Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 02 February
to 16:00 03 February 1997
The current alert level is ORANGE

Volcanic activity within the last 24 hours was highlighted by two episodes of high amplitude volcanic tremor during which a few pyroclastic flows were generated. The largest pyroclastic flow which occurred this morning had associated ash clouds that produced ashfall on the west and north-west of the island. Both periods of volcanic tremor were preceded by volcano-tectonic earthquake swarms The first was followed by a period of high-amplitude seismic tremor. Earthquake and rockfall activity was at a higher level than yesterday.

The first VT earthquake swarm started during the last reporting period at 2:16 pm yesterday and was followed by the period of volcanic tremor which got started at 5:35 pm and reached a peak at 7:00 pm. At the peak of this event two small pyroclastic flows were generated. A small ash column was produced by the flows. The largest travelled to the break in slope in the Tar River valley. The second VT earthquake swarm started this morning at 5:00 am. A total of 49 earthquakes occurred before the second period of volcanic tremor got underway at 7:45 am. This episode peaked at 8:30 am with three successive pyroclastic flows. The largest of these crossed the delta and just made it to the sea. The ash column associated with this flow rose above the crater to a height of about 8000 ft above sea level.

A total of 79 volcano tectonic and 14 hybrid earthquakes were recorded since 4:00 pm yesterday. The rockfall level was higher than yesterday with 66 events recorded. Most of the earthquakes occurred at shallow depths beneath the crater.

A late afternoon reconnaissance flight to closely inspect the tremor activity yesterday revealed that the activity was focused in an area above Castle Peak. Small quantities of fluidised lava was shed occasionally from a steep face of the dome. It is quite likely that the tremor is produced as the lava is pushed from within the dome to the surface. Visual observations were also made from the helicopter after the pyroclastic flows this morning. It was discovered that the remains Castle Peak were totally eroded by the earlier activities.

A GPS campaign was undertaken today at the Long Ground, Windy Hill, Whites and Harris stations.

The eastern face of the dome is steep, and likely to undergo further collapse soon, perhaps later this evening. 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