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Report on Novarupta (United States) — 17 September-23 September 2003


Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
17 September-23 September 2003
Managing Editor: Gari Mayberry

Please cite this report as:

Global Volcanism Program, 2003. Report on Novarupta (United States). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 17 September-23 September 2003. Smithsonian Institution and US Geological Survey.

Weekly Report (17 September-23 September 2003)


United States

58.27°N, 155.157°W; summit elev. 841 m

All times are local (unless otherwise noted)

According to the National Weather Service, strong winds on 21 September in the Katmai area picked up old, loose volcanic ash and carried it E over Kodiak Island. AVO received reports that some of this material fell in Kodiak. This was not the result of volcanic activity and no eruption occurred. Re-suspended volcanic ash should be considered as hazardous as primary volcanic ash, and a threat to aircraft. The volcanoes in the Katmai cluster remained at Concern Color Code Green.

Geological Summary. Novarupta, the least topographically prominent volcano in the Katmai area, was formed during a major eruption in 1912. This eruption was the world's largest during the 20th century and produced a voluminous rhyolitic airfall tephra and the renowned Valley of Ten Thousand Smokes (VTTS) ash flow. At the end of the eruption a small, 65-m-high, 400-m-wide lava dome grew to an elevation of 841 m within the source vent of the VTTS ashflow, a 2-km-wide area of subsidence NW of Trident volcano. The NE side of the Falling Mountain lava dome of the Trident volcanic cluster, as well as Broken Mountain and Baked Mountain, was removed by collapse of the Novarupta depression, which is marked by radial and scalloped arcuate fractures. Much larger collapse took place at Katmai volcano, 10 km to the east, where a 3 x 4 km wide caldera formed in response to magma reservoir drainage toward Novarupta.

Source: US Geological Survey Alaska Volcano Observatory (AVO)