Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 24 September
to 16:00 25 September 1996

Activity at the Soufriere Hills volcano during this reporting period has continued at a low level. Small rockfalls continue to be the most dominant feature of the seismicity although a few hybrid events were recorded.

Eighty-one small rockfalls were recorded during the reporting period. The largest occurred at 21:43 on 24 September and 15:25 on 25 September. Twelve hybrid events were also recorded. A single mudflow signal which may be related to remobilisation of ash deposits in Fort Ghaut was recorded by the Gages seismic station between 06:34 and 07:33 on 24 September. Low amplitude broadband tremor of variable amplitude was recorded throughout the reporting period.

Visibility improved during the reporting period but no clear view were obtained of the new scar feature. A late afternoon flight in helicopter on 24 September afforded some brief views of the crater. There were no signs of any new material at the bottom of the scar apart from debris derived from rockfalls off the side walls of the scar. Abundant steaming and sulphur deposits were observed at the base of the scar feature. Low cloud cover for most of 25 September only allowed views of the lower flanks of the dome. Several unstable blocks are present on the northern and eastern flanks of the dome; these are expected to produce rockfalls during the next few days.

EDM measurements were conducted on the northern triangle to Farrells today. The data from this occupation is currently being processed. No GPS measurements were made by the MVO today. GPS stations operated by the University of Puerto Rico at Reids Hill, Hermitage and St Georges Hill were occupied today.

MVO scientists expect that rockfalls and possibly pyroclastic flows will occur during the next few days as the unstable sides of the new scar feature at English's Crater stabilise. All indications are that the rockfalls and pyroclastic flows will be confined to the Tar River valley area. Dust masks should be worn at all times in ashy environments, which may persist for some time as ash dries out and blows around. Drivers should exercise caution and consideration for other road users, especially when driving through areas still affected by ash or gravel.

The extensive damage which occurred in the Long Ground area last week demonstrates the extreme danger which individuals subject themselves to if they venture into this area or beyond into the Tar River valley. The Tar River and Long Ground areas are now extremely hazardous and we urge individuals who persist in ignoring this advice to think very seriously before making trips to these potentially deadly zones.

Dr Glen Mattioli and Ms Lorna Nieves of the University of Puerto Rico left the island today after a brief visit during which the University of Puerto Rico's GPS network located on the flanks of the volcano was reoccupied.

Montserrat Volcano Observatory