The world's largest volcanic eruption of the 20th century broke out at Novarupta in June 1912, filling with hot ash what came to be called the Valley of Ten Thousand Smokes and spreading downwind more fallout than all other historical Alaskan eruptions combined. Although almost all the magma erupted at the Novarupa vent, most of it was stored beneath Mount Katmai, 10 km away. Mount Katmai collapsed during the eruption. Airborne ash from the 3-day event blanketed all of southern Alaska, and its gritty fallout was reported as far away as Dawson, Ketchikan, and Puget Sound. Volcanic dust and sulfurous aerosol were detected within days over Wisconsin and Virginia; within 2 weeks over California, Europe, and North Africa; and in latter-day ice cores recently drilled on the Greenland ice cap.

Much of the material we will present is taken from the many detailed publications by geologists Wes Hildreth and Judy Fierstein of the U.S. Geological Survey. We refer interested followers to their publications, especially "The Novarupta-Katmai eruption of 1912: Largest eruption of the twentieth century: Centennial perspectives" for more detail and citations to original accounts.

Timeline of Novarupta-Katmai events
Selected references and articles
Related videos
View a slideshow of Katmai volcanic cluster images

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