Satellite imagery from 7 December 2003 showed that low-level ash emission and lava effusion had persisted steadily at Montagu Island (Mount Belinda) for the past 2 years. A NE-trending, 2-km-long lava flow was emplaced on the summit ice shelf in July 2003, and ash continued to blanket the eastern side of the island. The automated MODVOLC satellite monitoring system indicated that total heat output from the volcano reached its highest intensity in October 2003.

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.

Source: Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts Team