Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 16 December
to 6 pm 17 December 1997

The volcanic activity remains at a relatively low level, with rockfall signals being the dominant seismic activity recorded on the seismograph network. However, there were more hybrid signals recorded today than on recent days.

Between 16:00 yesterday and 12:10 today, the broadband seismic network recorded 96 rockfall signals, 20 long period events, 46 hybrid earthquakes, and one volcano-tectonic earthquake. Three of the long-period events and one of the hybrid events were accompanied by rockfall signals. The broadband seismic system today ceased to work at 12:10, and thus today's count is incomplete. Work is ongoing to try to rectify the situation. The short period network is still in action.

The mountain was covered in thick cloud this morning, but then cleared markedly, so clear views of the dome were possible. Near continuous rock fall activity was observed from the top of the dome above the Galways growth area. The south part of the Galways dome face, near Galway's Mountain appeared to be oversteepened, but the most active area was close to Chances Peak. Further theodolite points of positions on the dome were obtained from the South Soufriere Hills observation post and a site close to the White River. The highest point on the dome visible from these places was at a height of 972 m or about 3200 feet.

The GPS survey of the Lee's Yard network from yesterday showed that there is no clear trend in the movement of the points on the network.

Dust levels in St. Johns, Woodlands and St. Peters remain low.

Although activity is still subdued and mainly focused in the southern central part of the volcano, 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 a renewal of rockfalls or pyroclastic flows down Gages or Tar River would not be a surprise in the near future.

Yesterday evening, Lutchman Pollard of the Seismic Research Unit in Trinidad and Jenni Barclay of the University of California at Berkeley both arrived for tours of duty at the observatory.

Montserrat Volcano Observatory