Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 12 March
to 16:00 13 March 1997
The current alert level is AMBER

Activity at the volcano has been slightly higher than yesterday with the occurrence of another earthquake swarm. Several small pyroclastic flows travelled over Galway's Wall and a new spine, first seen on 11 March, is still growing noticeably.

Seismic activity at the volcano has been dominated by another volcano-tectonic and hybrid earthquake swarm that began yesterday afternoon and continued into the current reporting period. The activity peaked at approximately 8 pm last night and continued until 8.54 am this morning. A total of 98 hybrids and 35 volcano-tectonic events were recorded, most of which occurred during the swarm. In addition, 11 rockfalls and 1 long-period earthquake were recorded during the period. Low amplitude tremor was also recorded on the Gages seismic station for most of the reporting period, and the amplitude of the tremor is increasing slightly at the present time.

Good views of the dome from the eastern side of the volcano indicate that rockfall activity continues to be concentrated in a wide area extending from the south-eastern to the north-eastern part of the dome. The main active chute is currently in the region of the north side of the January scar. A new spine that was first observed on 11 March continues to grow and is estimated to be approximately 30 m high. The CCTV located at the observation post at Galway's has allowed good views of pyroclastic flow activity in this area. At least two small pyroclastic flows travelled a maximum of 1 km from Galway's Wall, and produced small ash clouds which drifted over Plymouth. Unlike yesterday, there seemed to be no direct correlation between volcano-tectonic earthquakes and rock avalanches from the Galway's wall.

The results obtained from the long occupation GPS survey between Harris and Hermitage yesterday indicate that the Hermitage site has increased in height and moved to the north-north-east since it was last measured on 18 January.

EDM measurements that were made yesterday on the radial lines between Upper and Lower Amersham and Lower Amersham and Chances Peak steps continue to show no major changes in the lengths of the lines.

During the last few days the eastern slope of the dome has become increasingly unstable. Given that the dome is now large and continuing to grow, a large collapse and pyroclastic flows could happen with little warning. The increase in activity from the Galway's Wall makes this area particularly hazardous. It is dangerous to spend the night in evacuated areas, because the situation could worsen rapidly over a period of a few hours. People entering Zone C are reminded to remain alert at all times, and spend the minimum possible time in the evacuated zone. The Tar River Valley and the upper Galway's area are very dangerous and should not be entered at any time.

Montserrat Volcano Observatory