Growth and disintegration of the October 1 dome continues, resulting in many rockfalls and pyroclastic flows. The level of activity has increased markedly overnight, with three periods of intense pyroclastic flow activity since 4 pm yesterday.
Cloud was high on the volcano at dusk yesterday evening and again this morning. Intense glowing and frequent pyroclastic flow generation was noted yesterday afternoon between about 4 and 6 pm, with activity concentrated in the area behind Castle Peak, which itself is being eroded away. This same pattern has been noted this morning, with a period of intense pyroclastic flow activity starting at about 5:30 this morning; this period is continuing and there is currently ash production at a relatively high rate. All ash is being blown west of the volcano and neither ash or pyroclastic flows are currently affecting areas to the east and north except in the area of the Tar River valley, which is extremely dangerous at present.
The seismic activity overnight has been dominated by signals generated by rockfalls and pyroclastic flows. Some hybrid events have also been recorded; these are as usual occurring beneath the crater at shallow depths.
A technical problem with the helicopter prevented any flying yesterday but it is hoped that the problem will be fixed during today.
The increasing rate of pyroclastic flow activity suggests that the dome is becoming more unstable each day and that a collapse of its eastern and northeastern flanks could start at any time. A collapse of the dome would produce pyroclastic flows in the Tar River valley and heavy ash to the west of the volcano. Should the collapse be very large, then an explosive eruption is possible, in the same way that it followed a major dome collapse on September 17/18.