Report on Great Sitkin (United States) — 9 March-15 March 2022
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
9 March-15 March 2022
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2022. Report on Great Sitkin (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 9 March-15 March 2022. Smithsonian Institution and US Geological Survey.
52.076°N, 176.13°W; summit elev. 1740 m
All times are local (unless otherwise noted)
AVO reported that slow lava effusion at Great Sitkin continued during 8-15 March and very low seismicity persisted. The rate of effusion slightly increased from 28 February to 11 March, based on radar data collected on those two dates; lava was extruded in all direction from the vent and the southern lobe advanced 20 m. Snow covered most of the flow except for the advancing fronts of the lava lobes and around the vent area. Elevated surface temperatures were periodically identified in satellite images. Minor steaming was visible in webcam images on 12 March. The steaming was dense and also visible in satellite images during 12-13 March. The Aviation Color Code and the Volcano Alert Level remained at Orange and Watch, respectively.
Geological Summary. The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic 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 ancestral volcano and produced a submarine debris avalanche. Deposits from this and an 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. Historical eruptions have been recorded since the late-19th century.