Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 31 July
to 16:00 01 August 1996


level of activity at the Soufriere Hills volcano during this reporting period was lower than that observed during the previous 24 hours. It was dominated by small- to moderate-sized rockfalls from the flanks of the growing lava dome.

One hundred and seventeen (117) rockfalls were recorded, with the largest occurring at 18:13 on 31 July, and 01:19, 09:03 and 11:29 on 01 August. Only the event of 11:29 produced a small ash cloud which was seen drifting to the west over the Upper Gages area. There were two episodes of small, repetitive hybrid earthquake occurrence which eventually led to low-amplitude, low-frequency, harmonic tremor. More than 215 distinct small hybrid earthquakes were recorded. There were 36 long-period earthquakes and 20 volcano-tectonic (VT) earthquakes during the reporting period. The long-period events were generally very small. The VTs were located at shallow depth beneath the crater. Intermittent low-amplitude broadband tremor was also recorded at the seismic stations closest to the crater area and may be due to increased steam emission from the crater. A slightly larger broadband signal recorded on the Gages seismic station from 03:38 to 03:50 today is typical of those associated with flash flooding in Fort Ghaut.

Visibility was generally very poor throughout the day, with the volcano covered by clouds. However, light steam emission was observed from the area where the pyroclastic flows entered the sea and also from the Tar River Valley.

EDM measurements on the eastern triangle were made today and the results show a very small shortening of 4 mm for the Whites to Castle Peak line. COSPEC measurements of the amount of SO2 in the volcanic plume were also made but the results are still awaited. No GPS measurements were made today.

The ashfall due to yesterday's pyroclastic flow was not completely washed away by overnight rains and continues to make driving hazardous. Please be careful when driving and remember to wear dust masks while cleaning ash in the home or outside.

Mr. Rod Stewart of the BGS left Montserrat yesterday.

While the current phase of activity at the Soufriere Hills volcano continues, hazards in some areas of the evacuated zone have increased significantly. The Tar River Valley and surrounding areas are extremely hazardous, and should not be entered under any circumstances. Visits to the evacuated zone should generally be kept to a minimum. We urge individuals who continue to ignore this advice to think very seriously before making trips to these highly hazardous zones.

Montserrat Volcano Observatory