Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 28 September
to 4 pm 29 September 1997

During the last 24 hours there have been three explosive eruptions at the Soufriere Hills Volcano. Pyroclastic flows generated during these events travelled down Tar River valley, White River valley, Tuitt's Ghaut, Mosquito Ghaut, Tyers Ghaut and Gages Valley. There has also been an explosion since the end of the reporting period at 4.48pm. The explosions have been closer together with an average of six hours between the last three events.

The explosion at 11.03 pm last night generated flows which travelled down the northern flanks of the volcano. During the explosion incandescent ballistics were observed blasted from the volcano, particularly over Farrell's plain and over Gages mountain.. Pyroclastic flows were observed on the northern flanks of the volcano and in Gages valley. The ash cloud rose to well over 10,000ft. A low level ash cloud drifted westwards and upper levels of the cloud drifted to the northwest. There was sand-sized fallout in Salem and finer ash fell in the Woodlands area. There were several hybrid earthquakes before the explosion but not enough to constitute a swarm.

The second explosion during this reporting period, at 6.27am this morning, generated a very dilute and steam-rich plume which just about reached 10,000ft in altitude. The ash cloud was blown west over Plymouth and the Foxes Bay area, there was no fallout in the inhabited parts of the island. Pyroclastic flows from this event travelled across the eastern part of the Farrell's plain and probably also into Gages valley. The ash venting following this event was not particularly vigorous and the resulting ash column only reached heights of 1000ft above the crater. There were a few earthquakes before this eruption, most of which were volcano-tectonic earthquakes, but they did not constitute a swarm.

The third explosion occurred at 11.23 this morning. Pyroclastic flows travelled down Tuitt's Ghaut, Mosquito Ghaut, Gages valley and White River valley. A vigorously convecting ash cloud rose rapidly to over 20,000ft and the lower part of the cloud drifted to the west-northwest causing fallout in Plymouth and the Foxes Bay area, the upper part of the cloud moved to the south east. Again, there was no fallout in inhabited areas. The ash venting following the explosion was also vigorous and generated a plume up to 4000ft above the crater.

An observation flight at midday today confirmed that recent flows have travelled down Tuitt's Ghaut as far as the confluence with Paradise River; Flows in the White River valley have reached to within about 200m of the bridge at O'Garro's. There were also new deposits on Farrell's plain and in Gages valley, there were no new deposits in Tyer's Ghaut at this time although the explosion which occurred at 4.48 this afternoon generated pyroclastic flows which entered Tyers Ghaut, they did not reach as far as Dyers bridge.

The seismic network recorded 16 hybrid events, 9 rockfall signals, four long-period earthquakes and 11 volcano-tectonic events during the reporting period. The volcano-tectonic events mostly occurred prior to the 6.27am event. The long period events all occurred during the afternoon. There were several very small hybrid earthquakes which did not trigger the seismic system.

Further explosions are very likely and these could be bigger than those experienced in the last few days. Pyroclastic flows and surges could very easily reach the Belham valley. All those remaining in the exclusion zone are urged to leave as soon as possible. If the sirens sound in this area, people should move north immediately.

When explosions happen fallout may occur anywhere on the island, so hard hats or other suitable protection should be worn. Preferably, people should seek shelter in a sturdy building and wait for the fallout to end rather than trying to move or drive anywhere during the fallout period. Falling ash and pumice reduces visibility and makes driving conditions extremely hazardous. Roads remain difficult and plenty of time should be allowed for any journey and drivers should be very careful. The wearing of ash masks is recommended at all times. Everyone is advised to keep listening to Radio Montserrat for information on the activity.

Montserrat Volcano Observatory