Montserrat Volcano Observatory

Daily Report
Report for the period 5 p.m. 3 July
to 5 p.m. 4 July 1998

The volcanic activity was at an elevated level today following the dome collapse of yesterday morning.

Over the last 24 hours, 39 rockfall signals and 1 volcano-tectonic earthquake were recorded by the seismic network. A brief period of low amplitude tremor was recorded on the Lees Yard seismic station at about midnight and, as this coincided with heavy rain and thunder, this was thought to be due to a small mudflow.

Work today has started to try to understand yesterday's events. The extent of the new deposits is being mapped, and some samples have been collected from the Tar River delta. The houses in the southern end of Long Ground appear to have been scorched by hot ash, but not severely damaged. The samples from the delta include a few pumice clasts as well as abundant dome rock fragments. The deposits were still extremely hot and very fluidised. There are still substantial amounts of steaming originating from the edge of the delta. There is a lot of new material in lower two thirds of the Tar River valley. The summit of the dome was not clear today, but a line of steam vents could be seen in the base of the scar formed by the dome collapse.

Observations at the Belham Bridge confirmed that the mudflow at midday yesterday has added more material under the bridge so that there is only a maximum of 35 cm clearance between the top of the stream bed and the bridge. Average clearance under the northern section of the bridge is 10 cm. The southern section of the bridge is almost entirely blocked with debris, and is piled up to about 50 cm below the level of the road. There were also rocks up to 30 cm in diameter on the bridge.

Dust levels at monitoring sites in Salem and Old Towne were at alert level, very high at a site in Woodlands, and low at MVO in Mongo Hill today.

Following the activity yesterday, further explosions and pyroclastic flows are possible down all flanks of the volcano. Residents should continue listening to Radio Montserrat in case there are more sudden developments in the state of the volcano.

Montserrat Volcano Observatory