Activity at the Soufriere Hills volcano during at the reporting period has continued at a very low level. Rockfalls were the only seismic signals recorded by stations around the volcano today.
Fifty-six small rockfall signals were recorded during the reporting period. The largest event occurred at 11:25 on 20 September. A single mudflow signal which lasted for about 40 minutes began on the Gages seismic station at 06:00 on 20 September. This may have been caused by the remobilization of thick ash deposits in Fort Ghaut left behind from last Tuesday's activity. A few signals which are the same as those reported in the early morning update as high amplitude hybrid events were correlated with rockfalls by scientist working in the field today. No other signals recorded by seismic stations during the reporting period.
Visibility was generally poor for most of the day but some views were obtained of the lower parts of the new u-shaped scar feature which has developed at English's Crater. Several small rockfalls were observed to occur from the steep sided walls of the feature, particularly toward its northern and western sides. These rockfalls generated small ash clouds and deposited new debris at the base and open end of the u-shaped feature. Observations by a field team in the Tar River area indicate that the topography of the valley has been markedly smoothed due to deposition of a large amount of ash in the base of the valley. Temperature probes into the fresh pyroclastic surge deposits along the road to the Tar River estate house gave results of up to 97oC at 45 cm depth.
EDM measurements were carried out today on the line lengths from Amersham to Amersham and from Amersham to Chances Peak. There were no changes in line lengths since this station was last occupied on 23 August. The results from the GPS survey which was completed yesterday are still being checked and would be available tomorrow.
MVO scientists are expecting more rockfalls and possibly pyroclastic flows to occur during the next few days as the unstable sides of the new scar feature at English's Crater stabilizes. All indications are that the rockfalls and pyroclastic flows will be confined to the Tar River valley area. Areas affected by associated ashfalls will depend on the direction and strength of the wind at the time. Dust masks should be worn at all times in ashy environments, and drivers should exercise caution and consideration for other road users.
The extensive damage which occurred in the Long Ground area on Tuesday night further demonstrates the extreme danger which individuals subject themselves to if they venture into these areas. The Tar River and Long Ground areas are now extremely hazardous and we urge individuals who persist in ignoring this advice to think very seriously before making trips to these potentially deadly zones.