By the time Vesuvius stopped belching poisonous gas, the bustling city of Pompeii was silent, completely buried by volcanic ash and debris. It remained silent for seventeen hundred years.
When the mountain first erupted that August afternoon, volcanic ash and pumice initially rained-on surrounding areas. Centuries later, scientists can distinguish the various layers of debris.
Pompeii, however, was not destroyed because of pumice debris. In fact, human remains found above the ash and pumice layers indicate people came back to their homes after the ashfall stopped. They could not have realized that by returning they placed themselves, and their children, into death’s path.
Annihilation of the town, and its people, occurred hours later when Vesuvius spewed out pyroclastic surges and pyroclastic flows. A pyroclastic flow first moves into canyons and river beds. At the bottom of the volcano, it can sweep away (or bury) anything in its path, including populated areas.
A surge can turn pristine lakes and forests into moonscapes. A pyroclastic flow can bury surrounding areas to depths of 50 to 200 meters (about 160 to 650 feet).
Nothing standing in its way will survive. That’s what happened to Pompeii and the neighboring town of Herculaneum.