Mount Vesuvius spewed forth a deadly cloud of tephra and gases to a height of 33 kilometres (21 mi), ejecting molten rock, pulverized pumice and hot ash at the rate of 1.5 million tons per second, ultimately releasing a hundred thousand times the thermal energy of the Hiroshima-Nagasaki bombings. The total inhabitants of the cities were 16,000–20,000; the remains of about 1,500 people have been found at Pompeii and Herculaneum, but the overall death toll is still unknown.