Montserrat Volcano Observatory

Daily Report
Report for the period 5 p.m. 12 January 1999
to 5 p.m. 13 January 1999

Activity at the Soufriere Hills volcano was heightened during the past twenty four hours. There was a violent eruption at 6.30 am on Wednesday morning. The initial signal lasted for 4 minutes then was followed by a second pulse 5 minutes later. Numerous reports of rumbling sounds were received and a pressure wave was recorded on the instruments which measure atmospheric conditions..

The eruption generated a vertical eruption column which rose very rapidly to 20,000 feet above sea level. There was much thunder and lightning associated with the eruption cloud which had a base that was very dark with ash,topped by a cleaner, pale upper plume.

In response to a strong easterly wind which prevailed at the time of the eruption, the cloud drifted almost due west, shedding ash only on that narrow sector from Cork Hill to Plymouth, including Garibaldi Hill and St. Georges Hill. There was no ash fall on any area in the occupied zone, north of the Belham Valley. At 8.30 am reports from aircraft in the area indicated that the cloud had drifted twenty miles west of Montserrat at a height of approximately 15-20000 feet.

The eruption generated a pyroclastic flow which went down the Tar River valley to reach the sea where steam clouds were created on contact with the water.This flow was approximately two thirds of the volume of the largest event of November last which also traversed the deltaic fan at Tar River. Some very small overspill pyroclastic deposits were observed in the uppermost chutes on the dome, high up above the Galways area. The Gages/Fort Ghaut sector was unaffected by any flow deposit.

The eruption concluded with a period of volcanic tremor lasting several minutes along with vigorous ash venting from the fumaroles over the Tar River sector.

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