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Report on Montagu Island (United Kingdom) — September 2005

Montagu Island

Bulletin of the Global Volcanism Network, vol. 30, no. 9 (September 2005)
Managing Editor: Richard Wunderman.

Montagu Island (United Kingdom) September 2005 satellite image and infrared data portray ongoing eruption

Please cite this report as:

Global Volcanism Program, 2005. Report on Montagu Island (United Kingdom) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 30:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200509-390081

Montagu Island

United Kingdom

58.445°S, 26.374°W; summit elev. 1370 m

All times are local (unless otherwise noted)

The first recorded eruption of Mt. Belinda volcano (Montagu Island), which began around 20 October 2001, continued (as reported in BGVN 28:02, 29:01, 29:09, 29:10) until at least the latter part of 2005. Information for the following report was prepared and submitted by Matt Patrick of the Hawai'i Institute of Geophysics and Planetology (HIGP) and John Smelie of the British Antarctic Survey, with the assistance of the HIGP Thermal Alerts Team.

This eruption was detected by the MODVOLC automated satellite detection system, which scans for anomalous thermal activity in MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data over the entire Earth approximately twice per day (Wright and others, 2004). Investigators acquired a recent, 23 Sept 2005, cloud-free ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) image (15-30 m pixel size), which provided valuable information on a new phase of activity. It revealed a larger effusive eruption than previously identified in satellite imagery of Montagu Island (figure 9).

Figure (see Caption) Figure 9. ASTER image showing Montagu Island's Mount Belinda on 23 September 2005. Courtesy of HIGP Thermal Alerts Team.

Based on frequent MODVOLC alerts (figure 10) and occasional high-resolution satellite data (ASTER, IKONOS, and Quickbird), Mount Belinda has maintained persistent activity since the start of the eruption. Activity has consisted of continuous steaming and low-intensity explosive events at the summit (presumably Strombolian), producing low-level ash plumes and ubiquitous tephra deposits on the island's ice cover, and at least three distinct effusive events. Several satellite images were posted by HIGP on the National Aeronautics and Space Administration (NASA) Earth Observer website, 13 October 2004 and 19 October 2005.

Figure (see Caption) Figure 10. (A) Chronological graph of radiant heat output from Mount Belinda measured from satellite sensors. The date range depicted along the x-axis of this graph is from late 2001 to September 2005. (B) A plot showing the distance of satellite-measured thermal anomaly pixels from the Mount Belinda vent during the period 2001 to September 2005. Courtesy of HIGP Thermal Alerts Team.

Scientists noted an intense shortwave-IR anomaly at the summit of Mt. Belinda in all cloud-free ASTER images acquired throughout the eruption. This suggested the presence of a lava lake in the summit crater (see Patrick and others, 2005, for more detailed information on the eruption).

Far from slowing down, the activity throughout 2005 marked the highest levels yet registered by MODVOLC (figure 10a). For the first time in 2005, radiant heat output exceeded 150 MW (see Wright and Flynn, 2004, and Wright and others, 2005, for calculation details).

By plotting the position of each anomalous MODVOLC pixel relative to the central vent (figure 10b) one can see that most pixels are within 1 km of the vent. This reflects the approximate scale of MODIS pixels and thus the inherent level of location ambiguity (note, however, these results fail to show the 2-km-long lava flow emplaced in mid-2003 — see BGVN 29:01).

For the first time during this eruption, anomalous pixels began appearing more than 2 km away from the central vent on the satellite image for 0100 UTC on 15 September 2005, some up to 3.3 km away (figure 10b). This suggested the presence of a ~ 3 km long lava flow. Corroborating this was the ASTER image from 23 September 2005 (figure 9), which indicated heightened activity and a 3.5-km long lava flow extending from the summit cone of Mt. Belinda into the sea. A steam plume originated in the vicinity of the ocean entry. Note that the steam plume appears to drift W from its origin (where the plume is whitest), while the ash plume from the summit of Mt. Belinda (1,370 m elev.) drifts E, indicating varying wind directions at different elevations.

The lava flow initially traveled NE from the vent, but farther on it ran into a rocky arete, which diverted its path to due N. A 90-m-wide lava channel is visible at a distance of 1 km from the summit. The flow appears to be covered (perhaps entering a tube) within its first kilometer, where no anomalous shortwave IR pixels exist. It is unlikely that the flow is subglacial in this first kilometer, as its path is coincident with emplacement of the previously mentioned lava flow of mid-2003, which was 2 km long and had already melted ice along this route.

At the request of the British Antarctic Survey, the Royal Air Force sent an airplane from the Falkland Islands on 11 October 2005. The plane encountered cloudy conditions but those on board recognized steam rising from the sea. This flight took place prior to study of the 23 September ASTER image and thus it marked the first observation that lava reached the sea.

References. Patrick, M., Smellie, J.L., Harris, A.J.L., Wright, R., Dean, K., Izbekov, P., Garbeil, H., and Pilger, E., 2005, First recorded eruption of Mount Belinda volcano (Montagu Island), South Sandwich Islands: Bulletin of Volcanology, v. 67, p. 415-422.

Wright, R., and Flynn, L.P., 2004, A space-based estimate of the volcanic heat flux into the atmosphere during 2001 and 2002: Geology, v. 32, p. 189-192.

Wright, R., Flynn, L.P., Garbeil, H., Harris, A.J.L., and Pilger, E., 2004, MODVOLC: near-real-time thermal monitoring of global volcanism: Journal of Volcanology and Geothermal Research, v. 135, p. 29-49.

Wright, R., Carn, S., and Flynn, L.P., 2005, A satellite chronology of the May-June 2003 eruption of Anatahan volcano: Journal of Volcanology and Geothermal Research, v. 146, p. 102-116.

Geological Summary. 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 11 x 15 km island rises about 3,000 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 peak at the SE tip of the island, was the source of lava flows exposed at Mathias Point and Allen Point. There was no record of Holocene activity until MODIS satellite data, beginning in late 2001, revealed thermal anomalies consistent with lava lake activity. Apparent plumes and single anomalous pixels were observed intermittently on AVHRR images from March 1995 to February 1998, possibly indicating earlier volcanic activity.

Information Contacts: Matt Patrick, University of Hawaii, Hawaii Institute of Geophysics and Planetology (HIGP) Thermal Alerts Team, 2525 Correa Road, Honolulu, HI 96822 (URL: http://modis.higp.hawaii.edu/); John Smelie, British Antarctic Survey, Natural Environment Research Council, High Cross, Madingly Road, Cambridge CB3 0ET, United Kingdom (URL: https://www.bas.ac.uk/); NASA Earth Observer (URL: http://earthobservatory.nasa.gov/NaturalHazards/).