Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 15 May
to 16:00 16 May 1997
The current alert level is AMBER

The last 24 hours has been characterised by an increase in pyroclastic flow activity in the Tar River Valley and further degradation of the north-east flank of the dome. Excellent views of the dome were possible for a short time, and a large new spine was seen at the top of the dome.

A moderate pyroclastic flow occurred in the Tar River valley last night. Last night's flow was from the eastern face of the dome, and created a scar to the north of the scar left by the flow on Tuesday morning (13 May). The flow lasted for a longer time than Tuesday's flow, but it was not of such high intensity, and both flows excavated a similar amount of material from the dome. :Last night's flow followed a path to the north of the Tar River valley, and reached to the old coastline, just at the top of the delta.

The event began at 8:40 pm, with a continuous low-amplitude seismic signal which gradually increased in intensity. It reached a maximum at about 9:20 pm, and declined thereafter, with the activity ceasing at 9:50 pm.

No observations of the flow were possible, but MVO observers at Harris' Lookout saw the ash cloud, and some glowing from cracks in the dome. The ash was carried to the west by the wind. The observers at Harris also heard intermittent roaring sounds, which are thought to be due to vigorous steam venting from the dome.

The pyroclastic flow activity continued today, with moderate flows in the Tar River valley at 7:15 am and 3:10 pm, and there were many smaller flows. The ash from these flows has been carried to the west and north-west. A total of 42 rockfall signals were recorded, slightly less than yesterday, and there were also 39 small hybrid earthquakes. The number of long-period earthquakes remains much lower than the last few weeks, with only 10 recorded.

Views of the whole dome were possible from the MVO and the eastern side during a brief clear period this afternoon. The main development is a large new spine which has grown at the summit of the dome; a small spine was seen in this area yesterday morning, but most of the new spine has grown since then. Further erosion has occurred on the north-eastern side of the dome, and many blocks of lava have piled up against the crater rim between Hermitage and Farrells.

In the clear period, attempts were made to sight the a new EDM reflector at Farrells, but the operation was curtailed by more low cloud.

The recent activity and spine growth shows that the volcano remains active and dangerous. The dome is approaching the limits of stability and therefore further pyroclastic flows with attendant ash clouds will occur in the next few days. Only essential visits should be made to the evacuated zone, and ash masks should be worn when in the ashy areas. The Tar River and White River valleys are extremely dangerous, as pyroclastic flows can travel down these valleys with no warning. Zone A should not be entered under any circumstances.

Montserrat Volcano Observatory