Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 30 September
to 16:00 01 October 1996

Activity at the Soufriere Hills volcano has remained at a relatively low level today. Excellent visibility enabled the first sightings of new dome material in the base of the mid-September scar.

The seismic activity has remained at the lower level noted yesterday, with only 6 volcano-tectonic and 5 hybrid earthquakes recorded. The volcano-tectonic earthquakes were located slightly deeper than over the past few days, at 2 to 4 km (1.5 to 2.5 miles) beneath the crater. Seven small rockfalls were also recorded during the period. Two of the rockfalls today produced small ash clouds; these were timed at 09:25 and 15:46 but the clouds were not sufficiently large to produce any ashfall.

Visibility was very good in the later part of this afternoon, with excellent views obtained of the entire dome area. Positive confirmation of new dome growth in the base of the new scar was obtained; a light grey, blocky dome about 10 to 15 thousand cubic metres in volume has formed on the surface over the past two days, indicating a relatively slow growth rate compared to that prior to the collapse of 17/18 September. The full extent of the collapse scar was also seen for the first time and it was confirmed that about 25% of the dome collapsed on 17/18 September. Deposits from several new rockfalls and small pyroclastic flows were noted in the deep channel leading from the scar down the Tar River valley.

No EDM measurements were attempted today, although the reflector on Chance's Peak was re-oriented so that measurements on the southern triangle should again be possible.

Volume measurements were started late this afternoon for the entire dome; this helicopter technique uses very accurate on-board GPS equipment and laser binoculars which gives distances to certain points on the dome. The surface of the dome can thus be mapped and a volume estimate made. The results of these surveys take some time to compute so will not be available for several days.

Work continued on the installation of the computer and other equipment for the new seismic network. The network will consist of eight new seismic stations which will be installed during the next two weeks.

Further rockfalls and possibly pyroclastic flows will occur during the next few days as the new dome begins to grow bigger within the scar. Scientists expect that these will be confined to the Tar River valley area. There is still a lot of ash around, and dust masks should be worn if necessary.

Individuals put themselves in extreme danger if they venture beyond the Long Ground area into the Tar River valley. All individuals passing checkpoints in whatever part of the island are reminded that they are entering areas which may become unsafe very quickly, and everyone should be on maximum alert in all of these areas. All residents of Montserrat are asked to make themselves familiar with evacuation procedures and the new alert system which will be publicised over the next few weeks on the radio and in the newspaper.

Montserrat Volcano Observatory