Science glossary film: Pyroclastic flows

Fast-moving ground-level flows of hot gases and rock fragments, dust and ash from a volcanic eruption. They can reach speeds of several hundred kilometres per hour, with temperatures of up to 1000°C. It was pyroclastic flows, rather than falling ash, that engulfed and destroyed the Roman cities of Pompeii and Herculaneum.

They can reach speeds of several hundred kilometres per hour, with temperatures of up to 1000°C. It was pyroclastic flows, rather than falling ash, that engulfed and destroyed the Roman cities of Pompeii and Herculaneum.