Continued growth of the October 1 dome in the last 24 hours has resulted in further rockfalls and pyroclastic flows. Several moderate-sized ash columns occurred, and were blown to the southwest. The level of pyroclastic flow activity has increased slightly since yesterday. A major collapse of the dome could happen during the next few days, and there is a chance that this will trigger an explosion similar to that of 17/18 September.
Visibility has been quite poor today, and no good views have been possible of the dome. Observations late last night showed that the north and eastern faces of the October 1 dome are active, and several rockfalls were observed. During today, a few pyroclastic flows were observed in the chute above Castle Peak, and these travelled about one kilometre from the dome.
The seismic activity continues to be dominated by rockfalls and pyroclastic flows. A total of 121 rockfall were recorded today, an increase on the 95 recorded yesterday. The size of the largest pyroclastic flow signals has increased slightly since yesterday. There were few other seismic signals today, comprising one hybrid, two volcano-tectonic and two long-period earthquakes.
GPS and gravity measurements were made today at stations on the western side of the volcano, including sites in the Galway's region which were measured for the first time since July 1996.
Two runs were made with the correlation spectrometer this morning along the western side of the volcano, to measure the amount of sulphur dioxide gas coming from the volcano. The results are still to be processed, but showed a peak in the amount of sulphur dioxide just after a pyroclastic flow at 10:59 am.
Calculations were completed today of the volume of the material added to the October 1 dome between December 25 and January 5. 4.6 million cubic metres of material was extruded during this period, at a rate of 4.4 cubic metres per second.