Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 8 July
to 4 pm 9 July 1997

The alert level system has been revised by zones

Visible activity at the volcano has increased since yesterday although there has been a reduction in seismicity.

The cyclic pattern defined by the Chances Peak tilt station has continued with another peak at a about 4:00 am this morning. There were no hybrid swarms associated with this cycle. There were two periods of increased activity during the day. The first, which involved increased ash venting lasted for about 2 hours and began at 5:30 am today. Several sluggish ash plumes were generated which reached up to 10,000 ft and drifted towards the east. One small pyroclastic flow which occurred down Mosquito Ghaut was observed at 6:22 am. The second period involved generation of small pyroclastic flows in Mosquito Ghaut and the Gages valley between 13:45 to 14:00.

31 rockfall signals and 1 hybrid earthquake were the only signals recorded by the seismic network today. One regional earthquake which was located near Venezuela was recorded by the seismic network.

The new EDM line established yesterday between Waterworks and Lees Yard was again successfully surveyed. There were no changes in the line length. A new reference point for theodolite and EDM measurements was also precisely established at the top of St George's Hill using the GPS equipment.

The volcano has been very cloudy today and no clear views have been obtained.

It seems likely that the cyclic nature of the activity will continue with repeated periods of pyroclastic flows giving rise to ash clouds away from the volcano, and thus people in the safe zones should stay alert and listen to Radio Montserrat. The current area of activity in the crater makes Mosquito Ghaut and Gages valley the most likely pathways for pyroclastic flows, but further flows in Tuitt's, Tar River or White River are possible as well.

Plymouth is particularly vulnerable since pyroclastic flows have begun to enter the Gages valley without warning and have the potential to reach the coast. Persons entering these areas place themselves in extreme danger.

The Belham River valley is also an area for anxiety over safety. It may provide a pathway for further pyroclastic surges and there is also a risk of hot mudflows which may form rapidly if there is a period of heavy rain. Mudflows travel extremely fast and may be near boiling point, they may extend much further along the Belham River valley than the pyroclastic surges. The pyroclastic flow and surge deposits will remain extremely hot for several days. Residents must not approach, attempt to handle or walk on the deposits because of the risk of severe burning. Residents and workers are also reminded to wear a dust mask when there is ash in the air.

Dr. Glen Mattioli of the University of Puerto Rico left Montserrat today after a brief visit.

Montserrat Volcano Observatory