Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 24 August
to 4 pm 25 August 1997

Activity at the volcano continues at a similar level to the previous 24 hours. Seismicity has again been dominated by rockfall and pyroclastic flow signals. Over the last 24 hours 25 hybrid earthquakes, 2 long period earthquakes, 3 VT earthquakes and 39 rockfalls triggered the broadband seismic network. The underlying pattern of approximately 12 hour cycles of enhanced activity are still detectable.

Activity peaked at around 8 am this morning after a slow build up starting at around 3:40 am. The peak of activity was marked by a series of pyroclastic flows in the Gages Valley and Mosquito Ghaut producing ash clouds which rose to approximately 7000 feet (2100 metres) above sea level. The majority of the flows were in Gages Valley, reaching as far west as St. George's Hill and as far north as Glen Mohr. Material is now beginning to build up around the northern side of St George's Hill and this may become a potential pathway into the Belham Valley for future pyroclastic flows. Activity decreased after 9 am. The remainder of the day has seen small rockfalls and further small pyroclastic flows in the upper Gages Valley. The large mass of dome which was reported above the Gages Wall a few days ago is now breaking up and it is likely that there will be further activity of this nature in the coming days.

A survey of the sea bed around the Tar River fan has been carried out today. The data are currently being processed and results will be presented in a future report. MVO would like to thanks the members of the Royal Montserrat Police Force and the crew members from HMS Liverpool for making this work possible.

Collapse of material from the dome may lead to further explosions and these may be more intense and longer lived than those already experienced. Explosions are also possible without much precursory activity as seen in early August. 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. The enhanced pyroclastic flow activity indicates increasingly instability of the dome and further pyroclastic flow activity is anticipated. This makes all of the exclusion zone extremely dangerous. Material accumulating against St. George's Hill may now make it possible for pyroclastic flows to reach into the Belham river valley from the Gages Valley as well as from the upper part of Mosquito Ghaut. Access to the exclusion zone is completely restricted, and people should stay away from the flanks of the volcano. People should remain vigilant and continue to listen to Radio Montserrat for any announcements.

Montserrat Volcano Observatory