Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 4 December
to 16:00 5 December 1996
The current alert level is ORANGE

A revised volcanic risk map was released today to take account of the continued very dangerous situation at the volcano. All Montserratians are advised to make themselves aware of this new risk map and to stay vigilant.

The level of activity at the volcano has continued to increase today. The VT earthquake swarm has become more intense, and more rockfalls have occurred from the Galway's Wall. Two pyroclastic flows also occurred in the Tar River valley. A major collapse of the wall or the lava dome within the crater 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.

An inspection of the Galway's Wall was made from the helicopter this morning although visibility was generally poor. Avalanches had occurred overnight from the wall and from the southern end of Chance's Peak. A total of 9 signals associated with rock avalanches from the Galway's Wall were recorded during the reporting period.

The dome has not changed much in the last 24 hours, although small collapses from the active northeastern face of the October 1 dome this morning produced pyroclastic flows in the upper part of the Tar River valley; a total of 3 dome rockfall signals were recorded during today. Further signs of instability of the dome are expected while the VT swarm continues to shake the upper part of the volcano.

The VT earthquake swarm which started on 30 November has continued, and intensified slightly. 337 VT events were recorded today, an increase from yesterday. The current swarm is the most intensive recorded since the start of the eruption in July 1995. The largest earthquakes today were not significantly larger than those of yesterday, although reports have been received of these earthquakes being felt in the Weekes' area.

No EDM measurements were made today due to very low cloud over the volcano. Efforts to install new monitoring equipment on Chance's Peak and attempts to make measurements to the new reflectors on the Galway's Wall have not been made over the past two days due to the high level of danger involved. The eastern network of GPS points was occupied today; the results are being processed at the moment.

Scientists continue to attempt to model possible tsunami hazards should a major avalanche of the Galway's Wall reach the sea. Initial indications are that a wave a few metres high may run along the southwest coast of Montserrat.

Montserrat Volcano Observatory