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Last Updated: Mar 5th, 2008 - 14:01:15 |
Montserrat Volcano Observatory
Report for the period 22 February to 29 February, 2008
Observations of the Soufrière Hills Volcano dome have been restricted once more this reporting period and poor visibility prevented views of the upper dome. The limited views made by MVO staff members during an observation flight on the morning of 29 February indicate that small rockfalls which spall from the exposed dome interior and talus flank above the Tar River Valley continue. These events plus rain assisted lahar (mudflow) contribute to the ongoing residual activity and the slow degrading of the eastern sector of the dome. The remaining areas of the dome may be considered of similar morphology to previous reporting periods due to the absence of rockfall in these areas, but it must be remembered that without good upper dome observations the exact structure of the dome cannot be stated for certain.
The seismic network was triggered by 4 hybrid earthquakes which all occurred during the early morning of 29 February.
The recorded sulphur dioxide (SO2) flux rate for the reporting period ranged from a maximum of 1485 tonnes per day (t/d) on 22 February to a minimum of 761 t/d on 24 February. The average flux rate for the period was 972 t/d. Following a slight decrease in flux levels over the previous reporting period the weekly average has increase once more.
A successful excursion with the Fourier Transform Infra Red (FTIR) monitor on 28 February resulted in a recorded HCl:SO2 ratio of 0.35.
Visible fumarolic activity in areas not shrouded by cloud indicate that they are no less active. Reported volcanic gas levels would support this. Steam fumaroles continue to be active around much of the dome and are an excellent guide to the apparent location of the old crater rim in places where it has been "overtopped" by the present dome.
The pause in dome growth continues but a possibility of collapse or explosion remains, however as the system cools without the introduction of fresh magma and the pause continues the likelihood of this is believed to decrease.
It must be remembered the potential hazard from lahar (mudflow) in the drainage channels around the volcano remains.
The alert level remained at 4.
Access to all areas south of the Belham Valley east of the Belham Bridge and areas further south including the south of Garibaldi Hill are prohibited as is south of Jackboy Hill to Bramble Airport and beyond. The Maritime Exclusion Zone around of the southern part of the island extends 4 km offshore from Spanish Point to Roches Bluff on the eastern side of the volcano and 2 km offshore from Ogarra's to Sturge Park on the southwest (readers are asked to refer to the risk map).
For further explanations of the volcanic phenomena described, 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
Director
Montserrat Volcano Observatory
Flemmings
Salem
Montserrat
Tel: 1 664 491 5647
FAX: 1-664-491-2423
e-mail: mick@mvo.ms; mhst@bgs.ac.uk
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| MVO report for the period May 2 to May 9, 2008 |
| MVO report for the period February 22 to February 29, 2008 |
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