Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 18 October
to 16:00 19 October 1996
The current alert level is AMBER

Activity at the volcano has been at about the same level as yesterday with volcano-tectonic earthquakes being the most common seismic signal recorded and growth of the October 1 dome continuing. A few rockfall signals and long-period earthquakes were also recorded by the seismic network. Very clear conditions provided another day with excellent views of the crater area.

Twenty-one volcano-tectonic earthquakes, 4 long-period events and 4 rockfall signals were recorded during the period. Most of the VT's occurred during the period 16:00 to 20:00 on 18 October, although a few were also recorded today. There has been a decrease in rockfall signals although very small rockfalls continue to be observed from the eastern flank of the October 1 dome. The long-period events recorded today were small and none were associated with ash clouds. Tremor on the Gages seismic station was intermittent and of variable amplitude for most of the period.

Very good visibility for most of the day once again allowed clear views of the crater area. The new dome continues to grow with some changes in shape. The eastern face of the new dome does not appear as steep as it did previously but now has a number of small stubby spines and blocky protrusions. The rear western wall of the scar was observed from Windy Hill and appear to be essentially unchanged. The October 1 dome is not yet visible from this side of the volcano but with current rates of growth this may change during the next few days.

No COSPEC measurements were again possible today due to unfavourable weather conditions.

EDM measurements were conducted on the southern triangle to Chances Peak and the eastern triangle to Castle Peak today. Measurement of the eastern triangle is currently in progress and the results from both of these lines would be available tomorrow. Results from yesterday's measurements indicate that the Whites to Castle Peak line shortened by 1.4 cm during the period 14-19 October while the Long Ground to Castle Peak line shortened by 3.3 cm during the period 10-19 October.

Additional photographs were taken today of the dome complex from Windy Hill. These would be compared with photographs taken previously along with results of the GPS survey conducted yesterday to obtain estimates of dome volume and magma effusion rates.

The volcano remains in an active and highly dangerous state. Further activity, possibly leading to an explosive event could occur with little warning in the near future. Everyone who enters the evacuated zone must remain alert and be ready to move at short notice. Individuals who go beyond the Long Ground area into the Tar River valley are risking death.

Professor Geoff Wadge of the University of Reading arrived on island on Thursday 17 October for a one week visit. Dai Stewart and Peter Day of the British Geological Survey left Montserrat yesterday after a three week visit during which they installed the new broadband seismic network. Chloe Hartford of Bristol University left the island today after a two month visit during which she assisted with monitoring of ground deformation and dome volume changes at the volcano.

Montserrat Volcano Observatory