U.S. researchers said plate tectonics -- the motion, formation and recycling of the Earth's crust -- may not be a continuous process, UPI reported. Paul Silver of the Carnegie Institution of Washington and Mark Behn of the Woods Hole Oceanographic Institution said they've found evidence that the process of subduction has effectively stopped at least once in Earth's past, WHOI said Wednesday in a release. Subduction occurs when two pieces of the Earth's crust collide and one dives beneath the other back into the interior of the planet. "The scientific community has typically assumed that plate tectonics is an active and continuous process, that new crust is constantly being formed while old crust is recycled," Behn said in a statement. "But the evidence suggests that plate tectonics may not be continuous. Plates may move actively at times, then stop or slow down, and then start up again."
