No earthquakes have been located during this period. However, a number of long-period events were recorded on most of the seismometers throughout the period; such earthquakes are very difficult to locate accurately due to their character. Three of these long-period earthquakes were associated with small ash eruptions, occurring at 07:08, 07:23 and 15:19 on 20 December. Ash from these eruptions was blown towards the north and a small density current of ash was seen flowing down the upper flanks of the volcano in the Farrells area from the first of these events. The regular long-period earthquakes recorded at the Gages seismic station recently have continued, although their amplitude is very small. Flash floods were recorded by the Gages seismometer between 17:00 and 19:00 last evening.
Measurements were made along all of the EDM lines today thanks to the excellent visibility. The results from these surveys are still being processed, although movements along all lines appear to be within the error of the measurements. Results from yesterday's surveys showed a lengthening of 4 cm on the line from Amersham to Gages Wall but no significant changes on other lines measured. GPS measurements were made at St George's Hill, Reid's Hill and Harris' Lookout. The line between Harris' Lookout and Reids Hill shortened by 1.8 cm between yesterday and today, somewhat reversing the changes reported yesterday. However, the total change recorded over the two days is still larger than any seen previously by this technique.
Visual observations were made from Chance's Peak, White's Yard/Long Ground and from the helicopter today thanks to excellent visibility. Early this morning, Police Officers at the airport reported seeing glowing material falling from the Castle Peak area. The debris from this rock fall was seen at first light from the helicopter and it covered only a small area on Castle Peak Dome; it did not move into the Tar River valley as was reported earlier today. The large spine in the central part of the new lava dome continues to grow in height; it grew an estimated 20 m between 17 and 20 December and now stands at a height of about 40 m above the surrounding material. Observers from Chance's Peak reported that the top of the new spine was almost at the same height as Castle Peak.