Report on Gareloi (United States) — 28 July-3 August 2021
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
28 July-3 August 2021
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2021. Report on Gareloi (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 28 July-3 August 2021. Smithsonian Institution and US Geological Survey.
51.79°N, 178.794°W; summit elev. 1573 m
All times are local (unless otherwise noted)
AVO reported that the elevated seismicity first detected at Gareloi in May had continued through June and then declined to background levels. On 28 July the Aviation Color Code was lowered to Green and the Volcano Alert Level was lowered to Normal.
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.