A slight increase in volcanic activity has been observed during the last 24 hours. The recent pattern of two volcano-tectonic earthquake swarms continued but the level of rockfalls and hybrid earthquakes was higher. From visual observations it appeared that the focus of growth remained in the south-eastern section of English's Crater but there was also evidence that the Galways section of the crater wall is being further loaded.
Fairly good views of the new dome growth were possible from the helicopter this morning. It was clear that the in-filling of the scar left by January 20th collapse had continued overnight. The growth extended above the scar rim up to the height of the older structure of the October 1 dome. The chute (valley) leading out of the scar had become partially filled with rockfall debris indicating that the whole structure was getting very close to the state for the next collapse.
A total of 53 volcano-tectonic earthquakes were recorded, in two swarms between 12:00 am and 3:30 am, and 12:53 pm and 14:39 pm. All of the earthquakes that could be located were in the same place as previous swarms- that is, at shallow depths beneath the volcano. There were also 48 rockfall signals, 21 hybrid earthquakes and 7 long-period earthquakes.
There have been further landslides from the upper part of the outside of Galway's Wall. Some sections of the wall is now being over-topped by fragments from the dome. For safety reasons the cracks at Chances Peak were not measured today. The scientific team will monitor the area around the Galway's Wall closely in the next few days, to check for signs of further deformation.
EDM measurements were made from Amersham to the reflector on Chances Steps. The results are not yet ready for publication. The results of yesterday's survey of the dome indicates that about 2 million cubic meters of lava was lost in the pyroclastic flow on January 20. The average rate of growth between the six day period from 20 - 26 January 1996 is 3.4 cubic meters per second.
As the new extrusion in the south-east of the crater continues to grow, it is likely that it will collapse and cause further pyroclastic flows in the next few days. Although the dome is likely to collapse gradually, a larger collapse cannot be ruled out. An explosion similar to that of September 1996 could result in the event of a major collapse. It is however expected that there would be several hours of high level pyroclastic flow activity before any explosion. Zone E, which includes Cork Hill and the airport, remains safe.