Vesuvius Erupted, but When Exactly?

During the first 17 hours, Dr. Scarpati said, Pompeii was blanketed with pumice lapilli from the column, which fluctuated like a giant fountain through 12 distinct pulses. At 2 p.m., the volcano began to spew pumice mixed with gas. Over the next four hours, roofs began to cave in under the weight of the pumice lapilli, causing some supporting walls to crumble as well. After 17 hours, the debris in Pompeii was up…