Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 11 February
to 16:00 12 February 1997
The current alert level is ORANGE

Volcanic activity has continued at a low level, although slightly increased from yesterday. Another swarm of earthquakes occurred overnight, followed by a short episode of tremor. There were a few pyroclastic flows, the largest of which reached onto the fan at the bottom of the Tar River valley.

The earthquake swarm consisted of 111 volcano-tectonic and 29 hybrid earthquakes, and lasted from 21:40 pm to 7:30 am. This is larger than the recent swarms. The swarm was followed by an episode of tremor from 7:30 am to 8:50 am. This tremor episode was the first one since 7 February, and was shorter and smaller than most of the previous episodes. Following the tremor, the seismic activity was at a low level, with a few pyroclastic flows and rockfalls.

Visual observations today were restricted by low cloud. Some views of the dome were possible, and there do not seem to have been many changes since yesterday. There were a few pyroclastic flows, the largest of which was a moderate flow at 9:15 am. This flow reached onto the fan, and produced an ash cloud that blew over Plymouth, with some light ash also falling in Corkhill.

Gravity measurements were made today at Whites and Hermitage.

Despite the low level of activity, more pyroclastic flows are expected from the steep eastern face of the dome. Any collapses are likely to be gradual, and produce small or moderate pyroclastic flows. However, a larger and more prolonged collapse can not be ruled out. Residents are reminded to remain alert and responsible at all times, carry ash masks and spend the minimum possible time in the evacuated zone. Zone E, which includes Cork Hill and the airport, remains safe at this time. The Tar River Valley and the upper Galway's area are very dangerous.

Montserrat Volcano Observatory