What was the largest volcanic eruption in the 20th century?

The World's largest eruption of 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."

Learn moreThe Novarupta-Katmai eruption of 1912 - largest eruption of the twentieth century; centennial perspectives

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What is a supervolcano? What is a supereruption?

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What was the most destructive volcanic eruption in the history of the United States?

The May 18, 1980 eruption of Mount St. Helens (Washington) was the most destructive in the history of the United States. Novarupta (Katmai) Volcano in Alaska erupted considerably more material in 1912, but owing to the isolation and sparse population of the region, there were no human deaths and little property damage. In contrast, the eruption of...

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video thumbnail: Volcano Hazards
July 30, 2012

Volcano Hazards

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.

Video Sections:

  • Volcanoes: Monitoring Volcanoes
Severe ash in Kodiak, Alaska, the day after the eruption of Katmai ...

Severe ash in Kodiak, AK, day after eruption of Katmai Volcano, 1913

Severe ash in Kodiak, Alaska, the day after the eruption of Katmai Volcano, 1912.

video thumbnail: The 20th Century's Greatest Volcanic Eruption- Mt Katmai 100 Years Later 
June 5, 2012

The 20th Century's Greatest Volcanic Eruption- Mt Katmai 100 Years Later 

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

Attribution: Natural Hazards
May 9, 2012

Volcano Web Shorts 4 - Instruments

USGS technologist Rick LaHusen describes how the development and deployment of instruments plays a crucial role in mitigating volcanic hazards.

May 9, 2012

Volcano Web Shorts 5 - Volcanic Ash Impacts

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.

May 9, 2012

Volcano Web Shorts 2: Debris Flows

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

Image: Valley of Ten Thousand Smokes, Alaska
June 9, 1991

Valley of Ten Thousand Smokes, Alaska

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.

Attribution: Region 11: Alaska
Photograph of many steaming fumaroles on a broad plain surrounded by mountains
December 31, 1922

Valley of Ten Thousand Smokes, Katmai, Alaska, circa 1922

Valley of Ten Thousand Smokes in Katmai National Park, circa 1922. Windy Creek is in the foreground. Following the June 6, 1912 eruption of Novarupta-Katmai, thousands of fumaroles filled the valley for many years. Buried snow fields, glacial streams, and precipitation were converted to steam by the heat trapped in the pyroclastic flow. Learn more in USGS Professional

Image: Katmai National Park and Preserve, Alaska
August 13, 1912

Katmai National Park and Preserve, Alaska

Volcanic ash drifts around houses at Katmai after the June 1912 eruption of Novarupta Volcano. Church in the distant background. August 13, 1912.

Attribution: Region 11: Alaska
Katmai National Park and Preserve, Alaska. Ash drifts around houses...
August 13, 1912

Katmai National Park and Preserve, AK. Ash drifts around houses at ...

Katmai National Park and Preserve, Alaska. Ash drifts around houses at Katmai after the June 1912 eruption of Novarupta Volcano. Ash slide on the mountain in the background.

June 6, 2012

PubTalk 6/2012 — Exploring The Valley of Ten Thousand Smokes

-- a Centennial perspective of the Novarupta-Katmai eruption, the largest of the 20th century

By Judy Fierstein, USGS


  • 100 years ago on June 6, a 3-day explosive eruption at Novarupta on the Alaska Peninsula created the spectacular Katmai caldera and the Valley of Ten Thousand Smokes, called the eighth wonder of the
Attribution: Region 11: Alaska