Mount Vesuvius spewed a deadly cloud of volcanic gas, stones, and ash to a height of 33 kilometres (21 mi), ejecting molten rock and pulverized pumice at the rate of 1.5 million tons per second, ultimately releasing a hundred thousand times the thermal energy of the Hiroshima bombing.[2] Several Roman settlements were obliterated and buried underneath massive pyroclastic surges and ashfall deposits, the most well known being Pompeii and Herculaneum