Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 29 September
to 4 pm 30 September 1997

During the last 24 hours there have been a further three explosive eruptions at the Soufriere Hills volcano. Pyroclastic flows generated during these events travelled down valleys all around the volcano. There was also an explosion after the end of the reporting period at 5.44 pm. Fallout over inhabited areas has been very limited.

The first explosion of this period, at 4:48 pm yesterday afternoon, was preceded by some small volcano-tectonic, long-period and hybrid earthquakes and was followed by about two hours of moderate amplitude tremor associated with vigorous ash and steam venting. The explosion was audible in areas of central Montserrat and roaring accompanied the ash and steam venting. The eruption column and cloud was quite diffuse and steamy. Pyroclastic flows reached the Tar River delta and to below Harris Lookout in Tuitt's Ghaut. Other flows were noted in Tyer's Ghaut and in the White River. The wind blew low level ash to the west and the high level ash and pumice to the south-east, with the cloud reported to have reached well over 10,000 ft.

The second explosion was at 9:57 last night. This again produced a quite diffuse ash cloud which at low levels blew to the west and at higher levels moved slowly northwards. The eruption column was not as vigorous as many of the previous columns. Again, no fallout was reported for this event. Small volcano-tectonic earthquakes preceded the explosion over a period of several hours, but declined in the hour prior to the eruption, during which time there were several hybrid events. Tremor was at a high level for about 90 minutes after this event, associated with steam and ash venting.

The third explosion of the reporting period was at 4:44 this morning. This was again preceded by mixed volcano-tectonic and hybrid earthquakes, but with no real build-up leading to the explosion. The column and cloud were again diffuse, rising to over 10,000 ft but not depositing any material over the island. Tremor for this event only lasted about 30 minutes.

The seismic network recorded 11 hybrid events, 5 rockfall signals, one long-period earthquake and 72 volcano-tectonic earthquakes during the reporting period. Most of the larger vts and hybrids occurred during the day today (since 7:30 this morning up to the end of the reporting period), with several vts significantly larger than others seen during the current phase of activity. The vts were located at depths of 1 to 2 km beneath the crater.

Further explosions are very likely and these could be bigger than those experienced in the last few days. Pyroclastic flows could very easily reach the Belham valley from these explosions, and surges could travel up the valley sides for a considerable distance. All those remaining in the exclusion zone are urged to leave this evening. If the sirens sound in this area at any time, people should move north immediately.

When explosions happen fallout may occur anywhere on the island, so hard hats or other suitable protection should be worn. Preferably, people should seek shelter in a sturdy building and wait for the fallout to end rather than trying to move or drive anywhere during the fallout period. Falling ash and pumice reduces visibility and makes driving conditions extremely hazardous. Roads remain difficult and plenty of time should be allowed for any journey and drivers should be very careful. The wearing of ash masks is recommended at all times. Everyone is advised to keep listening to Radio Montserrat for information on the activity.

Montserrat Volcano Observatory