Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 05 September
to 16:00 06 September 1996

Activity at the Soufriere Hills volcano during this reporting period has remained at a relatively low level, similar to that observed during yesterday. Rock falls have continued throughout the day, the largest of which have led to the generation of pyroclastic flows within the Tar River valley.

Seismicity during the day has again been dominated by volcano-tectonic earthquakes and rock fall events. A total of 74 volcano-tectonic earthquakes were recorded during the past 24 hours; these occurred in two distinct swarms, an hour long one yesterday evening (5 September) between 17:04 and 18:04 and the other between 02:38 and 06:17 this morning (6 September). All of these events were located beneath the crater at depths of 1 to 2 km. Rock fall events totaled 49 during this reporting period, an almost identical number to yesterday. A series of rock falls and small pyroclastic flows occurred between 18:51 and 19:50 last night, with further pyroclastic flows reaching as far as the Tar River Estate House at 09:37 and 10:13 this morning. One long period event and 39 hybrid events were also recorded, the hybrid events mainly occurring at the same time as the volcano-tectonic swarms. Low amplitude broadband tremor was near continuous during the period.

Visibility during the day was moderate, with brief observations of the dome possible. The scar left from the collapse events of earlier in the week has started to refill with newly extruded material, and the channel leading from the base of the scar has been filled in with repeated rock falls. A small area of new rock fall was noted on the northern flank of the dome during a helicopter inspection, and a small pyroclastic flow was also seen to the south side of Castle Peak. Ash generated during today's activity has been blown westwards over the Plymouth and Kinsale areas; however, dry conditions have led to some remobilisation of ash deposited earlier in the week in the Salem and Old Towne areas.

EDM measurements were not made today.

Sampling was undertaken today at the edge of the pyroclastic flow delta; the new rock collected will be analysed at a number of specialist laboratories and the results of these and previous analyses will enable the scientists to develop a better understanding of the volcano.

Further rockfalls and pyroclastic flows will occur as the lava dome continues to grow within English's Crater, but indications at the moment are that the pyroclastic flows will be confined to the Tar River valley area. Areas affected by associated ashfalls will obviously depend on the direction and strength of the wind at the time. Dust masks should be worn at all times in ashy environments, and drivers should exercise caution and consideration for other road users.

The Tar River Valley and surrounding areas continue to be extremely hazardous, and should not be entered under any circumstances. We urge individuals who persist in ignoring this advice to think very seriously before making trips to these highly hazardous zones.

Montserrat Volcano Observatory