Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 15 April
to 16:00 16 April 1997
The current alert level is ORANGE

The level of activity has been relatively low today, with only small pyroclastic flows generated from the unstable face of the dome. There was a short earthquake swarm overnight. Ash clouds generated from rockfalls and pyroclastic flows have been blown northwards by the wind.

The swarm of hybrid earthquakes overnight lasted from 4.57 am to 6.15 am and contained only 3 large events in the total of 15. This swarm was preceded by four small volcano-tectonic earthquakes, one of which was located at a depth of about 1.5 miles beneath the crater. A total of 7 long period events were also recorded and 17 rockfalls triggered the seismic system, one of which directly followed a long period event. A regional earthquake was recorded by the network late yesterday afternoon - it was located in the Venezuela area and had a magnitude of 6.2. Shaking from this earthquake was strongly felt on the island of Curacao.

Visual observations were made from various points on the ground today. Several moderate ash clouds were generated from the larger rockfalls during the day and these were blown to the north by the unusual southerly winds. Very light ashfall occurred in some areas but most of the ash was carried away from Montserrat in a plume which extended as far as Nevis. Rockfalls were generated only from the active face of the dome which currently sits above the Galway's Wall, and rockfalls descended into the upper parts of the White River valley.

The amount of steam and gas production from the dome has varied during the day, although the recent pattern of increased steaming in the early part of the afternoon was again noted.

A GPS survey of the eastern flanks of the volcano was undertaken today and the results are being processed at present.

The alert level remains at ORANGE, because of the unstable dome above the Galway's Wall. Further collapses of the south side of the dome are expected. While these collapses will probably not be much larger than recent collapses, an escalation of the activity to more serious levels is always possible. Pyroclastic flows could occur without warning in both the Tar River and White River valleys, and these and surrounding areas remain extremely dangerous. Visits to zone C should be kept brief. Zone D should not be occupied tonight.

Montserrat Volcano Observatory