MVO report for the period midday November 02 to midday November 09, 2007
By MVO
Fri, 9 Nov 2007, 09:23
Montserrat Volcano Observatory
Report for the period 02 November to 09 November 2007
Measurable activity at the Soufrière Hills Volcano has remained low with no significant change throughout the period and the pause in lava extrusion [and dome growth] continues. Visual observations showed that fumarolic activity was concentrated on the northern and southern flanks of the dome. The vent formerly described as located behind Gages Wall remains active, and appears to tap deeper, hotter regions of the dome than other fumaroles, emitting bluish sulphur dioxide gas. Two prominent channels were also observed on the eastern flank of the dome below this vent, and there appears to have been some erosion in the region of the Gages Wall.
Whilst lava extrusion has ceased and the dome may not be actively growing, it remains as a large mass of partially molten lava capable of collapsing or exploding although the likelihood of this is thought to decrease with time as no further lava extrusion occurs. During heavy downpours, such during the passing of tropical depressions, lahar activity in drainages around the volcano (including the Belham Valley to the northwest), remains a potential hazard.
Recorded seismic activity remained low throughout the period, and the seismic network recorded 16 rockfall signals and 12 volcano-tectonic earthquakes. Almost all of the volcano-tectonic earthquake occurred within a small swarm, early on 08 November.
The recorded sulphur dioxide (SO2) flux rate for the period was variable, ranging from a maximum of a 862 tonnes per day (t/d) to a minimum of to 259 t/d. This gave average flux rate for the period of 596 t/d, close to the long-term average for the eruption, which remains at around 550 t/d.
FTIR measurements on 05 and 08 November yielded HCl:SO2 ratios of 0.31 and 0.36 respectively, remaining in line with recent measurements and past periods of residual activity (pauses in lava extrusion).
The alert level remained at 4.
Residents of Montserrat and visitors to the island are advised to tune into ZJB Radio 88.3 or 95.5 FM for up-to-date information on the volcano.
Access to all areas on the southern flanks of the Belham Valley east of the Belham Bridge and areas south are prohibited as is south of Jack Boy Hill to Bramble airport and beyond. The maritime exclusion zone around the southern part of the island extends 4 km off shore from Spanish Point to Roches Yard on the east side of the volcano, 2 km offshore from O’Garras to Sturge Park on the south-west (readers are referred to the updated risk map, available on the MVO website).
Additionally for further explanations of the volcanic phenomena described, and information about the Soufrière Hills Volcano and the ongoing eruption, please look at the MVO website: http://www.mvo.ms.
Vicky Hards
Director
Montserrat Volcano Observatory
P.O. BOX 318
Flemmings
Montserrat
West Indies
Tel: 1-664-491-5647
FAX: 1-664-491-2423
Email: vicky@mvo.ms