September 11, 2008

Study Improves Forecasting Of Vesuvius Eruptions

French geologists reported Wednesday that the pool of magma feeding the Italian volcano that wiped out Pompeii in 79 AD has shifted during the past two millennia.

The discovery could help with predictions of future eruptions, the researchers said.

Vesuvius is located in southern Italy near Naples, the country's third largest city and one of the world's most densely populated volcanic areas.  Its crater is 4,200 feet above and 13 miles away from the city. 

Scientists had previously believed the pool was steady over the past 4,000 years. However, the new research revealed the chamber had actually shifted higher between the Pompeii eruption and the Pollena one that occurred in 472 AD.

Knowing the precise location of the lava pool is critical because pressure accumulates according to the depth of the pool, resulting in even more powerful eruptions, said Michel Pichavant, who worked on the study.

By accounting for the movement of these pools, more precise models to predict damage from future eruptions can be formulated, said Pichavant, a geologist at the University of Orleans in France.

"We found that there was a substantial variation of the reservoir that is the source of a mass of lava," he said during a Reuters interview.

"These variations need to be documented if we want to make reliable forecasts of future eruptions."

Although Vesuvius has been quiet for the past 60 years, scientists worry the next big eruption could be as large as the one in 79 AD, which killed about 16,000 people and destroyed the ancient cities of Pompeii and Herculaneum.

A 2007 Italian study estimated that 300,000 people living in proximity to the volcano would be killed in a future eruption if they were not evacuated.

In the current study, Pichavant and his team collected rock samples from four major eruptions, and then conducted lab experiments at high pressures and temperatures to simulate the lava as it crystallized where it was originally deposited.

They discovered the reservoirs feeding the eruptions migrated from about 5 miles within the earth's crust during the Pompeii eruption in 79 AD to about 2.5 miles during the Pollena eruption in 472 AD.

Pichavant said that existing technology does not allow scientists to locate the pools until after an eruption, something that makes accurate forecasting so critical.

The research was published in the journal Nature.

Image Courtesy Wikipedia


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