Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 27 August
to 4 pm 28 August 1997

Activity at the volcano has increased slightly with a period of enhanced rockfall activity around noon today, similar to the regular cycles of rockfall activity seen a few days ago. Otherwise, seismic activity was low, although there was an above-average number of LP earthquakes. Over the last 24 hours 2 hybrid earthquakes, 24 long-period earthquakes, 7 VT earthquakes and 54 rockfalls triggered the broadband seismic network.

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

Visibility was excellent for much of the day. Observations of the dome showed some significant changes. The new dome is high and very steep above Gages, and has a summit spine. Much of the rockfall activity appears to be from the new dome, which has not yet totally filled the crater formed by the explosions of early August. Unless there is a change in the focus of activity, this dome is likely to collapse and generate pyroclastic flows into the Gages valley. The pre-August dome above Galways is now very steep and also has potential for collapse.

The dome was surveyed today to estimate the size of the dome and its rate of growth. Photographs were taken from fixed locations around the volcano and the locations of points on the dome were surveyed from the helicopter using laser-ranging binoculars. 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 previous explosions. Explosions are also possible without much warning - as happened in early August. If an explosion does occur, small rocks and ash can fall anywhere on the island. The central zone should be evacuated immediately, and people in the northern zone should seek shelter under a strong roof as soon as possible. Helmets or other head protection should be used and dust masks should be worn outdoors. Ash and falling rocks can make driving hazardous.

Further pyroclastic flow activity is anticipated, possibly without any warning. All ghauts on the volcano are now filled with hot pyroclastic flow deposits and this makes all of the exclusion zone extremely dangerous because the flows will not be confined by the ghauts. Material accumulating behind St. George's Hill may now make it possible for pyroclastic flows to travel 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.

Montserrat Volcano Observatory