The researchers compiled data from thousands of earthquakes recorded at more than a thousand stations to create a detailed 3-D map of the core-mantle boundary.
Using this map, the team then estimated the temperature based on two key factors: pressure and mineral content.
For instance, scientists already knew the temperature at which a mineral in the mantle called pervoskite transforms into a high-pressure material called post-pervoskite.
The transition takes place in the lowermost mantle, just above the core, the new data suggested. This in turn provided a correlating temperature for the core-mantle boundary.
Such findings could shed light on how heat flows from Earth's core into the mantle, said Donald Helmberger, a professor of geological and planetary sciences at the California Institute of Technology.
This heat flow drives the planet's magnetic field and is still poorly understood (related: "North Magnetic Pole Is Shifting Rapidly Toward Russia" [December 15, 2005]).
"Every technique we can bring to bear to study these things is a step forward," Helmberger said.
Edward Garnero is a professor of geological sciences at Arizona State University who also uses seismology to study the deep interior.
This kind of research could demystify how the planet evolved, he said (related: early-Earth interactive).
Knowing Earth's temperature at such depths can tell scientists how much the core has cooled over time and how fast it is cooling now.
"We live on this amazing planet, and we still don't know for certain the processes that go on inside it," Garnero said.
"This paper represents another little piece that brings it into a sharper focus."
Free Email News Updates
Best Online Newsletter, 2006 Codie Awards
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
|
SOURCES AND RELATED WEB SITES
|
