Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 26 November
to 6 pm 27 November 1997

Today volcanic activity was at a significantly higher level than over the last few weeks with an extended period of pyroclastic flow activity over Galways Wall.

Between 16:00 yesterday and 16:00 today there were 17 long-period earthquakes, 12 of which preceded rockfalls, 2 hybrid earthquakes, and 158 rockfall signals.

A period of pyroclastic flow activity started at 14:45, and is ongoing at the time of reporting although at a lower amplitude and in a more pulse-like manner than at the start of activity. There were no precursory signals suggesting that pyroclastic flows were going to occur. The pyroclastic flows reached the new fan at the end of the White River valley at O'Garras, but did not enter the sea. The flows were generally slow moving and did not convect vigorously. The amplitudes of the seismic signals were not as high as the major dome collapses at the beginning of November, but appear to be made up of semi-continuous rockfall activity.

The rockfall activity off the north-eastern face of the dome above Tuitts Ghaut that was observed yesterday was not apparent today, although vigorous steaming continues on the Tar River flank of the dome.

Results from the GPS survey completed yesterday of the sites at Harris, Windy Hill, Whites and Brodericks show that the positions of Whites and Windy Hill have not changed significantly since they were last measured a month ago. The height of the Brodericks site continues to increase at a slow rate.

The pyroclastic flow activity of today indicates that the dome is still growing and that further flows could occur down any of the ghauts around the volcano with little warning. If the activity continues at the same level, it is possible that explosive behaviour may resume. The level of ash in the atmosphere in Woodlands, St Peter's and in St John's, as averaged over the last 24 hours, has remained low.

Montserrat Volcano Observatory