New York, Sep 8:
Seismologists from University of California-Berkeley have produced for the first time a sharp, three-dimensional scan of Earth’s interior that shows how volcanic island chains like Hawaii, Samoa and Iceland were born.
The results conclusively connect plumes of hot rock rising through the Earth’s mantle with surface hotspots that generate volcanic island chains, the study said.
While medical computed tomography, or CT scans employ X-rays to probe the body, the scientists mapped mantle plumes by analysing the paths of seismic waves bouncing around Earth’s interior after 273 strong earthquakes that shook the globe over the past 20 years.
Previous attempts to image mantle plumes have detected pockets of hot rock rising in areas where plumes have been proposed, but it was unclear whether they were connected to volcanic hotspots at the surface or the roots of the plumes at the core mantle boundary 2,900 kilometers below the surface.
The new, high-resolution map of the mantle — the hot rock below Earth’s crust but above the planet’s iron core — not only shows these connections for many hotspots on the planet, but reveals that below about 1,000 kilometers the plumes are between 600 and 1,000 kilometers across, up to five times wider than geophysicists thought.
The plumes are likely at least 400 degrees Celsius hotter than surrounding rock.
“No one has seen before these stark columnar objects that are contiguous all the way from the bottom of the mantle to the upper part of the mantle,” said first author Scott French, a computational scientist at US Department of Energy’s National Energy Research Scientific Computing Centre (NERSC).
The findings were detailed in the journal Nature. (IANS)