Low-level tremor at Veniaminof coincided with a pilot observation of a steam plume at 1230 on 1 August, prompting AVO to raise the Aviation Color Code to Yellow and the Volcano Alert Level to Advisory. On 2 August AVO noted that tremor had subsided, though low-level seismicity persisted at least through 6 August. Elevated surface temperatures were visible in satellite images. A small steam plume was also visible on 3 August.

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)