Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 19 October
to 6 pm 20 October 1997

There have been three explosions in the last 24 hours. The first two explosions had no seismicity beforehand but the explosion this afternoon was preceded by a swarm of volcano-tectonic earthquakes.

The first explosion took place at 9:27 yesterday evening, pyroclastic flows were observed to go down Tuitt's Ghaut and across Farrell's Plain, and the ash column went up to 18,000 feet and drifted Northwest. The second explosion occurred at 5:05 this morning and was poorly observed due to the darkness and low cloud levels. The third explosion, at 15:15 this afternoon, was more vigorous than the others and pyroclastic flows reached the sea down the Tar River Valley. There were also pyroclastic flows down Gages valley to Lovers Lane, down Tuitt's Ghaut to Bethel and for a few 100 metres down the un-named Ghaut. Flows were observed to the South of the volcano between the White River and Fort Ghaut but no helicopter flight has yet been made to check exactly where these flows went.

The first two explosions of this period were preceded by nothing more than the background level of small rockfalls. The explosion this afternoon, however, was preceded by a swarm of 21 volcano tectonic earthquakes and 18 hybrids which started at 11:30 this morning. Between 4 o'clock yesterday afternoon and 4 o'clock this afternoon there were 11 more hybrids, 11 long period earthquakes and 7 rockfall signals scattered throughout the reporting period. All three explosions were followed by periods 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 heavy rain has caused a number of mudflows around the volcano, and mud has formed a new fan of deposits 100 m wide on the golf course just before the beach. A GPS survey was carried out today with measurements being made at Harris, Windy Hill and Whites. The results from this survey will be reported in the near future.

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