On this day in 79 A.D., after centuries of dormancy, Mount Vesuvius erupts in southern Italy. The massively cataclysmic event destroyed the prosperous Roman cities of Pompeii and Herculaneum and killed thousands.The cities, buried under a thick layer of volcanic material and mud, were never rebuilt and largely forgotten in the course of history for one and one-half millennia.
In 1592, architect Domenico Fontana struck upon the “re-discovery” of Pompeii while digging an underground aqueduct to the mills of Torre Annunziata, unearthing walls with paintings and inscriptions. Through the 18th century, and into the modern era, Pompeii and Herculaneum were further excavated by Italian, Spanish and French engineers and archeologists, providing an unprecedented record of the everyday life of an ancient civilization, startlingly preserved in sudden death. Pompeii supported between 10,000 and 20,000 inhabitants at the time of its destruction, and but for a significant earthquake in 62 A.D., no eruption, flows or other volcanic activity had signaled the coming conflagration.
Just after midday on August 24, 79 A.D., fragments of ash, pumice, and other volcanic debris began pouring down on Pompeii, quickly covering the city to a depth of more than 9 feet and causing the roofs of many houses to fall in.The eruption ejected a cloud of stones, ashes and volcanic gases to a height of 21 miles, spewing molten rock and pulverized pumice at the rate of 7.8×105 cubic yards per second, ultimately releasing a hundred thousand times the thermal energy released by the Hiroshima-Nagasaki bombings. Surges of pyroclastic material and heated gas, known as nuées ardentes, reached the city walls on the morning of August 25 and soon asphyxiated those residents who had not been killed by falling debris.
Additional pyroclastic flows and rains of ash followed, adding at least another 9 feet of debris and preserving in a pall of ash the bodies of the inhabitants who perished while taking shelter in their houses or trying to escape toward the coast or by the roads leading to Stabiae or Nuceria. Thus Pompeii remained buried under a layer of pumice stones and ash 19 to 23 feet deep. The city’s sudden burial served to help protect it for the next 17 centuries from vandalism, looting, and the destructive effects of climate and weather.
Exact casualty numbers are unknown, but the only surviving eyewitness account of the event consists of two letters by Pliny the Younger to the historian Tacitus, in which Pliny writes “Darkness fell, not the dark of a moonless or cloudy night, but as if the lamp had been put out in a dark room.”