Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 18 March
to 16:00 19 March 1997
The current alert level is AMBER

Activity at the volcano continued at a similar level to yesterday. An earthquake swarm started at 8:30 am this morning and it still continuing. Good views of the dome were obtained from the east and from the helicopter and indicate that the dome is still growing.

The seismicity today was dominated by an earthquake swarm which began this morning at 8:30 am and is still continuing. Since 4:00 pm yesterday, 56 hybrid earthquakes and 18 volcano-tectonic earthquakes have been recorded, most of which have occurred during the swarm. However, the swarm is not as intense as other, most recent swarms. All of these earthquakes were located at shallow depths beneath the crater. 9 rockfall signals were recorded by the network today, which is about the same number as yesterday. Low amplitude tremor on the Gages station was present between 2:30 pm and 3:30 pm this afternoon. No long period events have been recorded today.

Observations from the helicopter, from Whites and from O'Garro's today indicated that the dome is still extremely active. The main activity of the dome appears to be on its southern and eastern faces, with some moderate pyroclastic flows travelling down the southern side of the Tar River. Many small rockfalls appear to be channelled down a chute in the eastern face of the dome. On the north face of the dome, there is relatively little activity. Most of the recent growth of the dome is in the summit area of the dome with the appearance of several new stubby spines, and newly erupted material is now being extruded over lava of the October dome. Once again, there have several small pyroclastic flows over the Galway's Wall associated directly with large hybrid earthquake signals; there are also many small landslides that continue to erode the wall. Most of the pyroclastic flows have travelled down an erosive central chute on the wall.

A partial survey of the dome was carried out today from the helicopter, and static photographs were also taken at points around the volcano to add further information to the volume calculation. Results from this calculation will be released in a later report.

During the last few days the eastern slope of the dome continues to be unstable. Given that the dome is now large and continuing to grow, albeit slowly at the moment, a large collapse and pyroclastic flows could happen with little warning. The increase in activity from the Galway's Wall makes this area particularly hazardous. It is dangerous to spend the night in evacuated areas, because the situation could worsen rapidly over a period of a few hours. People entering Zone C are reminded to remain alert at all times, and spend the minimum possible time in the evacuated zone. The Tar River Valley and the upper Galway's area are very dangerous and should not be entered at any time.

Montserrat Volcano Observatory