Montserrat Volcano Observatory

Morning Report
Report for the period 16:00 20 January
to 07:00 21 January 1997
The current alert level is ORANGE

Further pyroclastic flows occurred in the Tar River starting at 6:25 pm. Preliminary assessment during and after the flows suggested that they were about the same size and source location as the event that occurred on the morning of Thursday, January 16, 1997. The flow also travelled all the way down the Tar River valley to the sea. The pyroclastic flows peaked at about 7:05:pm, and lasted for about one hour. Activity at the volcano throughout the rest of the night was at a slightly higher level than yesterday with small rockfalls dominating.

The ash flow produced ash clouds to about 30,000 ft. Satellite imagery at 9:15 pm revealed two separate plumes. One of high level ash that moved to the northeast and another that moved to the southwest between 5000 to 10000 feet.. There has been ash precipitation over most of the island including the east. The airport is closed.

The pyroclastic flows were preceded by a swarm of volcano tectonic earthquakes which started at about 4 pm. Up until that time there were also a few small rockfalls signals.

The MVO responded promptly to the activities by dispatching three teams of volcanologists to the east and north of the volcano. Adequate western coverage was provided from the observatory. The flows originated south of Castle Peak and traveled via the base of Perches Mountain into the Tar River valley down to the delta. Vegetation at the lower flanks of Perches were set ablaze. At no time did the reports being sent back to the coordinating center (MVO) suggest that the activity at the volcano was going to further escalate. This was confirmed on the seismic records. The teams held their positions before standing down 3 hours after the activity died down. The dome is clear this morning so a flight will be underway as soon as the helicopter is available.

The southeastern face of the dome remains unstable, and further collapses and pyroclastic flows are expected. If a major dome collapse happens, it would probably build up over a period of several hours, and could produce large pyroclastic flows in the Tar River valley and heavy ash fall downwind of the volcano. Should the collapse be very large, then an explosive eruption is possible, in the same way that it followed a major dome collapse on September 17/18. At the moment the scientists are confident that zone E, which includes Corkhill and the airport, remains safe. The Tar River area is extremely dangerous, and should not be entered in any circumstances.

Montserrat Volcano Observatory