Activity at the Soufriere Hills volcano during this reporting period has remained at a relatively elevated level compared with early in the week. No observations of possible new surface extrusions have been possible.
Eleven rockfalls were recorded during the reporting period. Thirty three volcano-tectonic earthquakes occurred during the day; these VT's are somewhat transitional with hybrid events, and are at a slightly higher level than during the previous reporting period. Nine hybrid and three long-period events were also recorded by the network. Broadband tremor of variable but generally low amplitude was recorded intermittently on the Gages seismometer. Two regional earthquakes were recorded today, at 10:37 and 10:54.
Visibility was moderate all day, although the top of the dome and the interior of the scar were obscured by cloud and steam. Some mapping of the new deposits in the Tar River valley and on the pyroclastic flow delta was undertaken from the helicopter; this will help with estimating the volume of rock involved in the collapse and explosion of last week.
Results from yesterday's EDM measurements were calculated today. The line between lower and upper Amersham showed a lengthening of 4.8 cm between 20 and 26 September; although this line has not shown any consistent changes over the past year, this measurement marks one of the sharpest changes yet recorded. The Amersham to Chances Peak steps line showed no change.
MVO scientists expect that rockfalls and possibly pyroclastic flows will occur during the next few days as the unstable sides of the new scar feature at English's Crater stabilise. All indications are that the rockfalls and pyroclastic flows will be confined to the Tar River valley area. Dust masks should be worn at all times in ashy environments, which may persist for some time as ash dries out and blows around. Drivers should exercise caution and consideration for other road users, especially when driving through areas still affected by ash or gravel.
Individuals put themselves in extreme danger if they venture beyond the Long Ground area into the Tar River valley. All individuals passing checkpoints in whatever part of the island are reminded that they are entering areas which may become unsafe very quickly, and everyone should be on maximum alert in all of these areas. All residents of southern Montserrat are asked to once again ensure that they are familiar with evacuation procedures.