Report on Montagu Island (United Kingdom) — 12 October-18 October 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 12 October-18 October 2005
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2005. Report on Montagu Island (United Kingdom). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 12 October-18 October 2005. Smithsonian Institution and US Geological Survey.
58.445°S, 26.374°W; summit elev. 1370 m
All times are local (unless otherwise noted)
An ASTER satellite image from 23 September showed a 3.5-km-long lava flow extending from the summit of Montagu Island (Mt. Belinda) into the sea. This was the largest effusive event observed during the 4-year-old eruption. Based on MODVOLC alerts, the flow appeared to have started sometime between 10 and 14 September. A conspicuous 90-m-wide channel was visible ~1 km from the vent. The image also showed a steam plume at the location of the ocean entry, and an ash-rich plume extending NE from the volcano's summit.
Geologic Background. The largest of the South Sandwich Islands, Montagu consists of a massive shield volcano cut by a 6-km-wide ice-filled summit caldera. The summit of the 10 x 12 km wide island rises about 3000 m from the sea floor between Bristol and Saunders Islands. Around 90% of the island is ice-covered; glaciers extending to the sea typically form vertical ice cliffs. The name Mount Belinda has been applied both to the high point at the southern end of the summit caldera and to the young central cone. Mount Oceanite, an isolated 900-m-high peak with a 270-m-wide summit crater, lies at the SE tip of the island and was the source of lava flows exposed at Mathias Point and Allen Point. There was no record of Holocene or historical eruptive activity until MODIS satellite data, beginning in late 2001, revealed thermal anomalies consistent with lava lake activity that has been persistent since then. Apparent plumes and single anomalous pixels were observed intermittently on AVHRR images during the period March 1995 to February 1998, possibly indicating earlier unconfirmed and more sporadic volcanic activity.