How fast does a pyroclastic flow travel?

Pyroclastic flows travel away from a volcano's vent at speeds up to 150 kilometers per hour. They contain hot gas, ash and rock at temperatures ranging from 100 to 800 degrees Celsius.

Occurring when part of the eruption column collapses, a pyroclastic flow devastates everything in its path. It generally follows valleys or other low lying areas, but it can jump over water to land on the other side. The hot rock and ash burns everything directly in its path, and inhalation of the hot gas causes burns to the lungs and asphyxiation. Ignimbrites are pyroclastic flows of extremely high volume. They are produced during catastrophic eruptions, with deposits up to a few hundred meters thick.