Volcano Hazards

On May 18, 1980, at Mount St. Helens, data shows that an estimated 7-20 seconds elapsed between the triggering earthquake and the onset of the flank collapse. During the next 15 seconds, first one large block slid away, then another large block began to...
Yes. Crater lakes atop volcanoes are typically the most acid, with pH values as low as 0.1 (very strong acid). Normal lake waters, in contrast, have relatively neutral pH values near 7.0. The crater lake at El Chichon volcano in Mexico had a pH of 0.5 in...
Yes. Encounters between aircraft and clouds of volcanic ash are a serious concern. Jet engines and other aircraft components are vulnerable to damage by fine, abrasive volcanic ash, which can drift in dangerous concentrations hundreds of miles downwind...
Not usually. Earthquakes associated with eruptions rarely exceed magnitude 5, and these moderate earthquakes are not big enough to destroy the kinds of buildings, houses, and roads that were demolished in the movie. The largest earthquakes at Mount St....
Lahars are commonly initiated by: 1) large landslides of water-saturated debris, 2) heavy rainfall eroding volcanic deposits, 3) sudden melting of snow and ice near a volcanic vent by radiant heat or on the flanks of a volcano by pyroclastic flows, or 4...
Lahars can be of any size. They may be as small as several centimeters wide and deep, flowing less than one meter per second. Steep, unvegetated slopes during a heavy rain are often good sites to observe such small flows. At the other extreme, they can...
Pyroclastic flows can be extremely destructive and deadly because of their high temperature and mobility. During the 1902 eruption of Mont Pelee (Martinique, West Indies), for example, a nuee ardente demolished the coastal city of St. Pierre, killing...
Volcanic eruptions are one of Earth's most dramatic and violent agents of change. Not only can powerful explosive eruptions drastically alter land and water for tens of kilometers around a volcano, but tiny liquid droplets of sulfuric acid erupted into...