Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 13 August
to 4 pm 14 August 1997

Activity at the volcano has remained at a high level and following the pattern of the last few days is still dominated by hybrid earthquake swarms and dome growth.

591 hybrid earthquakes, 24 rockfalls and 1 long period earthquake triggered on the broadband seismic network over the last 24 hours. No volcano-tectonic earthquakes were recorded. The hybrids occurred in two swarms. The hybrid swarm which began at 1830 12/8/97 finally stopped at 0030 last night and contained 864 discrete events. The second swarm began at 0924, ended at 1623 and contained 244 events.

The recent hybrid earthquake swarms are thought to be associated with extrusion of new dome material. The high levels of activity suggest that extrusion rates are rapid. This is supported by visual observations of the dome yesterday morning which indicated that a large spine has been extruded in the crater area. Further brief views this morning showed that there is a new cluster of spines above the Gages wall area.

At 0538 a pyroclastic flow down the Gages valley was observed from the MVO. This was estimated to have reached the lower soufriere area. Further small pyroclastic flows occurred at 0930 and 1545 A very steep chute has formed at the top of the Gages valley and given the new growth of material on the dome, more pyroclastic flows in this area are probable.

Currently ongoing monitoring operations include further volume surveys to estimate the volume of deposits on the flanks of the volcano. Ash sampling in the north of the island is also being undertaken.

The small explosions which occurred on Monday and Tuesday demonstrate the potential for explosive eruptions. Further explosions are possible and these may be more intense and longer lived than those already experienced. If explosions do occur, the central zone should be evacuated immediately, and people in the northern zone should seek shelter under a strong roof as soon as possible. After an explosive event, small rocks and ash can be expected to fall anywhere on the island. Ash and falling rocks can make driving hazardous. Ash is present in the atmosphere and dust masks should be worn outdoors.

All ghauts on the volcano are now filled with hot pyroclastic flow deposits. It is expected that as the current elevated level of activity continues, further pyroclastic flows could occur on all flanks of the volcano. This makes all of the exclusion zone extremely dangerous. Pyroclastic flows could reach into the Belham river valley. Access to the exclusion zone is completely restricted, and people should stay away from the flanks of the volcano. The central zone is evacuated overnight and people should not return to their homes until advised to do so. People should remain vigilant and continue to listen to Radio Montserrat for any announcements.

Montserrat Volcano Observatory