Activity over the past 24 hours has been dominated by rockfalls and small pyroclastic flows from the active area in the southern part of the dome. Low cloud has again hampered observations.
The broadband seismic network recorded a total of 86 rockfall signals during the past 24 hours, a slight reduction from yesterday. The rockfalls have again been occurring from the south-western flank of the dome, shedding material into the upper part of the White River valley as well as the upper part of the Tar River valley. There were 25 long-period earthquakes, of which 20 triggered rockfalls. One volcano-tectonic and one hybrid earthquake were also recorded today.
Three regional earthquakes were recorded during yesterday evening. The largest, at 9:44 pm, was a magnitude 5.2 event at shallow depth about 20 km to the southwest of Tobago. An earlier event, at 6:39 pm, had a magnitude of 4.5 and was located in a similar place. Both of these earthquakes were felt in Tobago and northern Trinidad. A third regional event, at 9:11 pm, was located somewhere near Barbuda, about 100 km to the north of Montserrat, but was only of magnitude 3 to 3.5.
Visibility has been poor all day and no views of the dome have been possible. Accumulation of rockfall debris was noted in the upper part of the Tar River valley adjacent to the southern crater wall, consistent with the increasing number of rockfalls in this direction.
Preliminary EDM measurements were undertaken this afternoon on the eastern network, where a new reflector will be installed in the Hermitage area during the coming week. A GPS receiver is currently being set up at Farrell's and the position of the pin at that location will be measured relative to Harris Lookout overnight. The crack on the eastern flank of the Galway's Wall was measured yesterday - the results show some opening of the crack since the last measurements, and this is the first time this crack has shown any significant movement since first measured in late March.
Water and ash samples and sulphur dioxide diffusion tubes were all collected today and will be analysed over the next few days.
The volcano remains dangerous, and only essential visits should be made to the evacuated zone. People should wear masks when in the ashy areas. The Tar River and White River valleys are extremely dangerous, and should not be entered under any circumstances.