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Report on Great Sitkin (United States) — 21 December-27 December 2022


Great Sitkin

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 21 December-27 December 2022
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2022. Report on Great Sitkin (United States) (Sennert, S, ed.). Weekly Volcanic Activity Report, 21 December-27 December 2022. Smithsonian Institution and US Geological Survey.

Weekly Report (21 December-27 December 2022)

Great Sitkin

United States

52.076°N, 176.13°W; summit elev. 1740 m

All times are local (unless otherwise noted)


AVO reported that satellite data acquired on 22 December confirmed that the lava flow field at Great Sitkin was advancing E. Slow lava effusion likely continued during 23-27 December, though nothing significant was visible in sometimes cloudy satellite images or detected in seismic data. Elevated surface temperatures were identified in satellite images during 21-23 and 25-27 December. The Volcano Alert Level remained at Watch (the second highest level on a four-level scale) and the Aviation Color Code remained at Orange (the second highest level 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)