Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 14 July
to 4 pm 15 July 1997

The alert level system has been revised by zones

The level of activity at the volcano is about the same as yesterday. The seismicity is dominated by rockfalls signals.

The volcano was overcast for most of the day, and so no views were possible of the dome. A helicopter flight over the volcano early this afternoon showed that there were new pyroclastic flow deposits in Mosquito Ghaut, Gages valley and over Galway's wall. The largest flow, which occurred on 13 July at 14.30, went to a point just above Gages village. A more recent flow had stopped by Gages Lower Soufriere.

The number of rockfall signals is about the same as yesterday. 64 rockfall signals, 1 long period earthquake and 1 hybrid 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 Chances Peak tiltmeter continues to define an overall deflationary trend on the x-axis. Apart from this there were no changes on this instrument reading since yesterday.

Although there appears to be very little seismic activity from the volcano, there have been periods in the past when the dome has continued to grow with few earthquakes apart from rockfalls. Thus it is probable that material is currently building up above Gages wall and Mosquito Ghaut, and the potential for large pyroclastic flows onto the northern and western flanks into the Central corridor and Plymouth is significant.

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.

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. Rick Hoblitt of the US Geological Survey left today after another tour of duty at the MVO and Mr. Chandrapath Ramsingh arrived today for about a month.

Montserrat Volcano Observatory