AVO reported that the eruption at Veniaminof continued during 17-23 March. Low surface temperatures were visible in satellite images along with steam-and-gas plumes. Low-level tremor was recorded in local seismic data. During the morning of 21 March small explosions were identified using seismic data and infrasound sensors in Chignik Lagoon. A volcanic gas cloud drifted SE at or below 1.5 km (5,000 ft) a.s.l. Small explosions were detected again during 21-23 March. Sulfur dioxide plumes were identified in satellite data. Minor ash emissions rose hundreds of meters and rapidly dissipated, though on 23 March a pilot saw an ash plume rise to 3 km (10,000 ft) a.s.l. Satellite data during 22-23 March showed highly elevated surface temperatures and subsidence of the glacial ice over the flank vent where lava was erupting. 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)