| Emplacement or flowage of hot pyroclastic rock debris on or into thick snowpacks on volcanoes can trigger hazardous rapid flows of sediment (including ice grains) and water. Such rapid flows can extend far beyond the flanks of a volcano, as has been observed at volcanoes in many parts of the world. Commonly these sediment-water flows achieve discharges and velocities that produce catastrophic consequences more than 100 kilometers downstream from source areas. The hazardous nature of such flows was most recently demonstrated in 1985 at Nevado del Ruiz volcano in Colombia, where snowmelt-generated sediment-water flows killed about 23,000 people. -- Pierson, 1997 |
