The level of volcanic activity increased between 5 pm and 6 pm last night, with a series of large pyroclastic flows down the Tar River valley. These pyroclastic flows were caused by collapses from the eastern side of the December 11 dome. The flows were channelled to the south of Castle Peak, down the Hot River valley and travelled almost to the sea.
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 the pyroclastic flow activity might lead to a vertical explosive eruption, similar to the activity of 17 September, the scientists recommended that the alert stage was changed to Red.
Since 9 pm last night, the level of activity has been lower, with only a few moderate-sized rockfalls recorded.