Montserrat Volcano Observatory

Morning Report
Report for the period 4 pm 23 September
to 7 am 24 September 1997

There was another explosive event at the volcano last night which generated pyroclastic flows and a substantial ash cloud to over 10,000ft.

A swarm of hybrid earthquakes began yesterday afternoon shortly before 4pm. It was not a particularly intense swarm but some of the individual events were quite large. The swarm continued for several hours until 12.34am when an explosion was heard. Observations suggest that pyroclastic flows generated during the explosion were concentrated in the Gages Valley and fires were seen in this area. Seismic tremor was recorded for about half an hour after the explosion which probably corresponded to vigorous ash venting. Most ashfall from this event was in the Plymouth area.

Since about 2am the level of activity has been lower although there have been occasional hybrid earthquake and rockfall signals.

Further explosions are very likely and these could be bigger than those experienced in the last few days. The pyroclastic flow activity of the last two days has mainly been down Tyers Ghaut (that is the 'unnamed' ghaut) and Gages Valley, both of which may feed material into the Belham valley. An event directed down the Belham valley of a similar size to the one on Sunday morning which destroyed the airport would reach the Belham bridge and impact upon Friths and Salem. All those remaining in the exclusion zone are urged to leave as soon as possible.

In the event of an explosion fallout may occur anywhere on the island, so hard hats or other suitable protection should be worn. People should seek shelter in a sturdy building. Falling ash and pumice reduces visibility and makes driving conditions extremely hazardous. The wearing of ash masks is recommended outdoors. Everyone is advised to keep listening to Radio Montserrat for information on the activity.

Montserrat Volcano Observatory