The level of volcanic activity at the Soufriere Hills volcano has been slightly lower than yesterday, with no large pyroclastic flows. There were two earthquake swarms followed by a periods of volcanic tremor. The Galway's Wall has crumbled further since it was last observed, and dome material has eroded a deep notch in the top of the wall.
A total of 44 volcano tectonic and 33 hybrid earthquakes were recorded since 4:00 pm yesterday. There were also 38 rockfall signals. Most of the earthquakes occurred in two swarms, from 5:20 pm to 8:20 pm, and from 7:30 am to 10:10 am. Both swarms were followed by periods of tremor, from 8:40 pm to 10:20 pm and 10:30 am to 12:15 pm. The second episode was of higher amplitude than the recent tremor, and was associated with some pyroclastic flows.
The pyroclastic flows reached to where the road used to cross the Tar River valley, and resulted in moderate ash clouds that were blown to the west over Plymouth. No pyroclastic flows or ash were observed during the first episode of tremor.
Observations of the dome were made from the helicopter. The new extrusion has extended further down-slope, and has a blocky front, and more material has fallen from the face to the base of the dome.
The top of Galway's Wall has been altered significantly in recent days. A deep slot has been cut through the top of the wall along a line of weakness, and material from the pre-September dome has fallen through the slot. This material forms a fresh grey deposit that lies on top of some of the debris from the earlier landslides from the wall. A smaller slot has been cut through the eastern end of the wall, and fresh landslides were noted from the Chances Peak end. The central portion of the wall is now divided into solid towers separated by deep slots.
A GPS campaign was undertaken today at the Tar River, Windy Hill, Whites and Farrells stations.
The eastern face of the dome is steep, and likely to undergo further collapse soon. Any collapses are likely to be gradual, and follow the recent pattern. However, a larger collapse cannot be ruled out. An explosion similar to that of September 1996 could result in the event of a major collapse which lasted for several hours. Zone E, which includes Cork Hill and the airport, remains safe. The Tar River Valley and the upper Galway's area are very dangerous.