Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 29 June
to 16:00 30 June 1996

Activity at the Soufriere Hills Volcano has been at about the same level today as during the previous twenty-four hours. Small and moderate-sized rockfalls from the lava dome still dominate activity.

The rockfall activity is at very similar levels to yesterday. The largest rockfall event occurred at 01:57 am on 30 June. This event had a duration of about two minutes and saturated the records of the closest seismic stations. Three other rockfall signals had durations in excess of a minute; these occurred at 07:40, 09:05 and 14:45 on 30 June. The number of long period and hybrid earthquakes remained low, and a very small volcano-tectonic earthquake occurred at 21:35 on 29 June. Broadband tremor was consistently low throughout this reporting period.

Visibility was good during the day, with observations made from the ground and helicopter during the afternoon of 30 June. Fixed photographs were taken from White's, Harris and Windy Hill which will enable a revised estimate of dome volume to be made over the next few days. It was observed that although rock falls are relatively rare, dome growth continues in a number of areas, most rapidly on the southern flank of the new dome, where considerable new material has been deposited in the upper part of the south fork of the Tar River. Little new material has fallen into the upper part of Fort Ghaut although it has a free path over Gages Wall; this suggests very little rockfall activity in this sector at present. Steam production was concentrated in the western moat.

Detailed measurements of the SO2 level in the volcanic plume were carried out today using a vehicle-mounted COSPEC instrument. The all-day programme started at 06:00 on 30 June and will continue until dusk - it is hoped that the various factors which might influence the gas production of the volcano during the day can be better constrained by today's measurements.

EDM measurements were taken on the eastern triangle to the newly-restored Castle Peak reflector today. The data showed no movement of the reflector since yesterday outside of the error of the technique. The University of Puerto Rico GPS survey continues, with measurements at Chances Peak, Tar River, Reid's Hill and St Georges Hill stations. Results continue to show only very small changes in line lengths across the volcano.

Glenn Thomson from Leeds University in the UK arrived on island today; he will be assisting with seismological work at MVO.

The Soufriere Hills Volcano is still considered to be highly dangerous to people and property on it's eastern and upper western flanks. Visits to the evacuated zone must be kept to an absolute minimum. The Tar River, Long Ground and Whites areas to the east and upper Fort Ghaut, Gages Village and Upper Amersham areas to the west are all extremely dangerous. All access roads remain closed and people should not enter these areas under any circumstances. If they do, they put themselves and others at direct risk of serious injury or death.

Montserrat Volcano Observatory