Novarupta, Alaska, USA

Volcano Type:      Caldera
Volcano Status:    Historical
Last Known Eruption:     1912
Summit Elevation:     841 m     2,759 feet
Latitude:     58.27°N     58°16’0″N
Longitude:     155.157°W     155°9’24″W

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.

Novarupta Volcano (Kara Stenberg)

The Novarupta dome is about 400 m in diameter and 65 m high at its center, and is surrounded by a 2-km-wide, funnel-shaped structure. The surface of the dome is completely fractured into chaotic blocks and crumble breccia. The dome is a plug-like feature emplaced within a low ejecta ring. Prominent scarps along the flanks of Baked, Falling, and Broken Mountains surrounding the Novarupta depression indicate considerable subsidence occurred following the 1912 eruption. Nearby stratovolcanoes form a volcanic front trending N65E; Novarupta lies about 4 km behind the front. Linear fractures normal to the front extend between Novarupta and Trident.

An area of the Novarupta Volcano

An area of the Novarupta Volcano

A 65-m-high, 380-m-wide lava dome lies within a circular ejecta ring and caps the 1912 vent of Novarupta volcano. A 60-hour-long eruption beginning on June 6, 1912, the Earth’s largest eruption during the 20th century, produced The Valley of Ten Thousand Smokes ash-flow deposit, which forms the flat ground at the right. The face of Falling Mountain, behind Novarupta dome, was sheared off by a 2-km-wide collapse around the Novarupta vent.

Steaming area of the volcano (Ranger Jeanne)

Steaming Novarupta Volcano (Kara Stenberg)

Originally posted 2010-08-18 04:27:33.