Four thousand years before the eruption of Mt. Vesuvius that wiped out Pompeii, a much more devastating eruption occurred, according to vulcanologists, who say the disaster caused the social and economic collapse of the surrounding area for centuries. Researchers say the event suggests that Vesuvius could some day wreak havoc on a more massive scale.

Scientists know of about eight eruptions of southern Italy's Mt. Vesuvius that have occurred in its 25,000-year history.

The Pompeii eruption of 79 A.D that unleashed a wall of ash that froze the residents in their tracks, is the best known.

Now, vulcanologists reporting in Proceedings of the National Academy of Sciences, say a much more devastating eruption of Vesuvius occurred almost 4,000 years before Pompeii.

After the cataclysmic surges of lava finally subsided, the Avellino eruption blew what geologist Michael Sheridan and colleagues say was extremely hot ash to the edges of Naples some 25 kilometers away.

Sheridan, who teaches at the University of Buffalo, says the discovery contradicts the belief by most scientists that Naples is safe from Vesuvius.

"I think this is really a major finding, finding up to three meters of ash that was traveling along the ground at hurricane velocities like the blast at Mount St. Helens," said Michael Sheridan. "It would be like the blast of Mount St. Helens occurring but having a city that was destroyed."

The St. Helens volcano, located in the northwestern state of Washington, erupted for nine hours straight in 1980 and claimed 57 lives.

Like Pompeii, Sheridan, who studies volcanic hazards at the University of Buffalo in New York, says Avellino froze communities just the way they were at the time of the eruption.

Most striking are the homes that are perfectly preserved by the volcanic fallout, including eating utensils and food in bowls.

"And then the footprints," he said. "Thousands of footprints."

While many people died of asphyxiation of hot gases, vulcanologist Michael Sheridan says most got away in time to save their lives.

"People as soon as they saw this drastic thing happening, they didn't grab anything," explained Sheridan. "They just took off out of there."

During the Bronze Age, the Naples region of Italy had been a hub of agriculture and trade. But Sheridan says the Avellino eruption completely wiped that out for 200 years.

If history and science are any guide, Sheridan says his study shows Naples could be impacted by a massive Vesuvial eruption.

But he worries current disaster plans are not adequate to protect people who live in the volcano's shadow.

"Where would three million people go? And go where they would have to stay? They couldn't come back," he said. "And when would they go? They wouldn't want to go earlier than the cataclysm but there wouldn't be time if they waited until the last minute."