Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 18 January
to 16:00 19 January 1997
The current alert level is ORANGE

The level of activity has been a bit lower over the last 24 hours. The main seismic activity has been swarms of volcano-tectonic earthquakes. There has been continued growth of the October1 dome.

A total of 56 volcano-tectonic earthquakes were recorded. Most of these occurred in two swarms, from 6 pm to 7:30 pm last night, and 5:15 am to 6:45 am this morning. Most of the earthquakes were too small to enable their locations to be calculated, but the larger earthquakes were as usual located at shallow depths beneath the crater. In addition, 42 hybrid and 9 long-period earthquakes were recorded. There were also 44 rockfall signals, a similar number to yesterday.

Only brief views of the dome were possible today, due to low cloud cover. The shape of the dome has changed since yesterday, with further rapid growth of the October 1 dome near Castle Peak. There has been growth in this area since the large pyroclastic flow on Thursday morning. There were few rockfalls from the dome, but the north and northeastern sides were more active than usual.

A GPS experiment was carried out at Whites and Harris today, to help constrain the errors in the GPS technique. Further gravity measurements were made, to extend one of the radial lines on the eastern side of the volcano.

The south-eastern part of the dome remains in an unstable state, and further pyroclastic flows will occur in the next few days. A major collapse of the dome is possible. Should this occur, another explosion similar to that of September 1996 could result. It is however expected that there would be several hours of high level pyroclastic flow activity before any explosion. Zone E, which includes Cork Hill and the airport, remains safe.

Dr John Shepherd, Mr John Power and Dr Maggie Mangan arrived in Montserrat today to join the MVO staff. Drs Simon Young and Jenni Barclay left on Friday, and Dr Mark Stasiuk left today.

Montserrat Volcano Observatory