Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 17 August
to 16:00 18 August 1996

Activity at the Soufriere Hills volcano during this reporting period was again at about the same level as that observed during the past several days and was also similar in nature. It was mainly dominated by small- to moderate-sized rockfalls and a few small pyroclastic flows from the eastern flank of the growing lava dome.

Seventy (70) rockfalls, 21 hybrid, 4 long-period and 5 volcano-tectonic earthquakes were recorded during this reporting period. Starting around 13:00 up to the end of this reporting period today, the occurrence of rockfalls was near-continuous. The largest rockfalls occurred at 20:46 on 17 August and 10:37, 13:23, 14:54, 15:01, 15:14 and 15:18 on 18 August. All of these large rockfalls led to small pyroclastic flows which were confined within the the Tar River Valley, with the flow for the event of 15:01 travelling the furthest from the dome, to as far as the Tar River Estate house. The small- to moderate-sized ash clouds produced were blown on the wind towards the west, resulting in small ashfalls in Upper Gages, Plymouth and environs. The ash cloud for the 15:01 event reached a height of about 6,000 ft above sea level. The volcano-tectonic earthquakes were located at depths of less than 2 km beneath English's crater. Several episodes of intermittent low-amplitude broadband tremor were also recorded at the stations closest to the Crater.

Visibility was good during parts of the day, with vigorous steaming occurring from most of the dome. Most of the observed rockfalls were from the eastern part of the dome.

EDM measurements were made today but the data is still b eing processed.

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