Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 28 May
to 16:00 29 May 1996

Volcanic activity at the Soufriere Hills volcano has been dominated by continued rock avalanches from the growing lava dome which have produced ash clouds and small pyroclastic flows in the upper Tar River valley.

Seismicity continue to be dominated by small- to moderate-sized rockfall signals. The level of seismicity has been moderate with the larger signals correlated with ash plumes which attained heights of up to 3500 ft and with small pyroclastic flows into the upper Tar River valley. The largest signals occurred at 20:30 and 20:43 on 28 May and 02:48, 03:44 and 15:29 on 29 May. A slight change in the wind direction today caused light ashfall to affect areas to the west and northwest of the volcano. Eight long period earthquakes and one hybrid event was also recorded by the seismic network. Low-amplitude broadband tremor has generally been intermittent but there were discrete periods from 20:00 on 28 May to 04:40 on 29 May when tremor was continuous.

No EDM or GPS measurements were made today due to heavy rainfall and technical problems respectively. Replacements for faulty GPS equipment was received today and an attempt would be made to restart measurements during the next few days..

Inclement weather throughout the day prevented COSPEC and FTIR measurements of gas concentrations in the volcanic plume. The results of gas measurements using the FTIR method yesterday indicate that HCL (40 parts per billion) and SO2 concentrations, are well below levels of concern for human habitation.

Overcast conditions and intermittent light rainfall did not allow clear views of the volcano for most of the day. During the late afternoon conditions improved sufficiently to allow visual observations to be made from the ground and also from the helicopter. No major changes in the shape or size of the dome were noted, although semi-continuous rock falls continue to occur from the northeastern and eastern flanks of the dome. Vigorous steaming continue to occur from the moat area and from the southwestern and western parts of the dome. Incandescent material was observed from several areas in the east and northeast of the dome. Several small pyroclastic flows were observed from the top parts of the dome. These flowed down the eastern flank of the dome and into the upper parts of the Tar River valley. None of these flows reached further than the Tar River Soufriere.

The present level of activity at the Soufriere Hills Volcano continues to cause concern to the scientists. The MVO urges 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