Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 17 February
to 16:00 18 February 1997
The current alert level is AMBER

Activity at the volcano has continued at a low level. There was one swarm of earthquakes that lasted for most of the day. Visibility has been excellent this afternoon, and a few small pyroclastic flows were observed.

The earthquake swarm comprised both volcano-tectonic and hybrid earthquakes, and lasted from 7:10 am to 2:50 pm, with a total of 56 VTs and 36 hybrids recorded. Most of the VTs occurred early in the swarm, before midday, and the hybrids appeared after that. There was a short episode of low-amplitude tremor at the same time as the hybrid earthquakes, which was detected only on the Long Ground seismic station.

An episode of volcanic tremor occurred between 6 pm and 6:40 pm last night. At the peak in the tremor, at least one small pyroclastic flow was generated, and an ash cloud drifted to the west. The largest pyroclastic flow travelled as far as the position of the old road across the Tar River valley.

Visibility was very good this afternoon, and excellent views were obtained from Whites and the helicopter. A few small pyroclastic flows and rockfalls were seen from the eastern face, and a few rockfalls went down the northern side of the dome towards Farrells.

Some more dome material has come over the Galway's Wall, but the rockfalls did not travel as far as previous ones. The top of the wall is still crumbling, and there are now three well-developed gullies that are channelling dome material.

Yesterday's measurement of the dome volume gave an extrusion rate of 4 cubic metres per second, which is similar to recent measurements.

The dome is currently larger than ever before, and so further dome collapses and pyroclastic flows are expected. These will probably follow the recent pattern, but a change in the activity could happen at any time. Visitors to zone C are reminded to remain alert and responsible at all times, carry ash masks and spend the minimum possible time in the evacuated zone. It is advisable to have access to a battery operated radio in case of electricity power cuts. Ash levels in Plymouth are hazardous, especially during dry, windy weather, and so it is essential to wear masks in areas affected by ash. Flash floods could cut off access to areas south of Fort Ghaut; visitors should leave that area when it rains. The Tar River Valley and the upper Galway's area are very dangerous.

Montserrat Volcano Observatory