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This is a drawing of the 1631 eruption of Mt. Vesuvius.
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Image courtesy of: Dr. Boris Behncke. Artist: Giovan Batista Passaro This account of the eruption of Mt. Vesuvius was modified from the Vesuvio website.

The ad79 Eruption of Mt. Vesuvius

Around 1:00 pm on 24 August a tall cloud of steam and ash rose above Mt. Vesuvius and debris began to fall. In the area around Pompeii the thickness of falling debris increased by 6 to 8 inches per hour. The rocks which comprised the debris were up to 3 inches in diameter, and fell with a speed of up to 100 miles/hour. They may have caused injuries and isolated deaths, and should have, after a few hours, caused the collapse of roofs.

The city was soon covered in complete darkness, a phenomenon which is familiar to other populations involved in eruptions such as those at Mount St. Helens, and Mt. Pinatubo. The residents probably did not even know what kind of event was striking them, and waited in their homes, hoping that the shower of rock would sooner or later come to an end.

After 12 hours of continuous explosive activity, a change in the eruptive dynamics occurred. The mouth of the volcano widened such that local gas pressure could no longer push up the tall ash column. The mixture of gas and ash no longer rose up into the sky, but immediately fell back onto the slopes of the volcano, forming glowing avalanches of hot flowing material (perhaps 800 degrees) which rushed rapidly down slope, destroying everything in their paths. This change in the eruption proved fatal to the thousands of people around the volcano. The Roman towns of Pompeii and Herculaneum were destroyed in a matter of minutes.

Pompeii and Herculaneum were rediscovered in the 18th century with many treasures intact. The reconstruction of these cities gives a vivid idea of what Mt. Vesuvius is able to do.


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