Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 15 December
to 6 pm 16 December 1997

The volcanic activity remains at a relatively low level, with rockfall signals being the dominant seismic activity recorded on the seismograph network.

Between 16:00 yesterday and 16:00 today, the broadband seismic network recorded 44 rockfall signals, 47 long period events, 16 hybrid earthquakes, and 5 volcano-tectonic earthquakes. Twenty of the long-period events were accompanied by rockfall signals. This activity is consistent with steady continuing dome growth.

The mountain has remained obscured by cloud most of today so clear views of the dome have not been possible. A steady plume of steam and ash continues to emanate from the top of the dome above the Galways growth area, with occasional clouds of ash rising from the rockfalls. One larger cloud of ash was produced at about 4:50pm today which mixed with a dark rain cloud to give the appearance of a large eruption, causing enquiries to MVO. However, this particular rockfall was no bigger than many other recent rockfalls down Galways, and the seismic net gave no indication of any explosive eruption at the time.

A GPS survey of the Lee's Yard network was repeated today after Sunday's survey gave incomplete results. The new data are good and fully-processed results will be given in a subsequent report.

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.

Montserrat Volcano Observatory