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Volcanic Super-Eruptions A Quicker Threat Than Previously Thought

May 31, 2012
Image Caption: Two layers of the Bishop Tuff: lower layer was from ashfall, upper layer was from the main pyroclastic flow. Credit: Roy A. Bailey/USGS

Lee Rannals for RedOrbit.com

Volcanoes capable of super-eruptions that could be catastrophic for civilizations have short fuses, according to new research conducted at Vanderbilt University.

Super-eruptions are more than 100 times the size of ordinary volcanic eruptions like Mount St. Helens. These types of eruptions spew out super-heated gas, ash and rock, and are capable of leveling entire continents.

Researchers say that there is evidence of one super-eruption that took place in Indonesia 74,000 years ago that came close to wiping out the entire human species.

Geologists believe that a super-eruption is produced by a giant pool of magma that forms a couple of miles below the surface of the Earth, simmering for 100,000 to 200,000 years before erupting. However, a new study says the time frame that these giant magma pools can form and erupt may be shorter than previously thought.

According to the latest study published in the journal PLoS ONE, these giant volcanoes may only exist for a few thousand years before erupting.

“Our study suggests that when these exceptionally large magma pools form they are ephemeral and cannot exist very long without erupting,” Guilherme Gualda, the assistant professor of earth and environmental sciences at Vanderbilt University, said.

The researchers investigated remnants of the Bishop Tuff for their study, which is the Long Valley super-eruption that occurred in east-central California 760,000 years ago.

The team used the latest methods for dating the process of magma formation and found several independent lines of evidence that indicate the magma pool formed within a few thousand years, potentially even within a few hundred years, before erupting.

These giant magma pools are shaped like pancakes and are 10 to 25 miles in diameter, and one half to three miles deep.

During the beginning of developing a super eruption, molten rock in these pools is mostly free from crystals and bubbles, but once they form, these elements that help make up the eruption form gradually and progressively, changing the magma’s physical and chemical properties.

Geologists do not know of any giant crystal-poor magma body that currently exists, but the team believes this magma body only exists for a short period of time, as opposed to previous theories of lasting for thousands of years.

The researchers determined crystallization rates of quartz in order to obtain information about the lifespan of the giant magma bodies.

They developed four independent lines of evidence that agreed that the formation process took less than 10,000 years, and most likely between 500 to 3,000 years, before the eruption.

Gualda and his colleagues suggest that the zircon crystal measurements record the extensive changes that took place in the crust that was required before the giant magma bodies start forming.

“The fact that the process of magma body formation occurs in historical time, instead of geological time, completely changes the nature of the problem,” Gualda wrote.

He said that geologists need to regularly monitor areas where super-eruptions are likely to occur, which would help provide advanced warning if a magma body begins to form.

Image 2 (below): 3-D view of Long Valley, Calif., created by imaging radar on the space shuttle Endeavor. (NASA/JPL)


Source: Lee Rannals for RedOrbit.com

Volcanic Super-Eruptions A Quicker Threat Than Previously


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