Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 20 June
to 4 pm 21 June 1997
The current alert level is ORANGE

Volcanic activity continues at a moderate level, comprising mainly rockfalls from the growing dome.

There was another pulse of enhanced rockfall activity which started about 5 pm yesterday, and lasted until about midnight. Last night's pulse was moderate, producing some ash but there were no significant pyroclastic flows. Tremor was recorded on the Gages and Windy Hill seismometers for a time. A second, smaller pulse of activity started during mid-morning today and was declining at the end of the period under report. The time interval between the start of these recent pulses has lengthened to about 20 hours.

The MVO airport observers reported low cloud on the mountain throughout the day. Most of the activity occurred as rockfalls, concentrated mainly in the Tar River valley. A few rockfalls entered Tuitt's Ghaut. Some fairly large blocks came down from the top of the dome in these falls, but generally they did not appear to generate the same amount of convecting ash as in previous episodes.

An inspection of the lower parts of the dome and the upper ghauts from the helicopter this afternoon revealed that the chute above Mosquito Ghaut, formed in Tuesday night's pyroclastic flow, has now been almost completely refilled. During the flight there was a little rockfall activity above Mosquito Ghaut, but no activity observed above Gage's valley or Galways.

Rockfall signals dominated the seismic recordings again today. There were 188 rockfall signals, about average for the last few days. While the number of earthquakes remained low, there was a slight increase from yesterday: today's tally was nine hybrid earthquakes and thirteen long period earthquakes, but again no volcano-tectonic earthquakes.

Further COSPEC runs were being made this afternoon. EDM measurements were made to the new reflector at Farrell's today: these will repeated to establish the stability of the installation.

The level of activity has decreased in the last few days, but this is probably a lull period, and further pyroclastic flows and surges could travel into Gages valley, Mosquito Ghaut, Tuitt's Ghaut or the Tar River valley at any time. Access to Plymouth is restricted for the time being. Zones A and B, which include Tuitt's, Bramble, Bethel, Spanish Point, Farms, Harris and Trants, are extremely dangerous and nobody should go into this area at all.

Bramble Airport remains operational, but the public are reminded that it is open only for essential travel purposes.

Montserrat Volcano Observatory