Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 11 October
to 4 pm 12 October 1997

There have been two explosive eruptions during the reporting period, in total there have now been 48 explosions since September 22nd

An explosion took place at 17:57 yesterday. The ash cloud rapidly rose to about 20,000ft and was reported by several observers to be broader than usual. Pyroclastic flows generated during the eruption travelled down Gages Valley as far as Lovers Lane, down Tyers Ghaut, and down both Tar River Valley and Tuitt's Ghaut almost as far as the sea. Low ash clouds passed north west over Salem and Olveston and the upper parts of the cloud drifted to the north east affecting most of the north of the island. Incandescent blocks and a glowing cloud could be clearly seen from Antigua.

The second explosion occurred at 7:55 this morning. Pyroclastic flows travelled down Gages Valley as far as Gages village and down Tuitt's Ghaut as far as Harris. The ash cloud reached over 12,000ft, the upper parts drifted slowly to the north. This event was smaller than the previous one and the ash cloud was reported to have been very steam rich. Nevertheless, the north of the island was again affected by ash fall and muddy rain.

As usual, tremor continued for some time after both explosive events. There was a small long period earthquake prior to the first explosion, this was the only one recorded during this reporting period. Two large hybrid earthquakes also occurred soon after the first explosion marking the end of the hybrid swarm which continued throughout most of yesterday. Overnight and today the level of seismic activity has been low. Only one volcano-tectonic earthquake and 5 significant rockfalls were recorded.

A dome volume survey is underway using theodolite data and the static photo method. The volume of the dome has been dramatically reduced by the dome collapse on 21st September and the continuing explosions. During the current explosive style of activity dome growth is not expected. New material rising beneath the dome is blasted out of the crater by the regular explosions and the only addition to the dome is a low wall of ash and pumice on the open north east side of the crater.

More explosions are expected and it is always possible that the next one will go on for longer than those previously experienced. If an explosion were considerably longer lasting than those already seen then it would be followed by bigger pyroclastic flows and surges. Material would then be expected to get further down Tyer's Ghaut and into the Belham River and all residents still remaining in Friths, Old Towne and Salem are urged to move out as soon as possible.

After explosions, fallout can occur anywhere on the island and hard hats or other suitable protection should be worn outside, if possible stay indoors until the fallout is over. Driving during ash or pumice fall is dangerous and should be avoided if possible. When driving on ashy roads drive slowly, particularly near pedestrians and allow plenty of time for your journey. The wearing of ash masks is recommended at all times. Everyone is advised to keep listening to Radio Montserrat for information on the activity.

Montserrat Volcano Observatory