Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 21 January
to 16:00 22 January 1997
The current alert level is ORANGE

The volcano remained quiet today, with only small rockfalls. However, showed that rapid dome growth is continuing, and the void caused by the dome collapse on Monday night is nearly filled. Two swarms of volcano-tectonic earthquakes were also recorded.

Observations were made from the helicopter and from Whites today. There has been a lot of new dome growth since Monday, and a large flower-shaped extrusion is now present in the void caused by the recent pyroclastic flows. The surface of this extrusion is blocky and angular, and it has grown to a height just above the edges of the void. There are several large radial cracks running through the new extrusion, which look as if they extend to its base. There have been no noticeable changes to the rest of the dome.

A total of 54 volcano-tectonic earthquakes were recorded. Most of these occurred in two swarms between 9:20 pm and 10:27 pm, and 7:51 am and 9:47 pm. All the earthquakes that could be located were at shallow depths beneath the crater. There were 20 rockfall signals, a decrease in numbers since yesterday. Five hybrid and five long-period earthquakes were also recorded.

The northern EDM triangle was measured this morning. The lines between Windy Hill, St George's Hill and Farrells showed no change since the network was last measured on 5 January.

Gravity measurements were made this morning, along a line from Broderick's down to the sea. A trip was made to Chance's Peak this afternoon, to clean the reflector that is used for EDM readings, and to measure the width of the cracks on Chance's Peak. The results of these measurements will be reported tomorrow.

The south-eastern and sector of the dome is becoming unstable. Further pyroclastic flows are likely in the next few days. Although the dome is likely to collapse in small chunks, producing small to large pyroclastic flows, a major collapse can not be ruled out. Should this occur, another explosion similar to that of September 1996 could result. It is however expected that there would be several hours of high level pyroclastic flow activity before any explosion. Zone E, which includes Cork Hill and the airport, remains safe.

Montserrat Volcano Observatory