large-scale plate tectonics. There are also other problems associated with the use of convection to explain the observed movements of the lithospheric plates.
Instead, the movement of the lithospheric plates may be due to the fact that the Sun has such a powerful gravitational effect on the Moon that it causes the Moon’s orbit to stretch around the Earth.
Over time, the position of the barycenter – the center of mass between two bodies moving in a common orbit, the Earth and the Moon – has shifted closer to the Earth’s surface and is currently oscillating, shifting 600 kilometers each month relative to the center of the Earth, Hofmeister explained.
As a result, internal stresses arise as the Earth continues to rotate on its axis.
“Because the oscillating barycenter lies about 4,600 kilometers from the center of the Earth, the Earth’s tangential orbital acceleration and the Sun’s gravitational pull are unbalanced nowhere but the barycenter itself,” Hofmeister said. “The planet’s warm, thick, and strong inner layers can withstand these stresses, but its thin, cold, and brittle lithosphere is cracking.”
But how to test this hypothesis? Hofmeister says one possible test would be a detailed study of plate tectonics on Pluto, which is too small and too cold for convection but enters a system with a massive satellite and has a surprisingly young surface.”
The study is published in a special collection of papers of the American Geological Society dedicated to geologist Warren B. Hamilton.
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