AVO reported that on 22 February several minor ash bursts from Veniaminof were recorded by the seismic network and observed on web camera footage. The bursts rose to an altitude of below 2.7 km (9,000 ft) a.s.l. but fallout was confined to the crater. Sporadic increases in seismic activity were noted since 11 February, including tremor episodes that lasted 1-2 minutes and occurred several times per hour. The Aviation color code was raised to Yellow and the Alert Level was raised to Advisory. Steam plumes emitted from the intra-caldera cinder cone were seen on video footage during 23-25 February and seismic levels were elevated during 23-26 February.

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)