AVO reported that the eruption of lava at Great Sitkin’s summit lava dome continued during 24-30 January, confirmed by satellite data acquired during the week. Effusion was concentrated at the center of the dome with minimal advancement at the margins of the flow. The center of the dome uplifted and caused radial cracks; a new lobe of lava extruded from the northernmost crack and traveled 180 m NW of the vent by 24 January. Weakly elevated surface temperatures were identified in satellite data during 24-26 January. Cloudy weather sometimes prevented satellite views of the volcano. Local webcams and seismic data communications that were offline due to a storm-related power failure came back online on 28 January; infrequent, small volcanic earthquakes were detected during 29-30 January. The Volcano Alert Level remained at Watch (the third highest level on a four-level scale) and the Aviation Color Code remained at Orange (the third highest color on a four-color scale).

Geological Summary. The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an older edifice and produced a submarine debris avalanche. Deposits from this and an even older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Eruptions have been recorded since the late-19th century.

Source: US Geological Survey Alaska Volcano Observatory (AVO)