Scientists have long known that the Earth's crust consists of at least 15 tectonic plates--continent-sized slabs of rock on the surface of the Earth that shift about to create mountains, volcanoes, and earthquake zones. But the exact mechanism by which the plates move has remained a mystery.
Until now.
A new study suggests that the plates glide about on a six-mile-thick hidden channel of "soft" rock located between the base of the plates and the upper portion of the Earth's mantle (the layer of molten rock above the planet's core), Live Science reported.
“The idea that Earth’s surface consists of a mosaic of moving plates is a well-established scientific paradigm, but it had never been clear about what actually moves the plates around," study co-author Dr. Tim Stern, a professor of geography, environment and earth sciences at Victoria University of Wellington in New Zealand, said in a written statement. “To work this out requires an understanding of what happens at the bottom of a tectonic plate."
The data showed that the seismic waves slowed abruptly at the base of the plate--which suggests that they must have hit a hidden layer of jelly-like rock, Cosmos magazine reported.
The researchers hypothesize that the soft rock creates a slippery base upon whichplates drift when they are pushed or pulled--though exactly what is doing the pushing or pulling is still up for debate.
