Erupting Vesuvius kills 300,000 -- in simulation

By Phil Stewart

ROME, Feb 27 (Reuters) - At least 300,000 Italians living near the Vesuvius volcano would be killed the next time it erupted if they were not evacuated beforehand, according to the first 3-dimensional super-computer simulation.

But, in a surprise, up to 200,000 others living in the north-northwestern areas of the high-risk "Red Zone" could have more time to escape thanks to the volcano's towering Mount Somma rim, which acts as a natural barrier, scientists say.

"For the first time, we have seen that these flows could be substantially diverted," Augusto Neri, of the National Geophysical and Vulcanolgy Institute in Pisa, who led the research, said on Tuesday.

"It seems that Mount Somma acts as an effective barrier. But this doesn't mean that they're safe."

Although Vesuvius has slept for more than six decades, scientists fear the next big eruption could rival the one in AD 79, which suffocated the ancient cities of Pompeii and Herculaneum and killed about 16,000 people.

Authorities have a plan to evacuate the more than half a million civilians living in the 18 towns within a 7 km (about 4 mile) radius of Vesuvius who face the highest risk. They estimate they can get everyone to safety within a week.

Neri's research, published in Geophysical Research Letters, could give authorities a greater understanding of how the volcano will behave in the event of a big eruption -- and which of those 18 communities need to be evacuated first. "We've already passed the civil protection authorities these results. They are going to consider some of the results of this simulation in the revision of their emergency plan," he said.



POMPEII AGAIN?

Peter Baxter, at Cambridge University's Institute of Public Health, who also participated in the study, said history looked set to repeat itself by pummelling modern-day communities around the ruins of Pompeii and Herculaneum.

"The pyroclastic flows are going to be pushed to the south-side, toward the sea," he said, adding "that's where Pompeii and Herculaneum are".

Neri said the Vesuvius computer simulation was the first in 3-D that showed what a big eruption would look like over a period time, factoring in complex variables such as topography.

The scientists specifically tried to simulate the effects of a collapse of the eruption column -- what happens when the exploding mushroom cloud is too heavy for the air, and the material comes crashing down the sides of the volcano.

The crater sits some 1,280 metres (4,200 feet) above and 20 km (13 miles) away from the Naples, Italy's third largest city.

The simulation calculated the temperature of magma would be 950 degrees Celsius (1,742 degrees Fahrenheit) as it left the crater and 200 C at the outer edge of the Red Zone, 7 km away.

Carlo Cavazzoni, who helped developed the code that allowed the super-computer to interpret the data, said the team partly based its research on an eruption in 1631 that killed 4,000 people.

Neri said many more simulations were needed but said the first 3-D model was a major step forward.

"It's the first time that such a complete model has been applied at Vesuvius," he said.