Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 26 March
to 16:00 27 March 1997
The current alert level is AMBER

The level of activity at the volcano over the last 24 hours has been slightly higher. A low intensity earthquake swarm occurred overnight, but rockfalls have continued and increased in number indicating that the dome complex continues to grow.

The seismic activity over the last 24 hours has been higher than over the last few days. Between 7:34 pm last night and 4:41 am this morning there was a hybrid and volcano-tectonic earthquake swarm. 31 hybrid earthquakes and 25 volcano-tectonic events were recorded during the 24 hour period, most of which occurred during the swarm. This swarm was less intense than other swarms over the last month and the events were also a lot smaller than the maximum sized events recorded recently. There have also been 14 long-period earthquakes and 35 rockfall signals triggering the seismic network; these are both increases on the numbers recorded yesterday.

Visual observations were made today during a sequence of helicopter flights, and from the ground at various points around the volcano. The southern face of the dome above Galway's Wall is extremely active with many rockfalls and small pyroclastic flows observed from this face. The south-west corner of the dome is dominated by a large tilted block approximately 20 metres across directly above Galway's Wall. Activity on this side has led to filling of the moat behind the scar left by the September 17th explosion, so that newly extruded dome material will soon move directly from the summit over the Galway's Wall. A few small pyroclastic flows and rockfalls, probably derived from pre-September dome material, were observed over Galway's Wall towards Galway's Soufriere.

A long-occupation GPS survey between Harris Lookout and Perches Mountain was completed today. The results have yet to be processed, but will be included in a future report.

EDM measurements were made on the western triangle today between Upper Amersham, Lower Amersham and Chances Steps. The results are currently being processed and will be available in a later report.

A full dome survey was completed today using the GPS technique. The results are currently being processed and should be available in a later report. Static photographs were also taken from fixed positions at Whites, Harris, Windy Hill and O'Garra's and will aid the volume calculation.

Fresh growth at the summit of the dome has been observed in the last few days. The dome is now very big, and a dome collapse with large pyroclastic flows could happen with little warning. 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