pyroclastic surge

A pyroclastic surge is a dangerous volcanic phenomenon characterized by a fast-moving, ground-hugging cloud of hot rock fragments, gases, and air. These surges, also known as nuées ardentes or glowing avalanches, can reach speeds of up to 160 km per hour (100 miles per hour) and temperatures between 100 and 700 °C (212 to 1,300 °F). They are a product of explosive volcanic eruptions, where the violent expansion of gases shatters magma into small particles. Pyroclastic flows can pour over vent edges or form when an ash column collapses. They are extremely destructive, incinerating nearly everything in their path and can bury landscapes under thick deposits.12