Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 11 July
to 16:00 12 July 1996

Activity at the Soufriere Hills Volcano during this reporting period was significantly lower than yesterday. It was dominated by small to moderate sized rockfalls from the lava dome.

Only 9 rockfall events were recorded. The largest of these occurred at 22:04 on July 11 and 12:37 on July 12. There were no reports of ashfall from either of these. There were 10 long period earthquakes and 11 hybrid earthquakes in this reporting period, an increase on the numbers recorded yesterday. Four (4) volcano-tectonic earthquakes were recorded. Two of these were located to the north of the crater at shallow depths and the other two were too small to be located. Two small regional earthquakes were also recorded.

Visibility was fairly good for much of the day, giving good views of the lower slopes of the dome. The entire dome was visible for short periods of time. During a helicopter inspection, it was clear that there were some small, new rockfall deposits on both the south and northeast sides of the dome. The wet material on the northeastern slope of the dome, around the whaleback feature, has dried out in places and there are two well-formed erosion chutes there. There were no new deposits over Gages Wall or up against Galways Wall.

GPS and EDM measurements were made on the stations in the eastern triangle. The GPS data is still being processed. New software was installed on the GPS controllers to allow collection of real-time GPS data. A programme of real-time measurements will start tomorrow and will enable short-duration fluctuations to be recorded. The changes in EDM slope distances from LongGround and Whites to Castle Peak were a few mm. The height to the top of the dome was measured at 3088 ft, about 5 ft higher than the value obtained on 07 July 1996.

No COSPEC measurements of the SO2 level in the volcanic plume were carried out today.

Installation of a closed circuit television camera on Perche's Mountain was completed today. The signal is transmitted to the observatory and will be used to help monitor the dome.

Dr. Jean-Christophe Komorowski of the Institut de Physique du Globe in Paris arrived on 10 July and will be participating in volcanological studies of the volcano. Dr William Ambeh, Seismic Research Unit, and Dr Anne-Marie Lejeune, University of Bristol, arrived on Montserrat yesterday to join the MVO staff. Dr Ambeh takes over as Chief Scientist and Head of MVO from Lloyd Lynch. Dr Lejeune will be working on the mapping of the dome. Mr Mick Murphy, Bristol University, arrived today for a short visit. He will be looking at some of the pyroclastic flow deposits.

The Soufriere Hills Volcano is still considered to be highly dangerous to people and property on it's eastern and upper western flanks. Visits to the evacuated zone must be kept to a minimum. The Tar River and Long Ground areas to the east and upper Fort Ghaut, Gages Village and Upper Amersham areas to the west are all extremely dangerous. All access roads to these areas remain closed and people should not enter these areas under any circumstances. If they do, they put themselves and others at direct risk of serious injury or death.

Montserrat Volcano Observatory