[SunkenCiv]

Fossil Mantle Plume Under South America
by William R. Corliss
Science Frontiers #103
Jan - Feb 1996

"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

[SunkenCiv]

Debate Stirs On Hotspot Volcanoes
by Randolph E. Schmid

The most common theory in recent years has been that hotspots exist in the Earth where molten lava wells up from deep below, creating volcanoes such as those that formed Hawaii and Iceland and seismic zones such as Yellowstone. But Gillian Foulger of the University of Durham, England, and James Natland of the University of Miami point out in the journal Science that efforts to find evidence of hotspots using seismic waves have not produced results... In a separate paper in the same journal, Donald J. DePaolo and Michael Manga of the University of California, Berkeley, agree that so far seismological studies searching for hotspots have not produced the expected proof. But they say they expect the evidence to be found. Theoretical and laboratory studies predict deep hot plumes, they note, and there is supporting evidence in the Hawaiian Island chain, with the rising lava building a line of islands as the overriding crust moves along, evidence of a stationary hotspot deep in the earth.