Montserrat Volcano Observatory

Daily Report

Report for the period 16:00 01 October
to 16:00 02 October 1996

Activity at the Soufriere Hills volcano has remained at a relatively low level today, with only a few earthquakes recorded. Viewing conditions have been excellent and allowed observation of further dome growth within the scar caused by the 17/18 September explosion. Some small rock falls were seen from this new dome, and it has grown substantially since yesterday.

The seismic activity has remained at a low level, and was similar to the activity of the last two days There were 16 volcano-tectonic and no hybrid earthquakes. Most of the VTs occurred during a small swarm consisting of 13 earthquakes which occurred between 17:13 and 17:33 yesterday. They were all located at about 3 km depth beneath the crater. Twelve small rockfalls were also recorded during the period, and resulted in several small ash clouds. The rockfalls were slightly larger than those recorded recently.

Visibility was very good yesterday afternoon and evening, and again today from mid-morning. During a helicopter flight last night glowing was seen from the new dome and the scar caused by the 17/18 September explosion. Inspections this morning showed that the new dome had grown substantially overnight, and small rockfalls were seen from this dome for the first time. The new dome is now approximately twice the size it was yesterday and consist of a roughly oval, flat topped, light grey mass of rock with a dark grey interior.

EDM measurements were made at the southern triangle, between Chances Peak, Galway's and O'garros. The results will be processed tonight. The EDM reflector at Castle Peak was replaced this afternoon, as the original reflector, which was installed last October, had melted during the 17/18 September explosion. A new reflector was installed at the same site, and measurements to it were obtained successfully.

Further investigation of the pyroclastic flow deposits in the Tar River area continued today and a temperature of 330oC at about 70cm was obtained along the road from the Tar River estate house.

Further measurements of the entire dome complex were made this afternoon from the helicopter using the GPS equipment and laser-ranging binoculars. This technique allows an accurate map of the dome to be constructed, which helps in calculating the dome volume and rate of lava production. Surveys were also undertaken of the Tar River valley.

Two sites of the new seismic network were prepared at Galloways and St Georges Hill. This involved digging holes and laying a concrete base for the seismic instruments. A further six sites will be completed during the next few days.

MVO scientists expect that further rockfalls and possibly pyroclastic flows will occur during the next few days as the new 1 October dome grows. 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.

Montserrat Volcano Observatory