During its eruption in 79 AD, Mt. Vesuvius spewed 1.5 million tons of lava per second. SubjectsHistory FactsFactsIP FactoidsScary Facts by IP Factly - Feb 25, 2016 Mt. Vesuvius by Ωméga/CC BY-SA 2.0 That’s the equivalent of the weight of about 250,000 fully grown elephants! It is no wonder then that the eruption was able to bury two cities – Pompeii and Herculaneum, killing at least 16,000 people.