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Another Krakatoa, East of Java? World's largest volcano found beneath Pacific Ocean

By Catholic Online (NEWS CONSORTIUM)
September 6th, 2013
Catholic Online (www.catholic.org)

Researchers say that the world's largest volcano lurks beneath the Pacific Ocean. Called the Tamu Massif, the new discovery dwarfs Hawaii's Mauna Loa, the previous record holder. Tamu Massif is only 25 percent smaller than Olympus Mons on Mars, the biggest volcano in Earth's solar system.

LOS ANGELES, CA (Catholic Online) - "We think this is a class of volcano that hasn't been recognized before," William Sager, lead study author and a geologist at the University of Houston says. "The slopes are very shallow. If you were standing on this thing, you would have a difficult time telling which way was downhill."

Tamu is 400 miles wide but only about 2.5 miles tall, erupting for a few million years during the early Cretaceous period, about 144 million years ago. It has since been extinct.

Tamu Massif seems to have a central cone that spewed lava down its broad, gentle slopes. Seismic surveys and lava samples collected over several years of surveys by research ships suggest this. Seismic waves show lava flows dipping away from the summit of the volcano. There appears to be a series of calderas at the summit, similar in shape to the elongated and merged craters atop Mauna Loa, Sager says.

Geologists previously thought Tamu Massif was simply part of an oceanic plateau called Shatsky Rise in the northwest Pacific Ocean. These plateaus are massive piles of lava whose origins are still a matter of active scientific debate.

Some researchers think plumes of magma from deep in the mantle punch through the crust, flooding the surface with lava. Others plateaus suggest pre-existing weaknesses in the crust, such as tectonic-plate boundaries, provide passageways for magma from the mantle, the layer beneath the crust.

With its new status as a single volcano, Tamu Massif could help constrain models of how oceanic plateaus form. "For anyone who wants to explain oceanic plateaus, we have new constraints," sager says. "They have to be able to explain this volcano forming in one spot and deliver this kind of magma supply in a short time."

Geochemist David Peate of the University of Iowa says he looks forward to new models explaining the pulses of magma that built Shatsky Rise. Tamu Massif is the biggest and oldest volcano, and the cones grow smaller and younger to the northeast of Tamu. Sager and his colleagues suggest that pulses of magma created the volcanic trail.

"It seems that in many oceanic plateaus the melting is continuous, but here you have a big shield volcano," Peate, who was not involved in the study says. "Understanding the source of the volume of that magma, the rate of production of the magma and the time interval between those pulses will help give better constraints to feed into those models," he said.

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