*************************************************************** Montserrat Volcano Observatory Weekly Report for the period 2 - 9 January 2009 *************************************************************** Activity at the Soufrière Hills Volcano increased drastically on Friday 2 and culminated on Saturday 3 January in the morning with 2 energetic explosions. Since then, the level of activity has dropped significantly and background activity remained very low over the week. On Friday 2, an energetic pyroclastic flow and associated surge went down Tyers Ghaut (NW of the volcano) and reached the upper part of the Belham river, near Lee's (NE from St Georges Hill) at 02:29pm local time (LT). After a period of heightened seismic activity, two main explosions occurred on Saturday 3 at 04:47am and 07:07am LT. Both explosions had a significant jet component reaching at least 500 m above the dome and the plume reached heights over 35,000 feet (~11 km) above sea level. Ash fall affected most of the island due to southwards winds from 4,000 feet (1.2 km) elevation upwards. All observed samples from the explosions are pumicious and indicate that most - if not all- of the material involved in the eruptions was from new magma (i.e., not from the old dome). Both explosions produced in column collapses and resulting pyroclastic flows to the West of the volcano and reached Plymouth. Daytime access to Area B was suspended till further notice. After the second explosion at 07:07am, the level of activity dropped dramatically and there has been no signs of the old dome stability being compromised by the explosions. As a result, the NDPRAC reinstated daytime access to Area B from 02:00pm. The background level of activity has been very low for the rest of the week, suggesting either very low lava extrusion rate or non-energetic lava extrusion. On Tuesday 6, the very low level of activity observed by the MVO over the previous days allowed the NDPRAC to allow residents of Area B to overnight in their properties, with the understanding that people should be ready to leave the area at short notice if the activity was to resume and increase rapidly. MVO recorded 209 rockfalls, 45 long-period, 3 hybrids and 2 volcano-tectonic events in the past week. The majority of these events occurred between Friday 2 noon and Saturday 3 in the morning and seismic activity has been very low for the rest of the week. The average sulphur dioxide (SO2) flux was 811 tons per day with a minimum of 623 and a maximum of 1102. These values are slightly higher than those from the previous week. The Hazard Level is 4. Access to Area B has been restricted by the NDPRAC to residents only, except on the northern side of the Belham river where access is free to all. Additional information on the Soufrière Hills Volcano and the Hazard Level System can be found at the MVO website: http://www.mvo.ms. ============================================================== To unsubscribe from the volcano list, send the message: signoff volcano to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx To contribute to the volcano list, send your message to: volcano@xxxxxxxx Please do not send attachments. ==============================================================
