Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 7 December
to 6 pm 8 December 1997

Seismicity has increased very slightly today, with rockfall signals still predominant. Visibility has been excellent and further good views of the dome were obtained.

Between 16:00 yesterday and 16:00 today, the broadband seismic network recorded 132 rockfall signals, 45 long period and 10 hybrid earthquakes. This activity is consistent with continued dome growth in line with recent days.

Visibility was good today, and further views of the dome were obtained from a dome survey helicopter flight this afternoon. Theodolite observations were also made from Jack Boy Hill and Old Towne. The active growth is still concentrated high up on the Galways sector of the dome, but continuing rockfalls from the western side of the talus slope are cutting into the side of Chances Peak from above. Small rockfalls over the shoulder of the old dome, into the southern side of Tar River valley also appear to have taken place. Diffuse ash clouds have been produced throughout the day from these rockfalls. The wind direction today was in the more usual west-northwest quadrant, so onland ashfall was minimal. However, measurements of the average dust levels over the last 24 hours in Salem were slightly elevated as a result of old deposited ash drying out after recent wet weather.

The data from the recent EDM, GPS and dome surveys are being processed.

Although activity is still mainly focused on the southern side of the volcano, past experience has shown that the area of growth on the dome can change very quickly. Growth activity appears now to be backing up behind the major build-up of material in Galways, and rockfalls or pyroclastic flows starting to occur down Gages or Tar River in the near future would not be a surprise.

Montserrat Volcano Observatory