Given the general understanding now that the earth’s crust is divided into “continental plates,” and that these plates move, rubbing against one another in such a way as to produce earthquakes and volcanic activity: what is the cause of the movement (the “continental drift”) itself? The usual hypothesis is that the plates move in response to convention currents in the mantle, beneath them. But there is now an alternative view.
Anne M. Hofmeister, a geophysicist at Washington University in St. Louis, and two other scientists working with her, recently published their take on the question of the driving force behind the drift in a special paper of the Geological Society of America, as part of a forthcoming collection assembled in honor of geologist Warren B. Hamilton.
Strange New Worlds:
The earth’s plates might be shifting because the sun exerts a strong gravitational pull on the earth’s moon that over time has caused the moon’s orbit around Earth to become elongated. This is turn has shifted the oscillating center of the Earth-moon system, leading to a variety of plate motions on Earth. In brief, then: the driving force comes from above, not from below.