for National Geographic News
On the volcanic plains east of Naples, Italy, archaeologists have made an unusual discovery: thousands of prehistoric footprints in a layer of volcanic ash.
The footprints were made when the cooling ash was still fresh. And they're all headed in the same direction: away from Italy's infamous volcano, Vesuvius.
These footprints are just one of several archaeological finds indicating that the still-active Vesuvius is capable of far worse eruptions than anything disaster planners in nearby Naples are currently prepared for.
Vesuvius is best known as the volcano that buried the ancient Roman towns of Pompeii and Herculaneum in A.D. 79 (see photo).
But the newly found footprints date to a prior eruption approximately 3,800 years ago.
Nobody knows how many people lived in the area at that time, but it might have been as many as 10,000, says Michael Sheridan, a geologist at the University at Buffalo, the State University of New York.
What is known is that everyone left in a hurry when the mountain erupted.
Sheridan coauthored a report on the findings that will appear this week in the Proceedings of the National Academy of Sciences.
Naples at Risk
Geologists had known about the earlier Vesuvius eruption for decades, but it's only now that they're beginning to realize its scale.
"It disrupted a huge Bronze Age population," Sheridan said. The blast, he says, emitted four times as much ash and pumice as did the 1980 eruption of the United States's Mount St. Helens.
Furthermore, while the volcano had probably been stirring for some time, the main eruption caught the ancient community by surprise.
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