Montserrat Volcano Observatory

Weekly Report
Report for the period 5 p.m. 26 March 1999
to 5 p.m. 2 April 1999

Activity at the volcano has remained at a similar level this week to the previous few months.

A total of 78 rockfall signals and 13 volcano-tectonic earthquakes were recorded over the last week.

There were a total of 10 ash venting or small explosive events last week. The two largest events occurred on 26 March at 18:43 and on 1 April at 00:50. The explosive event on 26 March produced an ash cloud with associated lightning that reached to approximately 20,000 feet, and gritty ash fell as far north as Woodlands. No significant pyroclastic flows occurred with this event. The event on 1 April produced a plume again reaching about 20,000 feet, but the ash cloud travelled to the west at low levels and to the north-east at higher levels. Observations later in the day revealed that a pyroclastic flow had travelled down the Tar River onto the delta, but only minor deposits could be seen in the White River and Gages areas. Samples were later taken from the deposit on the Tar River delta, and temperatures of up to 150 degrees centigrade were measured at 30 cm depth in the new material. One ash venting episode, still ongoing at the time of reporting, produced a dark ash cloud that travelled to the west.

An occupation of the Long Ground network was completed this week, but no significant movement can yet be discerned.

A new GPS site on the south side of Tar River was occupied for the first time this week.

Residents of Montserrat are advised to keep listening to ZJB Radio Montserrat for information in case of any changes in the state of the volcano.

Montserrat Volcano Observatory