AVO reported that during 13-19 May seismicity from Redoubt had decreased from levels detected during 2-7 May, but remained above background levels. Rock avalanche events, discrete earthquakes, and minor volcanic tremor were evident in seismic data. Growth of the lava dome in the summit crater continued and vigorous steam emissions from the margins of the lava dome were seen on the web camera. Occasional rockfalls originating from unstable slopes of the lava dome produced minor ash clouds in the vicinity of the summit. Occasional incandescence was observed in nighttime images from the web camera. On 15 May, the volume of the dome was an estimated 30-60 million cubic meters. During an overflight on 16 May, scientists observed a turquoise lake along the S margin of the dome, and a hot, vigorous, and persistent fumarole on the W wall of the upper gorge. The Volcanic Alert Level remained at Watch and the Aviation Color Code remained at Orange.

Geological Summary. Redoubt is a glacier-covered stratovolcano with a breached summit crater in Lake Clark National Park about 170 km SW of Anchorage. Next to Mount Spurr, Redoubt has been the most active Holocene volcano in the upper Cook Inlet. The volcano was constructed beginning about 890,000 years ago over Mesozoic granitic rocks of the Alaska-Aleutian Range batholith. Collapse of the summit 13,000-10,500 years ago produced a major debris avalanche that reached Cook Inlet. Holocene activity has included the emplacement of a large debris avalanche and clay-rich lahars that dammed Lake Crescent on the south side and reached Cook Inlet about 3,500 years ago. Eruptions during the past few centuries have affected only the Drift River drainage on the north. Historical eruptions have originated from a vent at the north end of the 1.8-km-wide breached summit crater. The 1989-90 eruption had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano.

Source: US Geological Survey Alaska Volcano Observatory (AVO)