Major pyroclastic flow activity in the Tar River valley started at 5:06 pm tonight. These pyroclastic flows were caused by collapses from the eastern side of the December 11 dome. The flows were chanelled to the north of Castle Peak, down the Hot River valley and travelled almost to the sea.
Activity had been at a relatively low level during the day, with some small pyroclastic flows around 8 am which travelled approximately 1 km from the dome. The activity built up rapidly from 5:06 pm to a peak just before 6 pm. The pyroclastic flows generated ash clouds which rose to around 10,000 ft above sea level, and were carried to the southwest by the light winds.
Observations from the airport during the major pyroclastic activity suggested that fresh lava was being supplied to the dome as quickly as it was being lost in pyroclastic flows.
Due to the danger that this pyroclastic flow activity might lead to a vertical explosive eruption, similar to the activity of September 17, the scientists have recommended that the alert stage is increased to Red.