Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 5 July
to 4 pm 6 July 1997

The alert level system has been revised by zones

Volcanic activity has been at about the same level as yesterday with a continuation of the cyclic pattern. No pyroclastic flow activity was recorded today. Hybrid earthquakes and rockfalls were the only seismic signals recorded.

Clear conditions early on 6th July allowed views of the dome from the Observatory. Incandescent blocks were observed falling from five active channels in wide area which extended from above Gages through to Mosquito Ghaut. The area above Gages was the most active. No clear views were obtained of the volcano during the day. Burning logs were observed in the lower Gages valley during a late evening helicopter flight today. These were at the front of the pyroclastic flow deposits generated on 1st July and may be due to re-ignition of the logs due to the high temperature of the flow deposits.

The tiltmeter on Chance' Peak has settled into a 12 hour cyclic pattern. No pyroclastic activity were associated with any of the two cycles recorded during the reporting period. Ash was generated at the end of the tilt cycle which was recorded at about midday today.

Forty-three rockfall signals and 37 hybrid earthquakes were recorded by the seismic network. No volcano-tectonic events were recorded.

GPS measurements were conducted on the new deformation triangle which was established with stations at Garibaldi Hill, Lees and the Waterworks. Further measurements using the GPS and EDM instruments would be made to these points during the next few days. It would be a few days before sufficient data is collected to be directly useful in the monitoring effort.

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 the most likely pathways for pyroclastic flows, but further flows in Tuitt's, Tar River or White River are possible as well. Access to Plymouth is completely restricted.

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 (UPR) arrived for a brief visit today. He would be carrying out some adjustments to the UPR's network of permanent GPS stations. Dr Alan Smith left today after a brief visit.

Montserrat Volcano Observatory