Activity at the volcano continues at a moderate level. Between 16:00 yesterday and 16:00 today there were 12 hybrid earthquakes, 3 long period earthquakes and 45 rockfall signals. Two of the hybrids and one of the long period earthquakes preceded rockfalls. The rockfalls and hybrids tended to occur in short periods of higher activity approximately 6 to 8 hours apart, although the peaks in activity are not well defined.
Cloud has again covered the top of the volcano all day and so there have been no good views of the crater formed by the Boxing Day collapse. However, the heavy rain overnight meant that the ash being blown from the new deposits in the south of the island was minimised and good views of the deposit were possible this morning. Observations confirmed that the areas of Trials and Fairfield had both been badly affected by the Boxing Day event. In Trials, most buildings have been damaged. Roofs have collapsed and there is some fire damage but most structures are still standing. In Fairfield, the roofs of some houses have collapsed as a result of heavy ash fall, but the pyroclastic surge probably did not reach this far, as there is apparently no evidence for fire damage.
A short visit was possible to the White River pyroclastic fan near the old quarry buildings to measure temperatures and thicknesses of the new deposit and collect samples. The flow front of the debris avalanche is about 30 m high, and the pyroclastic surge deposit is between 50 and 70 cm thick here. Temperatures up to 228 degrees centigrade were recorded at 30 cm depth in the pyroclastic flow deposit. Due to the stormy conditions, a large amount of burnt wood has been washed ashore. These include logs up to 4 m long and 45 cm in diameter.
A helicopter GPS survey was undertaken of the new deposits in the lower reaches of the White River valley, and preliminary analysis of these data show that the pyroclastic fan does not appear to have been extended significantly into the sea away from the coast, but is probably twice as wide along the coast, with a total width of 1.5 km. The bathymetry at the mouth of the White River valley slopes off quickly into deep water, and so much material may have slumped down off this shelf into deeper water.
Air quality at all monitoring stations across the island is good today.
People should remain alert and listen to Radio Montserrat for further information.
Report for the period 6 pm 3 January to 6 pm 4 January 1998