Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 8 January
to 16:00 9 January 1997
The current alert level is ORANGE

The October 1 dome has been very active during this period, producing many rockfalls and pyroclastic flows. The level of activity has increased again in the last 24 hours, with many pyroclastic flows reaching level with the Tar River Estate House. Peaks in activity late yesterday afternoon, around midnight last night and around 6 am this morning suggest some pulsing of activity, but the general trend through the period has been of increasing activity. A major collapse of the dome could happen any time during the next few days, and there is a chance that this will lead to an explosion similar to that of 17/18 September. At the moment, the scientists are confident that zone E, which includes Cork Hill and the airport, remains safe. However, the situation could change rapidly, and residents of Montserrat should remain alert and continue to listen to Radio Montserrat.

Visibility has been good today, with all of the dome visible. Rockfall activity has produced an ash plume at an altitude of about 4,000 feet out to about 50 miles west of Montserrat, with larger pyroclastic flows producing ash to 6,500 feet. Observations of pyroclastic flows from Whites suggested that they reached beyond the Tar River Estate House - most are running down the south side of the Tar River valley and are sourcing from the most active area behind Castle Peak. Much of the eastern and northern flanks of the dome are also active.

Latest estimates of the volume of the lava dome in English's Crater show that it is about the same size as the dome immediately prior to collapses in July, August and September last year, and it is unlikely that the dome will grow very much more without some major collapses from it.

The seismic activity continues to be dominated by rockfalls and pyroclastic flows. A total of 184 rockfalls were recorded today, another increase from the number recorded yesterday. The size of the largest pyroclastic flow signals has also increased again since yesterday. Other seismic signals included 39 hybrid events, one volcano-tectonic earthquake and 8 long-period events. Overall, the seismicity has continued to increase slightly through the day.

COSPEC measurements made today gave a result of 1130 tonnes per day of sulphur dioxide, a marked increase in gas production rate from previous measurements yesterday and during the past few weeks. This increase in gas production is consistent with an imminent collapse of the dome and occurred prior to collapses in August.

Dr Randy White of the US Geological Survey left Montserrat today after a 4 week tour of duty assisting with seismological aspects of the monitoring. Rob Watts of BGS also left today for a short break.

Montserrat Volcano Observatory