Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 17 June
to 4 pm 18 June 1997
The current alert level is ORANGE

There was a significant episode of pyroclastic flow activity last night in Mosquito Ghaut and, to a lesser extent, in Gage's Valley.

After being at a low level during the late afternoon yesterday, the level of pyroclastic flow and rockfall activity increased rapidly last night and reached a peak between 11.00pm and 11.40pm. The activity was watched from the observatory and by an MVO field team who went to Bramble Airport. There were many rockfalls down the eastern slopes of the dome, rockfalls into Tuitt's Ghaut and pyroclastic flows down Mosquito Ghaut and the top of Fort Ghaut. An early morning inspection of deposits was made from the helicopter just after dawn which revealed that the largest pyroclastic flow had gone down Mosquito Ghaut into Paradise Ghaut and Paradise River, terminating just below the Guadeloupe Bends on the cross island road. Ground scorching was seen up to 200m from Mosquito Ghaut on the fields of Riley's Estate due to side surges being driven in the wind, and similar burning of vegetation took place on the sides of the Paradise River valley, within a few yards of the road at Harris's. The maximum run-out distance of these flows was about 4km, the source of the material leaving a scar in the dome above Mosquito Ghaut. Smaller pyroclastic flow deposits were seen in the Gage's Valley, at the top of Fort Ghaut, having gone about 200m further than the flows which occurred on Monday afternoon (16 June), that is about 2km from the crater rim. These latter deposits originated from material from the main pyroclastic flow avalanche spilling round the high point of the crater rim between Mosquito Ghaut and Gage's Valley.

The level of activity declined sharply after midnight and remained low until about 1pm today when a short burst of moderate activity generated a few small pyroclastic flows in Mosquito Ghaut.

The seismic activity today has been similar to that of yesterday, with rockfall signals dominating: there were 154 of these in the last 24 hours. The level of earthquakes remained low, with no volcano-tectonic earthquakes, 4 hybrid events and 5 long-period earthquakes recorded.

An EDM survey of the western triangle was undertaken today. No significant changes in line lengths were seen.

The top of the volcano remained in cloud all day.

Further pyroclastic flows could occur in any direction, especially in Mosquito Ghaut, Tar River valley or Gages Valley. Access to Plymouth remains restricted. Corkhill remains safe at this time. WH Bramble Airport was open today.

Montserrat Volcano Observatory