In today's news:
WASHINGTON (AP) - Two superplumes of molten rock appear to be powering through the boundary between the Earth's upper and lower mantle, perhaps feeding volcanoes and affecting movement of the planet's crust.
New evidence of the superplumes - located beneath the south central Pacific Ocean and southern Africa - comes from studies of seismic waves conducted by scientists at the University of California at Berkeley and reported in Friday's issue of the journal Science.
Smaller regions of magma rising to the Earth's crust power volcanoes and other hot spots.
But the superplumes come from far deeper, crossing the boundary between the upper and lower mantle about 400 miles deep, an area that had been thought by some scientists to impede the flow of material.
Researcher Barbara Romanowicz said earthquake studies until now have emphasized the dynamics of collisions between the planet's massive surface plates. When two of them crash together, one slips beneath the other in a process called subduction, and earthquakes and volcanoes can follow. "We think the superplumes play an important role as well," Romanowicz said.
The study seeks to focus attention on the hot material rising upward from the base of the mantle - the partially molten region that extends about 1,740 miles from the Earth's core to its crust, or lithosphere.
"The hot material brought under the lithosphere by the superplumes then spreads out horizontally toward mid-ocean ridges," Romanowicz explained. The ridges are often active volcanic areas.
