Volcanic activity has continued at a low level during the last 24 hours with two swarms of volcano-tectonic earthquakes and further growth of the recent extrusion; otherwise the level of seismic activity has been low.
Visual observations were limited to a short helicopter flight during which only the lower half of the new extrusion was seen. A large piece of the old Castle Peak has fallen away. A sizeable debris fan of rockfall material is accumulating at the base of the two eroded valleys near Castle Peak.
There were two swarms of volcano-tectonic earthquakes during the period, from 5:49 pm to 7:12 pm and a smaller one from 5:27 am to 6:24 am. A total of 23 earthquakes were recorded in these swarms, which were smaller than the recent swarms. Both swarms were accompanied by sequences of low level repetitive hybrid earthquakes. After the second swarm the hybrid activity was followed by a low level banded tremor that lasted for about two hours. There were also 10 hybrid earthquakes and one long period earthquake. The level of rockfall activity remained moderately low, with only 31 today.
Poor weather conditions hindered most field work today. A gravity survey was conducted on the western flanks of the volcano.
The eastern face of the dome is steep, and likely to collapse soon. Any collapse is likely to be gradual, although 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.