Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 27 September
to 4 pm 28 September 1997

The sequence of explosive eruptions continues, with three more explosive events in the last 24 hours. Subsequent pyroclastic flows travelled down Tuitt's Ghaut, Tyer's Ghaut, White River and Gages Valley. Fallout from these explosions did not affect inhabited areas of Montserrat. Seismic activity related to these explosions was relatively low. The average gap between explosions is currently nine and a half hours.

The explosion at 5:15 yesterday afternoon was not preceded by any earthquake activity. Pyroclastic flows travelled down Tuitt's and Tyer's ghauts and into the Gages valley. The ash column rose to over 25,000 ft and drifted north and then east but appeared quite dilute and no ash or pumice fell on central or northern Montserrat.

The second explosion during this reporting period (at 4:28 this morning) was preceded by hybrid earthquakes, most notably three large events just before 2 am, and contained an extended explosive signal (22 seconds of long period signal) on the seismic network. The eruption column rose rapidly to at least 10,000 ft and again spread slowly northwards. The lower level ash generated from pyroclastic flows was blown westwards. Again, there was no reported ash or pumice fallout on central or northern Montserrat. Tremor following this event lasted for about 80 minutes and was accompanied by a loud roaring sound.

A third explosion occurred at 10:34 this morning. Poor visibility due to low cloud meant observations of the plume and any associated flows was difficult. However, one flow from this event entered the White River valley in the Galway's area. The plume from this event appeared to be more dilute than normal, perhaps due to the greater involvement of steam in the eruption column.

Lightening and thunder was also seen and heard in the each of the eruption columns. An observation flight made in excellent visibility this afternoon confirmed new pyroclastic flows from the three explosions in Tuitt's Ghaut (to within a few hundred feet of the airport), Tyer's Ghaut (to the Dyer's bridge), Gages valley and in White River. The shape of the summit scar and crater was very well seen, with a big scar facing northwards and a deep crater (400 to 500 feet deep) in the summit of the dome. There was very little ash or vapour emission at the time of observations.

The seismic network recorded 30 hybrid events, 8 rockfall signals and one long-period earthquake during the reporting period. Repairs to the short-period network were made today enabling the signals from St George's Hill and St Patrick's to be received again. The solar panels and EDM reflector at Lees Yard were also cleaned.

Further explosions are very likely and these could be bigger than those experienced in the last few days. Pyroclastic flows and surges could 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