Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 24 August
to 16:00 25 August 1996

Activity at the Soufriere Hills volcano during this reporting period continued at a slightly higher level than that observed during the previous period. Its nature is still dominated by small- to moderate-sized rockfalls from the eastern flank of the lava dome.

Sixty two (62) small- to moderate-sized rockfalls, 3 small volcano-tectonic and 4 small regional earthquakes were recorded. The largest rockfalls occurred at 20:07 on 24 August and 00:57, 03:20, 05:03 and 08:47 on 25 August and were associated with very small ash clouds. Most of the rockfalls were embedded in two periods of slightly higher amplitude broadband tremor from 23:40 on 24 August to 03:00 on 25 August and 08:30 to 11:00 today. Several episodes of low- to moderate-amplitude broadband tremor were recorded at the stations closest to the Crater, especially the Gages seismic station, throughout the reporting period. The increased tremor was probably due to increased steam emission from the Crater.

Visibility today was very good. Vigorous emission of ashy steam from the top part of the collapse structure was observed. Several other areas of the dome were also steaming albeit less vigorously. Rockfalls were occurring from the eastern flank of the dome and being channelled through the eroded gully which is rapidly filling up. The remnant of the new dome which was extruded in the void left by the collapses of 29 and 31 July looks quite unstable.

COSPEC measurements were made today but the data is still being processed. EDM measurements were made on the eastern and southern triangles today. The results for the eastern triangle show shortenings of 1.4 cm and 7mm compared to results of 18 August for the Whites to Castle Peak and Long Ground to Castle Peak lines respectively. The results for the southern triangle indicate shortenings of 4 mm and 5mm compared to results of 19 August for the Galways to Chances Peak and Ogarras to Chances Peak lines respectively.

Further rockfalls and pyroclastic flows will occur but all indications are that these will be confined to the Tar River Valley area. However, areas affected by associated ashfalls will obviously depend on the direction and strength of the wind at the time. People in areas affected by ash falls should exercise great care when driving. Dust masks should be worn in ashy environments.

The Tar River Valley and surrounding areas are now extremely hazardous, and should not be entered under any circumstances. We urge individuals who continue to ignore this advice to think very seriously before making trips to these highly hazardous zones.

Montserrat Volcano Observatory