Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 08 June
to 16:00 09 June 1996

Volcanic activity at the Soufriere Hills volcano has been at a moderate level today. The activity is still dominated by small to moderate-sized rockfalls from the lava dome. Good visibility has enabled confirmation of significant changes to the status of the volcano over the past few days.

Generally small rockfall signals continue to dominate seismicity at the volcano. There were 54 of these events during this reporting period, almost identical to yesterday's count. The largest event was at 20:22 on 8 June. There was one hybrid event today and 3 long period earthquakes. There have again been brief periods of intermittent low-amplitude broadband tremor throughout the reporting period, recorded only on the Gages station at present.

Excellent viewing conditions today enabled observations of the dome from the ground and the helicopter. The main point of note in these observations is the switch in activity on the dome from the northeast around to the northwest. This is causing hot rock to fall directly onto the inside of the Gages Wall, rapidly filling the gap which had been at a constant 60 ft or so for the past 3 months. The gap is now less than 20 ft and if the current foci of dome growth continues, it will only be a matter of a few days before hot material will start to fall into the upper reaches of Fort Ghaut. Other observations were that vertical growth of the dome continues, with two spines now present on the western side of the summit area, and that there are a number of areas of vigorous steaming and gas production.

EDM measurements were made today on the eastern triangle between White's Yard, Long Ground and Castle Peak. Only 2 mm of movement was detected for the Castle Peak reflector since the last occupation 5 days ago; this is a significant reduction in the shortening rate since a week or so ago. Analysis of yesterday's occupation of the northern triangle shows no change in the line lengths to the Farrell's reflector.

COSPEC measurements of the SO2 gas concentration in the volcanic plume were carried out again today. The measurements are currently being processed. A flux of between 170 and 429 tonnes per day was measured yesterday - a somewhat higher level than the previous day. The range in values for gas flux for yesterday reflects the relative inaccuracy of the method - scientists would expect much larger changes in gas flux than are currently being recorded prior to any change towards major explosive activity at the volcano.

Scientists at the Montserrat Volcano Observatory have today made observations which indicate a significant increase to danger levels on the western side of the volcano. Visits to the evacuated zone should be kept to an absolute minimum. The Tar River, Long Ground and Whites areas remain extremely dangerous and other areas around Gages Village may soon become equally dangerous. People should not enter these areas under any circumstances. If they do, they put themselves at direct risk of serious injury or hideous death.

Montserrat Volcano Observatory