Montserrat Volcano Observatory

Daily Report
Report for the period 16.00 20 May
to 16:00 21 May 1997
The current alert level is ORANGE

Volcanic activity has remained at an elevated level during the last 24 hours, although a slightly lower than the previous days. There have been more hybrid earthquakes, and small pyroclastic flows from the north of the dome.

The volcano has been cloudy for most of the day, but occasional clear spells have allowed brief views of the lower slopes of the dome. A possible new spine was sighted on the northern side of the dome, close to the top of Mosquito Ghaut. There were pyroclastic flows yesterday evening on the north side of the dome. These flows occurred after the end of yesterday's earthquake swarm, and were smaller that the flows on previous days.

A total of 157 hybrid and 4 long-period earthquakes were recorded in the last 24 hours, which is a decrease in numbers since yesterday. There were also 40 rockfall signals recorded. The hybrid earthquakes were in two swarms, the first of which ended at 6:14 pm yesterday. The second swarm began at 8:02 am, and was still ongoing at the end of the reporting period.

The tiltmeter installed a few days ago in a hut on Chances Peak is showing movements that are synchronous with the hybrid earthquake swarms. The tiltmeter shows that the volcano swells slightly during the swarms, and then subsides again. This is thought to be related to an increase in magma pressure at a shallow level during the swarms.

A GPS survey was carried out this morning on a network of points on the eastern side. This was designed to check a recent GPS measurement which suggested there had been movement of the site at Hermitage. The reading could not be replicated, and the measured position of the point was similar to previous measurements made in March and April.

The volcano is in a dangerous phase, with the possibility of pyroclastic flows into the northern ghauts and a further escalation in activity. Dome growth continues, and further pyroclastic flow activity is inevitable. The Tar River valley, Long Ground, White's and Tuitt's areas are very dangerous, and should not be entered because of the dangers of pyroclastic flows. Nobody should enter zones A and B, and only essential visits should be made to the evacuated zone. Ash masks should be worn when in the ashy areas.

Montserrat Volcano Observatory