What causes lava to spurt from volcanoes in plumes of liquid fire or cause the ground to shake as if the world were ending? Tectonic plates. What causes plate tectonics? Not so fast.
Until now, the answer was thought to be unrest in the Earth’s mantle. Under intense heat and pressure, superheated magma rises in what is called convection currents, pushing tectonic plates from the crust on it. The problem is that even some hardcore proponents of the convection current hypothesis doubt that the influence of convection currents is strong enough to cause literal earthquake phenomena. So what?
Gravity maybe that’s it. Geophysicist Anne Hofmeister of Washington University in St. Louis, who led a study recently published in Journal of the Geological Society of America, proposes that the gravitational attraction between the Earth, the Sun and the Moon can cause imbalances that lead to the displacement of tectonic plates. The Sun pulls on the Moon with such force that it creates an elongated lunar orbit that causes all sorts of problems for fragile terrestrial planets. lithosphere.
“Available data does not support the convection model,” Hofmeister told SYFY WIRE. “Among other things, the heat source is insufficient, rocks require tremendous forces to deform, thermal plumes do not exist, and convection only affects fluids, not solids.”
The way the Moon’s orbit is accelerating is at odds with the way the Sun – a body tens of millions of times more massive – pulls on it. Lunar orbital acceleration and solar attraction are thought to balance each other at centroid between the Earth and the Moon. The center of mass is the center of mass between them. Although it’s usually just between similar-sized objects, Earth’s greater mass means the Earth-Moon barycenter is closer to us (it’s been getting closer for billions of years). About 2,860 miles from our planet’s core, it’s not directly between us and the Moon.
The barycenter is the only place where the acceleration of the Moon’s orbit and the persistent attraction of the Sun balance each other. Unfortunately, it’s in space. Everywhere else, these forces are out of balance, and the Earth’s crust and solid upper mantle, which together form the lithosphere, cannot support it. Tectonic plates become unstable and break. They slide, crash and subduct, often with catastrophic results on the surface. from flame-spewing volcanoes to earthquakes, which are dangerous enough but often also cause mudslides and tsunamis.
“The geocenter oscillates around the orbital plane of the barycenter, so the directions of the forces are not aligned,” Hofmeister said. “The rotation of the Earth is also important for the movements of the plates, giving the east-west character, which has been shown with the seismic data. Convection can’t do that.
Pluto could actually be a mirror of what’s happening on Earth. Because it is too small for stirring convection currents to bubble up inside, this is ruled out, but it does have plate tectonics. The retrograde planet’s moon is also large relative to its size, much like Earth’s, and its surface isn’t as old as most objects in the Kuiper Belt, which lies beyond. To further test his hypothesis, Hofmeister wants to analyze its orbital dynamics and time dependence to see how they compare to those of the Earth, Sun, and Moon.
“Heat-emitting elements are mostly found in the Earth’s crust, so how the mantle might be heated is a long-standing question,” she said. “Fifty years of convective modeling failed to explain any of our observations.”