Montserrat Volcano Observatory

Morning Report
Report for the period 4 pm 11 August
to 7 am 12 August 1997

Activity at the volcano has remained at a high level with more hybrid earthquake swarms. The number of rockfalls has continued to rise.

Two hybrid swarms occurred overnight. The first, between 06:52 pm and 11:50 pm, was especially intense and included some of the highest amplitude hybrid earthquakes to be recorded so far. The second started at 05:39 am and is continuing at time of writing. Rockfall activity increased during the night with approximately 20 events being recorded between the two hybrid swarms.

No clear view of the dome was obtained during the night and early morning.

Hybrid earthquake swarms have continued which are assumed to be associated with rapid extrusion of new dome material. The small explosion yesterday demonstrates that further explosions may take place with little or no warning. Future explosions may be more intense and longer lasting 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 as strong a roof as possible. After an explosion small rocks and ash can be expected to fall everywhere on the island. Ash and falling rocks make driving hazardous. Ash is present in the atmosphere and masks should be worn outdoors.

Further pyroclastic flows are expected on all flanks of the volcano, and so at no time is it safe to enter the exclusion zone, including the Belham river valley. Access to the exclusion zone is completely restricted. The central zone is evacuated over night and people should not return to their homes until advised to do so. Everyone should remain vigilant and continue to listen to Radio Montserrat for any announcements.

Montserrat Volcano Observatory