Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 20 April
to 16:00 21 April 1997
The current alert level is ORANGE

The level of volcanic activity has remained low. Rockfall and pyroclastic flow activity has continued. These events were of a small to moderate size and are inferred to have occurred from the active area of the dome above the Galway's Wall.

The broadband network has detected 3 volcano-tectonic earthquakes, 7 long-period earthquakes and 31 rockfall/small pyroclastic flow signals. No hybrid earthquakes were detected. These numbers of events are similar to those detected yesterday. A teleseismic signal was also recorded at 8:22 am. MVO is awaiting further data from the Seismic Research Unit in Trinidad to better establish the location of this event.

The visibility has been excellent today, and observations of the dome were made during a helicopter flight this morning. The curved upper surface of the new extrusion has broken up, and the summit region is now dominated by a new curved face to the north of the extrusion. Theodolite measurements made from the observatory this morning showed that the height of the new extrusion is now 1000 m or 3280 feet. This is the highest that the dome has ever been. More material is being extruded to the west of the new dome so that the moat between the pre-September scar and the Easter scar is now filling up. Some ash and steam venting was seen from the summit area.

The alert level remains at ORANGE, because of the unstable dome above the Galway's Wall. Further collapses of the south side of the dome are expected and an escalation of the activity to more serious levels is always possible. Pyroclastic flows could occur without warning in both the Tar River and White River valleys, which makes these areas extremely dangerous. People are reminded to use ash masks when necessary and to listen to radio Montserrat for updates during periods of high activity

Montserrat Volcano Observatory