Pyroclastic Flow | John Seach

Pyroclastic Flows and Nuée ardentes are the most dangerous of all the volcanic eruption styles. Pyroclastic flows are clouds of hot gas, ash, and clasts which move down hill under the action of gravity. They can move at speeds of 100 km per hour and destroy everything in their path.

Mt Pelee produced a pyroclastic flow in 1902 which killed 29 000 people. Pyroclastic flows can be caused by column collapse, lava dome collapse, or boiling over of a vent like a pot of rice. Pyroclastic flows are driven by gravity and are channeled into valleys.

Distances travelled. Up to 100 km.
Speed of flows. 900 km/hr.
Temperature. 600-1100 deg C.

Pyroclastic flows are different to a Nuée ardente.

Pyroclastic flows are mostly associated with silicic volcanoes. Phreatomagmatic eruptions at basaltic volcanoes occasionally produce pyroclastic flows.