Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 on 16 March 1996
to 16:00 on 17 March 1996

Seismic activity has increased in the last 24 hours, and 40 long-period signals have been recorded. Most of these are associated with rockfalls from the dome and many have produced ash clouds. Overnight, the size of the long-period events increased and many of them were recorded at all the seismic stations in the network. In particular, large signals were recorded at 2008 and 2157. The size of the events has decreased again today. Three volcano-tectonic earthquakes also occurred, two at a depth of 3 km beneath Harris's, and one at about 1 km depth beneath the crater.

The eastern EDM triangle, between Long Ground, Whites and Castle Peak was measured today. No changes were detected in the line lengths to Castle Peak since they were last measured yesterday, and data collected over the last 6 days suggests that the rate of movement of Castle Peak may be decreasing. The line from Tar River to Castle Peak was also measured, and showed a shortening of 13 mm over the last 18 days, a rate less than the average of 1 mm per day which has been maintained over the last few months.

Visual observations were made today from the helicopter and from the Farrell's observation point. Many rockfalls were observed in the areas of most active dome growth, in the north, northeast and southeast. A new spine was spotted in the centre of the dome. Numerous ash clouds have been produced over the last 24 hours, and many of these have lead to light ashfall in Plymouth and surrounding areas.

Although there has been a slight increase in seismic activity and rockfalls the change should not cause undue concern.

Dr Andrew Allen left Montserrat this afternoon, carrying the particle and gas samples that have been collected from various points over the last week. The samples will be analysed in the UK and the results will be available shortly. Dr Joe Devine arrived on island on Thursday. He will be visiting for 10 days to help with the general running of the Observatory.

Montserrat Volcano Observatory