Novarupta, also called Katmai-Novarupta, volcanic vent and lava dome, southern Alaska, U.S., located at an elevation of 841 metres (2,759 feet) within Katmai National Park and Preserve. Its violent eruption, which began on June 6, 1912, and lasted 60 hours, is considered the largest volcanic eruption of the 20th century. Novarupta is a Latin word meaning “new break.”

Novarupta lava dome Novarupta, a lava dome in southern Alaska, was formed in June 1912, when tremendous amounts of ash, molten rock, and sulfur aerosols erupted from a vent near Mount Katmai. Gene Iwatsubo/U.S. Geological Survey

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Over the course of the event, Novarupta ejected about 28 cubic km (about 6.7 cubic miles) of tephra (ash particles that later fall) some 32 km (20 miles) into the stratosphere. Ash fell in amounts up to 30 cm (1 foot) deep over an area of almost 7,800 square km (about 3,000 square miles) and transformed a nearby vast green valley into a wasteland known as the Valley of Ten Thousand Smokes. Inside this area, pyroclastic flows filled the V-shaped valley of Knife Creek with more than 200 metres (about 660 feet) of ash and rock in some places. Falling ash also buried the town of Kodiak, Alaska, some 160 km (100 miles) away. About one hour after the initial, massive blast occurred, residents of Juneau, Alaska, some 1,200 km (750 miles) away from Novarupta, reported hearing the sound. The eruption nearly leveled Broken Mountain and Baked Mountain and depleted material stored in Novarupta’s magma chamber, as well as that of Mount Katmai nearly 10 km (6 miles) away, which caused the later to sink by several hundred feet into a newly formed 800-metre- (roughly 2,600-foot-) deep caldera.

Within days of the blast, the ash plume extended over western Canada and several western U.S. states. By June 17th it had traveled to Algeria. Ash, dust, and sulfuric aerosols from the 1912 blast are thought to have produced a drought in China and weakened the summer monsoon in India the following year. Although no one died as a result of the eruption, the choking ash devastated much of the plant and animal life in southern Alaska, including the salmon fishery, which did not fully recover until 1919. Several native villages on the Katmai Peninsula were abandoned permanently after the eruption. Novarupta wiped out the region’s mosquito population, and tens of thousands of mammals and birds are thought to have perished from starvation and from respiratory distress caused by falling ash.