AVO reported that during 7-11 August seismicity at Veniaminof remained above background levels. Cloud cover obscured views of the cinder cone inside the caldera during 7-8 August. Slightly elevated surface temperatures, consistent with cooling lava flows, were detected in partly cloudy satellite images during 9-10 August. On 11 August cloud cover prevented satellite image views, and web-camera views showed nothing significant. During 11-12 August seismic tremor increased and persistent elevated surface temperatures, consistent with lava effusion, were visible in satellite imagery. The web camera in Perryville (32 km SSE) recorded intermittent steam-and-ash plumes; one on 12 August rose 3.7 km (12,000 ft) a.s.l. and drifted W. Seismic tremor has remained high on 13 August. The Volcano Alert Level remained at Watch and the Aviation Color code remained at Orange.

Geological Summary. Veniaminof, on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

Source: US Geological Survey Alaska Volcano Observatory (AVO)