Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 26 August
to 4 pm 27 August 1997

Activity at the volcano has declined slightly compared to the previous 24 hours. The regular cycles of seismic activity seen over recent weeks appear to have stopped. Rockfall activity occurred throughout the reporting period at a fairly low level. Over the last 24 hours 8 hybrid earthquakes, 3 long period earthquakes, 11 VT earthquakes and 63 rockfalls triggered the broadband seismic network.

The VT earthquakes were all small, and no accurate locations could be determined for them.

Only a few partial views of the dome were possible today. There was semi-continuous steam venting from the dome, but little ash production. Rockfall and fumarolic activity was observed on the south-east flank of the dome, an area that has not been very active recently, with some of the rockfalls travelling into the southern part of the Tar River Valley. Some incandescence was seen from the observatory last night.

Ground deformation measurements were carried out today to determine whether there has been any recent deformation of the volcano. GPS measurements were taken at Harris, White's, Long Ground and O'Garras. Distance measurements were made using the total station from the observatory to Lee's. The data is still being processed.

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 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 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