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No. 103: Jan-Feb 1996

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Fossil Mantle Plume Under South America

"In a challenge to a major aspect of the theory of plate tectonics, NSF-supported scientists have discovered the presence of an ancient conduit deep in the Earth's mantle beneath Brazil.

"The conduit appears to have remained geographically fixed with respect to the overlying continent despite thousands of kilometers of South American plate motion. This observation runs contrary to a major tenet of plate tectonic theory -- that the motion of lithospheric plates is essentially independent of flow in the upper mantle beneath the plates -- and implies that the upper mantle and the overlying South American continent have remained coupled since the breakup of the Gondwanaland super-continent and opening of the South Atlantic Ocean some 120 million years ago. This result also implies that large-scale convection in the mantle may be responsible for the motion of the great continental plates, such as South America, where the driving force for plate motion has not been well understood."

(Dybas, Cheryl; NSFNEWS Digest 54, November 8, 1995. Cr. D. Swaner. NSF= National Science Foundation. The cyber-address for the NSFNEWS Digest is: nsfnews@nsf.gov

The computerless may read more in: VanDecar, John C., et al; "Seismic Evidence for a Fossil Mantle Plume beneath South America and Implications for Plate Driving Forces," Nature, 378:25, 1995.

From Science Frontiers #103, JAN-FEB 1996. 1996-2000 William R. Corliss