Primordial Reservoirs Fuel Volcanic Hotspots.

PositionGEOCHEMISTRY

The Earth's mantle--the layer between the crust and the outer core --is home to a primordial soup even older than the moon. Among the main ingredients is helium-3 (He-3), a vestige of the Big Bang and nuclear fusion reactions in stars, and the mantle is its only terrestrial source.

Scientists studying volcanic hot-spots have strong evidence of this, finding high helium-3 relative to helium-4 in some plumes, the upwellings from the Earth's deep mantle. Primordial reservoirs in the deep Earth, sampled by a small number of volcanic hotspots globally, have this ancient He-3/4 signature.

Inspired by a paper that proposed a correlation between such hotspots and the velocity of seismic waves moving through the Earth's interior, Matthew Jackson, geochemist at the University of California, Santa Barbara, teamed with the authors of the original paper--Thorsten Becker of the University of Texas, Austin, and Jasper Konter of the University of Hawaii, Honolulu--to show that only the hottest hotspots with the slowest wave velocity draw from the primitive reservoir formed early in the planefs history.

"We used the seismology of the shallow mantle--the rate at which seismic waves travel through the Earth below its crust--to make inferences about the deeper mantle," says Jackson, assistant professor in the Department of Earth Science. "At 200 km, the shallow mantle has the largest variability of seismic velocities--more than six percent, which is a lot. What's more, that variability, which we hypothesize relates...

To continue reading

Request your trial

VLEX uses login cookies to provide you with a better browsing experience. If you click on 'Accept' or continue browsing this site we consider that you accept our cookie policy. ACCEPT