Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 6 December
to 16:00 7 December 1996
The current alert level is ORANGE

The level of seismic activity has increased slightly during the last 24 hours and the number and size of the largest earthquakes remains the same. The Galway's Wall has become more unstable and there were a number of sizeable rock avalanches during the reporting period. A major collapse of the wall could expose hot, gas-rich magma from the lower sections of the dome, and trigger a lateral blast. This blast could occur in a number of directions from the crater and affect a large part of southern Montserrat. There is also a small possibility that a vertical eruption column could be generated during any heightened activity. All residents of Montserrat are urged to follow the alert procedures at this time of greatly heightened anxiety over the volcanic situation.

A total of 201 volcano-tectonic earthquakes have been recorded, a slight increase in numbers since yesterday. The maximum magnitude of the earthquakes has remained about the same; this magnitude is estimated to be around 3 on the Richter Scale. Several earthquakes were felt at the observation post overlooking the Galway's Wall during the day. There were eight landslides from the Galway's Wall that were large enough to be detected by the seismic network, five within a short period yesterday evening. Three dome rockfalls were also recorded. The Gages seismometer has been showing semi-continuous, low-amplitude tremor for much of the reporting period.

Several helicopter inspections of the Galway's Wall were made during the day, although visibility was not very good. The landslides overnight deposited very large chunks of rock at the base of the wall - some of these chunks are estimated to be 20 ft across. Glimpses of the top of the wall indicated that it has partially fallen down in the central section. Several earthquakes shook the wall during observations, causing minor rock avalanches. The maximum runout of debris so far is 600 metres from the wall. Some small cracks have been noted in the lower part of the wall.

The crater area was not visible today because of low cloud, which also prevented any EDM measurements from being made.

A GPS survey of the volcano-wide network was undertaken today - the field teams are just now returning to the observatory.

Chandradath Ramsingh arrived today from SRU in Trinidad to assist in the electronics department at MVO. Also, Jean-Christophe Komorowski returned to Montserrat from Guadeloupe today - he will be staying 10 days or so to assist with MVO operations and to provide a link with authorities and the volcano observatory in Guadeloupe.

Montserrat Volcano Observatory