Montserrat Volcano Observatory

Daily Report
Report for the period 5 p.m. 25 October
to 5 p.m. 26 October 1998

The activity at the volcano has been at a higher level during the period of this report. There were 21 rockfall signals, 8 volcano-tectonic and 6 hybrid events during the 24 hours since 4 p.m. yesterday afternoon.

At 12:51 a.m. this morning, a small collapse of the dome occurred. The seismic signal lasted for about 12 minutes and was followed by an extended period of volcanic tremor. Reports were received of thunder from the resultant ash cloud, and there was subsequent wet ash fall as far north as St. Peters. Information received from satellite images suggested that the ash cloud reached to between 20,000 and 25,000 feet high.

Observations during the early hours of the morning from Salem suggested that there were two ash cloud lobes: one to the south of Belham Valley and one over the Salem-Old Towne area. Measurements of ash thicknesses this afternoon showed that deepest measured ash fall was at Richmond Hill where 25 mm or about one inch had accumulated. About 4 mm had fallen in Old Towne. The ash was almost entirely fine grained, with some clumps of fine material also occurring.

During an observation flight later in the morning, new deposits were seen in the Tar River area. Steaming could be seen at the edge of the delta, indicating that the pyroclastic flows travelled into the sea. The flows also reached as far north as the Tar River Estate House. On the south-west side of the volcano down the White River, a thin deposit of ash from pyroclastic flows could be seen as far as about 700 m from the old coastline at O'Garra's. It is uncertain when pyroclastic flows travelled in this direction. The dome could not be seen due to low cloud, and so it is not clear how much material collapsed from the dome and from which areas the flows originated.

Measurements of the gas composition of the plume have been done over the last 3 days by a team from Cambridge University. Results should be available later in the week.

Residents of Montserrat are advised to keep listening to ZJB Radio Montserrat for information relating to any further developments in the state of the volcano.

Montserrat Volcano Observatory