Scientists offer new
theory on isles
deep lava source
The study asserts that hotspots
are actually drifting, not stationary
By Mary Vorsino
Nature's dispensers of magma from the Earth's mantle -- called hotspots -- have long been thought stationary.
But a team of researchers studying the hotspot that created the Hawaiian Islands has released a theory that the formations drift, just like tectonic plates.
If the findings published in the journal Science late last month can withstand the criticism mounting against them, they could shatter long-standing knowledge about how "things work in the innards of the Earth," said David Scholl, a consulting professor with Stanford University and a scientist emeritus with the U.S. Geological Survey in Menlo Park, Calif.
That means everything from how plates move to how land masses are formed may have to be rethought.
"We blew the doors of the car off and opened up all sorts of major league questions," Scholl said in an interview.
Until now, researchers have theorized that the massive Pacific plate -- which stretches across most of the northeast Pacific Ocean basin -- has been slowly moving over a fixed Hawaiian hotspot, leaving a trail of volcanoes whose peaks emerge from the ocean as islands.
This segment, known as the Hawaiian Ridge, forms a nearly straight line of seafloor mountains that extends 1,800 miles northwest across the Pacific.
But when the Hawaiian Ridge meets the Emperor Seamounts -- an older volcanic chain -- the direction of the formations abruptly change course, stretching more than 1,000 miles almost due north to Alaska's Aleutian Trench.
Scientists have long attributed that change, or bend, to a plate shift.
But Scholl and his colleagues say it was the hotspot -- not the plate -- that made the turn southward between 47 million and 81 million years ago at a rate of about two inches per year.
There are about 40 known hotspots in the world and they litter the Pacific, Atlantic and Indian oceans and elsewhere.
If it proves correct, the study could put into question whether major plates can undergo large changes in direction without the help of other geological phenomena, like hotspots, Scholl said.
But some scientists are still hesitant to throw decades of plate and hotspot research away.
Paul Wessel, a professor of geology and geophysics at the University of Hawaii, is skeptical of the findings, saying he doesn't think the data fit the conclusion.
"I don't think this is a viable explanation," he said in an interview.
Wessel said he has prepared an article for submission to the journal Nature that rebuts Scholl's argument, titled "The Hawaii Emperor Bend: An Unequivocal Record of Pacific Plate Motion Change."
The paper's co-author, fellow geophysicist Loren Kronenky, said, "We've got eight hotspot trails across the Pacific (Plate). They're all going to have to be moving together" if Scholl's conclusion is correct.
Scholl's team bases its study on differing magnetic directions of the magnetite, or lava induced with magnetic residues that align with the Earth's magnetic poles, in the Hawaiian Ridge and Emperor Seamounts.
If the hotspot had been fixed, samples of magnetite in both areas would have given identical magnetic readings, Scholl said. But they did not, he said.