Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 31 January
to 16:00 1 February 1997
The current alert level is ORANGE

The level of volcanic activity has been slightly higher in the last 24 hours, with two episodes of nearly continuous rockfall and pyroclastic flow activity that produced some ash. Both periods were preceded by swarms of volcano-tectonic earthquakes. Heavy rainfall caused flash flooding in many ghauts and some damage in Plymouth.

There was heavy rainfall overnight. Large continuous seismic signals generated by flash flooding in the ghauts were identified at 7 pm on 30 January and at 3, 3:50, 4:40 and 8 am this morning. The last of these was the largest and lasted for over one and a half hours. There was flooding in parts of Plymouth near Fort Ghaut, particularly on the north bank behind George Street. At least three wooden buildings on the bank were damaged and one small wooden house was washed away completely. The water pipe under the upper Fort Ghaut bridge in Plymouth was washed away by the flood.

There were two swarms of VT earthquakes which were followed by high-amplitude seismic tremor. The first was last night, with a VT swarm between about 6:50 and 9:30 pm and tremor from about 10 pm to 00:40 am this morning. Wet ash fell in much of the area to the west and north-west of the volcano during this time. The second VT swarm was between 08:40 and 10:30 am today. This was followed by a period of high-amplitude tremor between about 11:50 am and 2:20 pm.

The second period of tremor was associated with a series of large rockfalls and small pyroclastic flows into the Tar River Valley. The largest of these travelled as far as the break in slope in the Tar River valley. Most of the flows travelled down the chutes on the eastern flank of the dome, either side of the remnants of Castle Peak. Ash clouds associated with these flows reached heights of up to 8,000 ft above sea level and drifted to the north-west on the wind. There was light ash fall in many areas, including Lees, Weekes. and Isles Bay.

Poor weather conditions hindered most field work today. The locations of the gravity stations on the western flanks of the volcano were surveyed using the GPS equipment.

The eastern face of the dome is steep, and likely to collapse soon. Any collapse is likely to be gradual, although a larger collapse cannot be ruled out. An explosion similar to that of September 1996 could result in the event of a major collapse which lasted for several hours. Zone E, which includes Cork Hill and the airport, remains safe. The Tar River Valley and the upper Galway's area are very dangerous.

Montserrat Volcano Observatory