Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 11 January
to 16:00 12 January 1997
The current alert level is ORANGE

Rockfall and pyroclastic flow activity from the October 1 dome has again been at a relatively low level during this reporting period. Some minor changes in the shape of the dome have been noted which may indicate that activity has switched from extrusive in style (pushing lava to the surface) to intrusive (swelling of the dome as lava pushes up inside). Certain parts of the dome remain unstable, so further pyroclastic flows are expected in the next few days. A major collapse of the dome is still a possibility and could result in another explosion, similar to the September 1996 event. 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.

Visual observations were made today from White's Yard and areas to the north of the volcano. Some swelling of the northwestern part of the dome was noted and further rockfall activity and possible extrusion on the north face was also seen. Visual observations during yesterday evening showed that only one area of the dome was very active, namely the steep face above Castle Peak which has been the main source of rockfalls and pyroclastic flows over the past couple of weeks. Other areas of the dome which had been glowing for most of the week were not glowing very much, suggesting that the rate of growth of the dome has slowed over the past couple of days.

A visit to the pyroclastic flow deposits on the delta at the end of the Tar River valley was made late yesterday afternoon. Temperature measurements of the flows, which are thought to have just reached the sea during Wednesday night, showed that they are still very hot, with a temperature of 420 degrees centigrade recorded at a depth of 45 cm. An ash-cloud surge associated with these flows reached very close to the Tar River Estate House.

A visit was made this afternoon to Chance's Peak, where the cracks close to Galway's Wall were measured, a GPS survey was set up and some checks were made on other equipment. The cracks continue to open, with an extension of 2.7 cm measured over the past 12 days on the crack closest to Galway's Wall - this is about the same rate as has been seen over the past month or so. The GPS survey will be completed tomorrow.

The seismic activity was at a relatively low level today, though with a peak in rockfall activity between 1 and 4 pm this afternoon; rockfalls produced light ashfalls to the west of the volcano. A total of 36 rockfalls were recorded, a significant decrease from the total yesterday. A regional earthquake was the only other seismic signal recorded during this period.

Dr Rick Hoblitt of the US Geological Survey departed Montserrat today after a month-long tour of duty.

A film made last year on the current eruption of the Soufriere Hills volcano by National Geographic will air tonight at 8 pm local time on Channel 9 (TBS).

Montserrat Volcano Observatory