Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 10 January
to 16:00 11 January 1997
The current alert level is ORANGE

The level of rockfall and pyroclastic flow activity from the October 1 dome has decreased during this period. No major changes in the shape of the dome have been seen. However, the dome remains unstable, so further pyroclastic flows are expected in the next few days. A major collapse of the dome could result in another explosion, similar to the September 1996 event. At the moment, the scientists are confident that zone E, which includes Cork Hill and the airport, remains safe. However, the situation could change rapidly, and residents of Montserrat should remain alert and continue to listen to Radio Montserrat.

Observations of the dome have been made from Whites, Harris' and from the helicopter. There seems to have been few changes in the dome since yesterday. There is unstable material at the top of the chute through the middle of Castle Peak- this chute has been the source of many of the recent pyroclastic flows. The unstable material is composed of slabs of fresh lava that have been extruded in a butterfly-shaped structure during the last few days. No major changes were seen in the northwest of the October 1 dome, which has grown recently.

The seismic activity was at a lower level than yesterday, with peaks in rockfall activity between 9 pm and 12 am last night, and 11 am and 3 pm today. A total of 76 rockfalls were recorded, a decrease from the 103 signals recorded yesterday. Other seismic activity continued at a low level, and included 8 small volcano-tectonic earthquakes, 5 hybrid earthquakes, and four long-period earthquakes.

COSPEC measurements were made today along a line to the southwest of the volcano. The runs gave an average value of 410 tonnes per day of sulphur dioxide emission. This is similar to the value recorded yesterday. The peak in sulphur dioxide of 1100 tonnes per day measured on Thursday was probably due to the partial collapse of the dome on Wednesday night.

A survey of the dome was carried out today using the helicopter. The survey was highly successful, with over 100 points on the dome and talus slope measured with the laser-ranging binoculars. The results of the survey are still being processed, and will hopefully give an accurate measure of the rate of dome growth in recent days.

Mr Lloyd Lynch from the Seismic Research Unit in Trinidad arrived back in Montserrat today. Mr Lynch will be taking over as Chief Scientist of MVO next week. Dr Ricky Herd from the British Geological Survey rejoined the monitoring team after a short break.

Montserrat Volcano Observatory