MVO report for the period midday 31 August to midday 7th September, 2007
By MVO
Fri, 7 Sep 2007, 16:12
Montserrat Volcano Observatory
Report for the period midday 31 August to midday 7 September 2007
Activity during the reporting period for the Soufrière Hills Volcano (SHV) continued to be low. Partial dome visibility on 5 September revealed no changes in morphology. 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 decreases with time as no further lava extrusion occurs. The amount of material above Tyres Ghaut to the NW is sufficient to generate pyroclastic flows and surges capable of impacting on the lower Belham Valley and low lying surrounding areas including lower Happy Hill and the Old Towne ridge.
Measurable seismic activity remained very low with the seismic network recording 7 rockfalls, 1 volcano-tectonic earthquakes and one (1) long period event.
The sulphur dioxide (SO2) flux rate ranged from a maximum of 787 tonnes per day (t/d) to a minimum of 321 t/d during the reporting period. The average flux rate for the period stood at 575 t/d which is only slightly higher than the long-term average which remains around 550 t/d. A single Fourier Transform Infrared (FTIR) measurement of hydrogen chloride to sulphur dioxide ratio was possible on 5 September and was 0.43 very similar to other recent measurements and reflecting no dome growth.
Unfortunately due to access problems to South Soufrière Hill baseline calculations between GPS stations were not possible.
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 lower flanks of the Belham Valley and further south, and south of Jack Boy Hill to Bramble airport and beyond is prohibited at all times (readers are refereed to the updated risk map). 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, and 2 km offshore from Isles Bay to Old Road Bluff on the west (maritime risk map).
For further explanations of the volcanic phenomena described, and information about the Soufrière Hills Volcano and the ongoing eruption, please look at the rest of the MVO website. http://www.mvo.ms.
Mick Strutt
Acting Director
Montserrat Volcano Observatory
P.O. BOX 318
Flemmings
Montserrat
West Indies
Tel: 1-664-491-5647
FAX: 1-664-491-2423
Email: mick@mvo.ms / mhst@bgs.ac.uk