Montserrat Volcano Observatory

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

Activity at the volcano has been elevated today with a large number of volcanic earthquakes and rockfalls.

Between 16:00 yesterday and 16:00 today there were 31 long-period earthquakes, 249 hybrid earthquakes and 79 rockfall signals. Some of the hybrids were high amplitude, although most of them were relatively small. Rockfalls continued throughout the day. Visual observations of the volcano indicated that steam and ash venting occurred for most of the afternoon with the plume extending over Chances Peak towards Plymouth.

The level of ash in the atmosphere in St Peter's and in St John's, as averaged over the last 24 hours, remained low.

The volume of the pyroclastic fan at the mouth of the White River was calculated today. Currently, there are 4.5 million cubic metres of material in the fan, and all deposits in the White River, including the fan, total 13.6 million cubic metres. This is an increase of 5.5 million cubic metres since the last survey of the valley on 30th May, but most of the debris was deposited as a result of the dome collapses on 4th and 6th November.

The dome is still growing and the growth area may switch rapidly at any time. The increase in hybrid earthquakes today suggest that the activity is changing and large pyroclastic flows or explosions may occur in the near future. Although the main activity is currently in the south-west sector of the volcano, further pyroclastic flows are likely in any of the ghauts around the volcano.

Montserrat Volcano Observatory