AVO reported that unrest continued at Gareloi during 14-20 February. Seismicity remained elevated and was characterized by volcanic earthquakes and semi-continuous tremor, though after 16 February levels began to decline and only periods of seismic tremor were reported. Minor steaming was identified in webcam and satellite images on 14 February. The Volcano Alert Level remained at Advisory (the second lowest level on a four-level scale) and the Aviation Color Code remained at Yellow (the second lowest color on a four-color scale).

Geological Summary. The 8 x 10 km Gareloi Island, the northernmost volcano of the Delarof Group at the western end of the Andreanof Islands, consists of a stratovolcano with two summits and a prominent SE-trending fissure. The fissure was formed during an eruption in 1929 and extends from the southern summit to the sea. Steep sea cliffs that are cut into rocks of an older, eroded center are found on the SW coast, and submarine deposits of three debris avalanches produced by edifice collapse are found offshore. Young lava flows cover the older volcano from the summit to the coast along three broad axes trending NW, ENE, and S. The 1929 eruption originated from 13 craters along a 4-km-long fissure. Phreatic explosions were followed by the ejection of glassy pumice, lapilli, scoria, and older blocks, as well as by the emission of four short, steep lava flows, one of which reached the SE coast.

Source: US Geological Survey Alaska Volcano Observatory (AVO)