Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 13 January
to 16:00 14 January 1997
The current alert level is ORANGE

Rockfall and pyroclastic flow activity from the dome has continued during the past 24 hours, at a lower level than yesterday. More pyroclastic flows occurred late last night, although these weren't as large as the flows which occurred yesterday during the day. Several rockfalls and small pyroclastic flows occurred today, and there have been some volcano-tectonic earthquakes. There is also some evidence that the Galway's Wall has become more active, with the deposits of some landslides seen and an increase in the rate of crack opening on Chances Peak. The southeastern part of the dome remains in an unstable state, and further pyroclastic flows are likely in the next few days. A major collapse of the dome is possible, and could result in another explosion, similar to that of September 1996. It is expected that there would be several hours of a high level of pyroclastic flow activity before any explosion. At the moment, the scientists are confident that zone E, which includes Cork Hill and the airport, remains safe.

A magnitude 5.4 earthquake occurred about 20 km to the northeast of Antigua this afternoon, at 2:03 pm. The earthquake was recorded as a strong signal on all the stations of the seismic network, and was felt by many people in Montserrat. It was also recorded by seismic stations throughout the region, which allowed scientists at the Seismic Research Unit in Trinidad to compute its location. A total of 114 rockfall signals and 71 volcano-tectonic earthquakes have been recorded in the last 24 hours. This mixture of activity has not been common in the last few months, as usually the rockfalls and earthquakes occur in different phases.

Pyroclastic flows in the Tar River valley occurred between 10:15 pm and 11:05 pm last night. This activity was not as strong as the flows at midday yesterday. Observations from Harris and Whites late last night showed that there was strong glowing from the top of the southern chute, to the south of Castle Peak. Some rockfalls were also seen from the Castle Peak chute. Visual observations were made from the helicopter this morning. Castle Peak has been further eroded by the recent pyroclastic flow activity, particularly at its southern margin. The pyroclastic flow activity yesterday was to the south of Castle Peak, and formed a deep gully in the old flow deposits, and a fresh scar on the October 1 dome. There has been further growth of the October 1 dome at the top of the south chute, and this face is hot and active.

During the morning inspection flight, further landslides from the Galway's Wall were noted. These have occurred during the last few days, probably at the same time as the increase in VT earthquake activity. The extensometer instrument across one of the cracks on Chances Peak showed an extension of 3 cm during yesterday, a sudden change from the previous rate of about 0.5 mm per day. These observations suggest that the rate of deformation of the Galway's Wall has increased again, and the situation will be watched closely in the next few days.

An experimental measurement of the amount of sulphur dioxide coming from the volcano was carried out today on land and from the Police launch. Three runs were made on land this morning, and gave an average result of 830 tonnes per day. This is higher than the normal rate, and the increase is probably due to yesterday's pyroclastic flows. Further runs were made from sea this afternoon, and the results of these will be compared with the land runs.

Montserrat Volcano Observatory