Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 22 December
to 6 pm 23 December 1997

Volcanic activity continued at a similar level today with rockfalls being the dominant seismic signal. The broad band system triggered 39 hybrid earthquakes, 29 LP earthquakes and 50 rock-falls today.

There were good views of the dome today which continues to grow freely in the southern sector. The dome has grown significantly in height since the last good observations on 15 December. Photographs were taken which will enable the new height to be estimated and allow some new estimates of growth rate. The dome has changed from a relatively flat top to a steep-sided cone with several large spines near the summit and a major new spine towards the west adjacent to Chances Peak. The upper parts of the dome has been eroded into gullies by rockfall activity and several minor rockfalls were observed during the observation period. The north-eastern parts of the dome are generating a strong white steam plume and volcanic gas and fine ash are continually emerging from the active part of the dome. A prominent gully was observed on the eastern flank and some new rockfalls and pyroclastic flows were observed extending several hundred metres into the Tar River Valley. The observations confirm that the dome is actively growing over a wide area and larger pyroclastic flows could be generated down any of the major valleys, but Gages, the White River and Tar River are currently the most susceptible.

Air quality at all monitoring stations across the island is good today.

Although activity is mainly focused in the southern central part of the volcano, the area of growth on the dome can change very quickly. Growth activity appears now to be backing up behind the major build-up of material in Galways, and a renewal of rockfalls or pyroclastic flows down Gages or Tar River would not be a surprise in the near future.

Venus Bass returned from her holiday to MVO work and Mr Thomas Christopher returned from University in Jamaica to help with the monitoring work over the holidays.

Montserrat Volcano Observatory