Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 18 April
to 16:00 19 April 1996

The level of activity at the Soufriere Hills volcano has decreased slightly over the last 24 hours, with fewer earthquakes and less dome activity. However, the volcano remains in a state of extreme unrest that could escalate at any time.

The number of hybrid earthquakes has decreased since 10 pm yesterday (Thursday), and they are now occurring at a rate of about one earthquake every two minutes. The size of the earthquakes has remained about the same. Three periods of broadband tremor, each lasting for about 2 hours have been recorded. A moderately sized explosion occurred at 19:27 last night, and was the largest explosive signal recorded in the last four days. Several rockfalls from the dome were also recorded.

Deformation measurements were carried out on the eastern side of the volcano, and the lengths of nine lines were determined using the GPS equipment. This is the first time that the eastern network has been fully remeasured, and the results will be available tomorrow. The seven lines of the western network were remeasured yesterday. The results were processed last night and all the line lengths had changed by less than one centimetre over the preceding three days. These changes are within the error of the technique. EDM measurements were made of the eastern triangle, but the results are still being processed.

The cloud conditions have been variable today, and some visual observations of the crater area have been possible. This morning, measurements of the new spine that was first seen yesterday showed that there had been no major changes overnight. The current height of the spine is 2940 ft. Another smaller spine in the southeast part of the dome was observed this morning. It is about 2/3 of the height of the main spine. The height of the dome measured today from the Observatory was 2840 ft, indicating no change in height since yesterday morning. During the day, scientists in the east heard near-continuous rockfalls, but there was no visible activity on the eastern side of the dome. It is possible that the focus of dome activity has shifted to the western crater.

Dr Joe Devine arrived in Montserrat last night to rejoin the scientific team. He will be on island for ten days to help with deformation fieldwork and make visual observations. Dr Laurence Donelly from the British Geological Survey arrived this morning for a six week visit.

Despite the slight decrease in the activity over the last 24 hours, the volcano remains extremely active, with continued dome growth at a high rate. The scientific team remains highly concerned by the current activity, and urge that visits to the evacuated zone are kept to a minimum. The Tar River, Long Ground and Whites areas are extremely dangerous, and should not be entered under any circumstances.

Montserrat Volcano Observatory