Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 29 March
to 16:00 30 March 1997
The current alert level is AMBER

Volcanic activity increased significantly today. During a period of about an hour and a half from 1:30 pm to 3:00 pm there was continuous rockfall and pyroclastic flow activity over Galway's Wall, with flows reaching 3.2 km from the Galway's Wall.

A total of 4 volcano-tectonic, 5 hybrid and 12 long-period earthquakes were recorded. This is about the same number of these type of events as yesterday. However the seismic records have been dominated by rockfall and pyroclastic flow signals. There have been 48 rockfall signals, and between 1:30 pm and 3:00 pm there was high amplitude tremor on three of the seismic stations representing continuous rockfalls and pyroclastic flows over Galway's Wall. For a short period the signals exceeded the maximum level of tremor than can be recorded on the seismometers. Large ash clouds to over 10,000 feet were produced by this activity, and these drifted to the west over St. Patrick's and Plymouth. Since this time the level of activity has decreased, but there have still been several small pyroclastic flows over the Galways wall towards the south-west.

Observations were made today from the helicopter throughout the heightened level of activity. The pyroclastic flows were generated in pulses and there was vigorous convection of the mushrooming ash clouds. Many of the flows have now travelled past the road to Galway's Soufriere and the furthest flows travelled to approximately 3.2 km from the Galway's Wall down the White River. The flows have currently been confined to the bottom of the White River Valley with little damage to the sides of the valley. Inspection of the Upper Galway's Wall revealed a 20 m deep chute that has been eroded into the upper part of the wall by numerous pyroclastic flow and rock-fall activity. A substantial amount of rock fall talus has also been built up at the base of the wall and the Galway's Soufriere has been partly buried by flow deposits. Some vegetation was observed to be burning.

A GPS survey on the eastern flanks of the volcano was carried out today. COSPEC results from the runs carried out on Friday show that the current average flux of sulphur dioxide from the volcano was 160 tonnes/day.

Today's heightened activity is a result of dome growth of the southern part of the dome adjacent to the Galway's Wall and shows that pyroclastic flows from the dome can occur at any time. It is dangerous to spend the night in evacuated areas, because the situation could worsen rapidly again over a period of a few hours. People should not enter zone C tonight and should listen for further updates of the situation from the MVO. For the time being people are advised to be vigilant while the new activity is being assessed. The Tar River Valley and White River area all the way to the sea are very dangerous and should not be entered at any time.

Montserrat Volcano Observatory