Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 25 November
to 6 pm 26 November 1997

Today seismic activity was at similar level to yesterday with small hybrid earthquakes, long-period events and rockfall signals recorded. Visibility was better than over the past few days, and brief views of the dome were obtained.

Between 16:00 yesterday and 16:00 today there were 13 long-period earthquakes, 5 of which preceded rockfalls, 19 hybrid earthquakes, and 46 rockfall signals. The hybrids remained very small again today, and many of those observed on the drums did not trigger the networks and so are not included in the count.

A helicopter flight today and views from Jack Boy Hill and Old Towne revealed that rockfall activity is now occurring off the north-eastern face of the dome above Tuitts Ghaut and into Tar River as well as over Galways Wall.

A GPS survey was completed today of the sites at Harris, Windy Hill, Whites and Brodericks. These data are currently being processed and results should be available in a future report. During this survey, the total station reflector at Lees Yard was cleaned and measurements were subsequently made from the old observatory site in Old Towne to the reflector. These data show that there has been continued slow shortening on this line since it was first measured in July, 1997. During the flight, solar panels at St. Patricks and Lees Yard seismic stations were cleaned; this should ensure that the seismometers will receive adequate power. Samples were also collected from material deposited on the White River pyroclastic fan. This material probably originated from the dome extruded into the scar formed by the September to October explosions.

It has to be assumed that the dome is continuing to grow, albeit at a slow rate. This means that pyroclastic flows could occur down any of the ghauts around the volcano with little warning. The level of ash in the atmosphere in Woodlands, St Peter's and in St John's, as averaged over the last 24 hours, has remained low.

Montserrat Volcano Observatory