Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 18 October
to 6 pm 19 October 1997

There has been just one explosion during this reporting period, at 5:13 this morning. Seismic activity was relatively high prior to this event and has continued at an elevated level during the day. Heavy rain and low cloud has prevented any observations during today.

The explosion this morning gave a large signal on the seismometers but, due to low cloud, no eruption column could be seen. Low level ash from pyroclastic flows could be seen drifting westwards and vigorous ash and steam venting followed the explosion. Pyroclastic flows were seen in Tyer's Ghaut which travelled into the upper part of the Belham valley beyond Dyer's towards Cork Hill. Due to the poor visibility during the event and throughout the day, it is not known where else pyroclastic flows went from this event.

The explosion was preceded by an intense swarm of hybrid and dominantly volcano-tectonic earthquakes during the 6 hours prior to the explosion. Some long-period events and large rockfalls were also recorded during this period. Following the explosion, the seismic records have been dominated by rockfall and pyroclastic flow signals which indicate activity mainly in the Tar River valley.

The heavy rain has caused a number of mudflows around the volcano, and a mud-rich flood was seen by observers in the Belham River during this morning. Rain may also have induced instability on the dome leading to the higher than normal number of rockfalls and pyroclastic flows.

The rain has kept ash levels down today and the amount of dust in the atmosphere was recorded as low both in the Central and Northern zones.

Larger explosions from the volcano could occur without any changes in the seismicity or other parameters. 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