Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 13 July
to 4 pm 14 July 1997

The alert level system has been revised by zones

The level of activity at the volcano has decreased since yesterday. The seismicity is dominated by rockfalls signals.

The volcano was overcast for most of the day, although some views were obtained of the flanks of the dome. Theodolite measurements made from the MVO and Garibaldi Hill yesterday indicate that the highest point on the dome is at least 950 metres. This is an area located to the north-west of the dome above the Gages valley. Photographs taken during clear conditions yesterday have not yet been processed and so no volume estimates are currently available.

The number of rockfall signals has decreased further since yesterday. 53 rockfall signals, 4 long period earthquakes and 2 hybrids were recorded by the seismic network today. There were no volcano-tectonic earthquakes recorded.

The EDM line between Waterworks and Lees Yard was again surveyed twice today. The data collected from these stations does not currently define a consistent trend.

The location of a new observation site at Jack Boy Hill was precisely determined with the GPS equipment today. This station would be used for future theodolite measurements and for static photographs.

The Chances Peak tiltmeter continue to define an overall deflationary trend on the x-axis. Apart from this there were no changes on this instrument reading since yesterday.

Residents should note that pyroclastic flow and ash eruptions have occurred during the past week with no preceding increase in seismicity or direct association with seismicity or tiltmeter readings. This means that people entering the designated exclusion zone put themselves at extreme risk. People in the northern and central 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.

Ms Joan Latchman of the Seismic Research Unit in Trinidad left today after another tour of duty at the MVO.

Montserrat Volcano Observatory