Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 03 April
to 16:00 04 April 1997
The current alert level is ORANGE

The level of volcanic activity has been fairly low today, although there was a swarm of volcano-tectonic and hybrid earthquakes overnight. Some of the earthquakes were deeper than the seismicity recorded recently. The level of rockfalls was about the same as yesterday, with two pyroclastic flows in the White River valley this morning.

A total of 54 volcano-tectonic, 60 hybrid and 12 long-period earthquakes were recorded during the period. The earthquake swarm began at 5:10 pm, and lasted until 4:53 am, although there were few earthquakes after 2:00 am. The swarm consisted of volcano-tectonic earthquakes, most of which were located at depths of around 3 km, and shallower hybrid earthquakes. Five of the shallow earthquakes were comparable in size to the largest earthquakes recorded yesterday, and would probably have been felt close to the volcano. The swarm was very similar to the earthquake swarm recorded on 1-2 November 1996, although last night's swarm had larger earthquakes.

Since the end of the swarm the level of activity has been low, although there has been a resumption of rockfall and pyroclastic flow activity, with 27 signals recorded by the seismic network. Two pyroclastic flows this morning resulted in ash clouds that were blown to the south-west.

Between 11:10 pm and 1 am there were flash floods to the south-west of the volcano that were strongly recorded by many of the seismic stations. This morning, new flash flood deposits were seen in Fort Ghaut and Aymer's Ghaut.

The volcano has been cloudy for most of the day, so good views of the crater area were not possible today. A brief trip was made to the Tar River valley to collect rock samples from the recent pyroclastic flow.

COSPEC measurements were made today along the road to the south-west of the island. The volcanic plume was being blown to the south, and so the complete plume could not be sampled. The results have not yet been processed.

The volcanic activity has changed in nature in the last 24 hours, and further pyroclastic flows and earthquake swarms are expected. Nobody should sleep in zones A to D tonight, which includes Plymouth, St Patrick's, the central corridor, Harris', Long Ground, Spanish Point and Richmond Hill. Zone E, which includes Corkhill and the airport, remains safe at this time.

Montserrat Volcano Observatory