Remarques sur l'eruption du Katmai et de la Vallee des Dix-Mille-Fumees et sur le probleme des ignimbrites

Abstract

Abstract During the eruption of Mt. Katmai, June 1912, about 15 cu km of volcanic ejecta, since named "Katmai tuffs", was deposited. Recent field and laboratory work shows that this is ignimbritic dacite. The eruption can be reconstructed despite lack of direct observation. Accompanied by violent earthquakes, the ignimbrites, passing through a foamy stage before being pulverized, issued from fissures at the head of the Valley of Ten Thousand Smokes and fell in the valley like snow over about 20 km to a thickness exceeding 100 m. The ignimbrites were then covered by about 10 cu km of ash which erupted from the caldera of Mt. Katmai. The whole eruption lasted 16 hours. Thie is the only known historic case of ignimbrite formation.