What was the largest volcanic eruption in the 20th century?
The largest eruption in the world in the 20th century occurred in 1912 at Novarupta on the Alaska Peninsula. An estimated 15 cubic kilometers of magma was explosively erupted during 60 hours beginning on June 6th. This volume is equivalent to 230 years of eruption at Kilauea (Hawaii) or about 30 times the volume erupted by Mount St. Helens (Washington) in 1980!
Due to the remote location of the eruption, scientists did not visit the site until 1918, when they found the Ukak River valley filled with volcanic deposits and steaming fumaroles. They called it the "Valley of Ten Thousand Smokes".
Fumaroles are openings in the earth’s surface that emit steam and volcanic gases, such as sulfur dioxide and carbon dioxide. They can occur as holes, cracks, or fissures near active volcanoes or in areas where magma has risen into the earth’s crust without erupting. A fumarole can vent for centuries or quickly go extinct, depending on the longevity of its heat source.
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
- Volcanoes: Monitoring Volcanoes
- Volcanoes: National Volcano Early Warning System
- Volcanoes: Science for Public Safety
Bill Burton discusses the June 6-8, 1912 eruption of Mount Katmai in Alaska which was 30 times larger than the eruption of Mt. St. Helens in 1980. This eruption caused widespread devastation, and inspired heroic efforts at survival by the local people. Burton returns to this topic a century later and explains what lessons the Mount Katmai eruption provides for modern-day monitoring of volcano hazards.
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon. Spectacular debris flow footage, recorded by Franck Lavigne of the Universite Paris, makes clear the destructive power of these flows.
Volcanic ash is geographically the most widespread of all volcanic hazards. USGS geologist Larry Mastin describes how volcanic ash can disrupt lives many thousands of miles from an erupting volcano. The development of ash cloud models and ash cloud disruption to air traffic is highlighted.
USGS technologist Rick LaHusen describes how the development and deployment of instruments plays a crucial role in mitigating volcanic hazards.
USGS geologist, Angie Diefenbach, describes how she uses GIS, (Geographic Information Systems) software to study volcanic eruptions and their impacts on society.
View southeast from Overlook Cabin looking over the Valley of Ten Thousand Smokes. The pyroclastic and ash deposits that fill the valley remain nearly vegetation-free more than 100 years after the 1912 Novarupta-Katmai eruption.
Volcanic ash drifts around houses at Katmai after the June 1912 eruption of Novarupta Volcano. Church in the distant background. August 13, 1912.