Montserrat’s governor issues new statement on ongoing volcanic situation

Montserrat
Montserrat’s governor issues new statement on ongoing volcanic situation
By Government Information Unit, Montserrat
Fri, 9 Mar 2007, 17:00

H.E Governor Deborah Barnes Jones

Brades, Montserrat, March 9, 2007 (Government Information Unit) - This statement follows on from that made by the Governor on 6 March, when she said that the Scientific Advisory Committee (SAC) had produced a report about the risks to the community from the Soufriere Hills volcano.

The Governor was grateful for the opportunity to meet with the Emergency Policy Group (EPG) on 5 March, and the Volcano Executive Group (VEG) on 8 March to hear their views on the latest developments.

The MVO have been updating the community on a daily basis. There are no surprises in the analysis of the situation at the volcano in the SAC report. Risk to the area north of Nantes river remains at background levels. The north remains safe for community life.

What is new is the use the SAC have made of the available information. The report takes the most recent data on dome volumes and concentrates on an area of high risk but low probability. That is the matter of lateral blasts. A lateral blast is powerful explosions with a significant directed horizontal component which can generate high energy pyroclastic flows and surges. The civil authorities, working through the EPG and the VEG have been coming to terms with the implications of the SAC modelling in this area. The SAC have used cutting edge technology to give information on what might be expected to happen in the unlikely event of a lateral blast directed towards the north-west. This is an unlikely scenario, but cannot be ruled out. It will become more likely if dome growth returns to the north-west side of the volcano; not the case at present. The results of a lateral blast, should one take place, could be expected to be extremely harmful.

During discussion, the civil authorities looked at the following information included in the latest scientific advice:

• The threat posed to the NW sector by the volume of material which could flow down Tyers Ghaut and reach the lower Belham Valley and surrounding areas has not diminished.
• The range for the amount of material available above Tyers Ghaut is large, depending on what method of calculation is used, between 13 and 23 m cubic metres.
• The likely scenario for March is that the dome will continue building, with no collapse.
• The present unsafe area represents the minimum boundary to protect the community from the present risk, which comes primarily from a gravitational collapse.
• The chance of a lateral blast is “unlikely but possible”.

On the basis of the detailed information provided by the SAC, the conclusions discussed in VEG were that:

• The present boundaries of the unsafe area should remain in place.
• Daytime access to the unsafe area may continue for the time being, while the results for the trial prolongation of the daytime hours are considered by the RMPF. But there is risk to those entering the area, and they need to be briefed on the information now received.
• A public information effort should begin immediately to brief the wider community on the information now available.

• If the likelihood of lateral blast increases, or the amount of material above Tyres Ghaut makes a flow of over 20million cu metres of material into the Lower Belham a possibility, the authorities would need to take further measures, including relocation, to protect the population.

• Work should go forward now to understand better the likelihood of a lateral blast, what might cause it to increase, and how to advise the population to deal with this.
Source: http://www.giu.gov.ms/news/governor_issues_statement_on_sac_march0907.htm