Novarupta and the 1912 Katmai Eruption

Novarupta is a volcano on the Alaska Peninsula that erupted explosively from June 6 to 8, 1912, in the largest volcanic eruption of the 20th century. The event, long attributed to nearby Mount Katmai, buried the Ukak River valley in hot ash, creating the Valley of Ten Thousand Smokes, and led to the creation of Katmai National Monument in 1918 [1][2].

The Eruption

Earthquakes had grown more frequent and stronger for at least a week beforehand, and two families at Katmai Village left two days earlier. Skies darkened around 1 p.m. on June 6, and the sun was hidden for about 60 hours. The ash column rose above 100,000 feet, Kodiak Island was dark for nearly three days, and the ash cloud eventually encircled the Earth [1].

Volume and Ranking

About 3.1 cubic miles (13 cubic kilometers) of magma erupted, according to the National Park Service, and USGS estimates 15 cubic kilometers, about 30 times the volume of the 1980 Mount St. Helens eruption and about 230 years of Kilauea’s eruptions. The USGS describes it as the 20th century’s most voluminous eruption, spreading more fallout than all other historical Alaskan eruptions combined [1][2].

Novarupta and Mount Katmai

The eruption was long misattributed to Mount Katmai, about 10 km away, where most of the magma had been stored. Almost all of it vented at Novarupta, a vent about 1.2 miles wide with a lava dome 1,235 feet wide and 211 feet high, while Katmai’s summit collapsed as magma drained from beneath it. The resulting caldera is about 3 km wide and 600 m deep and has slowly filled with water since the late 1910s, now holding a lake more than 250 m deep [1][2].

Valley of Ten Thousand Smokes

Pyroclastic flows buried the Ukak River valley in thick hot ash and pumice, and snowfields and glacial streams flashed to steam. Robert F. Griggs, leading a National Geographic-funded expedition in 1916, saw tens of thousands of fumaroles and named the Valley of Ten Thousand Smokes. By the 1930s most had cooled [1]. Scientists did not reach the site until 1918 [2].

Effects on People and Places

Ash nearly buried Katmai Village, and a massive flood in 1916 destroyed what remained [1]. The ash fall devastated Kodiak Island’s life for 60 hours, and Southwest Alaska’s salmon industry was badly hurt from 1915 to 1919 [3]. See the entry on Kodiak Island.

Protection and Legacy

Griggs and the National Geographic Society lobbied for protection, and Katmai National Monument was created by presidential proclamation in 1918. Griggs published The Valley of Ten Thousand Smokes in 1922. In 1965 and 1966 NASA sent Apollo astronauts to the valley for geology training because its landscape resembled the lunar surface [1]. A 2010 satellite image showed wind-scoured ash from the eruption still blowing across Shelikof Strait [2]. See the entry on Katmai National Park and Preserve.

FAQs

When did Novarupta erupt? June 6–8, 1912.

Why is it called the Katmai eruption? It was long blamed on Mount Katmai, whose summit collapsed, but the magma vented at Novarupta.

What is the Valley of Ten Thousand Smokes? A valley buried by hot ash in 1912, named for its thousands of fumaroles.

How big was the eruption? About 13–15 cubic kilometers of magma, around 30 times Mount St. Helens in 1980.

When was Katmai National Monument created? In 1918.

Sources

1. National Park Service: Valley of Ten Thousand Smokes
2. U.S. Geological Survey: What was the largest volcanic eruption of the 20th century?
3. Wikipedia: Kodiak Island

Editorially reviewed by Specialty Digest Editorial TeamLast reviewed November 12, 2026Researched and drafted with AI assistanceReport an issue