Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 20 October
to 6 pm 21 October 1997

There has been one explosion in the last 24 hours. This explosion was preceded by an earthquake swarm which began at 9:20am and was comprised of both VT and Hybrid events which were broadly spaced in time.

The explosion occurred at 11:39am today and produced initial pyroclastic flows that travelled rapidly down the Tar River valley to the sea. These were followed by pyroclastic flows in Tuitt's Ghaut and across Farrell's Plain. Flows were also observed down to the lower soufriere region in the Gages valley. However very few ballistics were observed in proximal areas and the ash column rose swiftly to 38,000 feet spread out and drifted slowly Northwest. Large areas of the North-western part of the island experienced pumice fallout with maximum sizes of 2cm in Salem. The northern part of the island including St Johns and Geralds received light ash fall. Ash clouds generated by the pyroclastic flows were blown NE at lower heights

Between 4 o'clock yesterday afternoon and 4 o'clock today there were 37 hybrids, 23 VTs, 13 long period earthquakes and 10 rockfall signals scattered throughout the reporting period. The explosion was followed by a period of tremor and ash venting - this venting was especially vigorous this afternoon with plumes of ash up to 10,000 feet formed up to an hour after the explosion.

The GPS campaign including measurements at Harris, Windy Hill and Whites undertaken yesterday showed that the northward movement, detected over the last 5 months, has slowed somewhat.

More explosions are expected and larger explosions could occur without any warning change in seismicity. Recent explosions have sent pyroclastic flows into Plymouth, into the upper part of the Belham Valley and to the sea in the Tar and White rivers, and future flows will travel further still. Mudflows are likely to continue in the ghauts as long as the rain continues. These mudflows could be hot and it is extremely dangerous to be in any ghauts in the southern part of Montserrat at the moment.

All residents of Montserrat are reminded to be vigilant, to avoid entering the evacuated zone and to stay tuned to Radio Montserrat for further information.

Montserrat Volcano Observatory