Montserrat Volcano Observatory

Daily Report
Report for the period 16.00 22 May
to 16:00 23 May 1997
The current alert level is ORANGE

The overall activity at the Soufriere Hill volcano was a slightly higher level during the current reporting period, than it has been in the past few days. The recently established pattern of activity was again repeated, with a period of relatively low level seismicity, followed by a swarm of hybrid earthquakes and ending with an episode of pyroclastic flow generation. Activity appeared to have remained focused along the north to north-western sector of the dome

The period of sustained, elevated activity which started around 2:30 pm yesterday continued through to around 6:00 pm. Volcanic activity then declined and remained at an extremely low level, with the occasional small rockfall events throughout most of the night. A swarm of hybrid earthquake occurred between the period 3:45 am to 10 am this morning. By the time the swarm ended, near continuous rockfalls and small pyroclastic flow activity were already in progress. This generated a highly convective plume of ash which was propelled high over the north-west of the island by the prevailing winds. By 11:00 am most area within the footprint of this plume experienced slight ashfall. The Activity declined after 12:00 noon and remained at a low level for the rest of the reporting period

The upper slopes of the volcano was hidden in the clouds for most of the day, so no observations were made. The wind direction, recent cyclic style of activity (hence more predictable) and the current location of activity on the dome, again provided the opportunity for the scientists to visit Chances Peak. Today,. an extensometer was installed to measure crack width and automatically transmit the information to the MVO. A GPS occupation of the station on site was also done. While at Chances Peak numerous rock fracturing and rockfalls could be heard.

A total of 92 hybrid earthquakes were recorded during the last 24 hours, significantly more than yesterday. There were also 8 long-period earthquakes, and 2 volcano-tectonic earthquakes. The VTs were located at 1.8 and 2.7 kilometres below the dome. Rockfalls occurred occasionally throughout the last 24 hours but most were produced after the hybrid swarm. A total of 83 rockfall signals were recorded.

The volcano remains in a potentially dangerous phase, with the possibility of pyroclastic flows breaking into the northern ghauts. Dome growth continues and an escalation in the level of activity remains possible. The Tar River valley, Long Ground, White's and Tuitt's areas are very dangerous, and should not be entered because of the dangers of pyroclastic flows. Nobody should enter zones A and B, and only essential visits should be made to the evacuated zone. Ash masks should be worn when in the ashy areas.

Montserrat Volcano Observatory