Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 17 March
to 16:00 18 March 1997
The current alert level is AMBER

Activity at the volcano continued at a similar level to yesterday for the first half of the reporting period. There has been a reduction in activity since around 4:00am this morning. Small ash clouds derived from the rockfalls have been intermittently observed as they were carried westward by the prevailing winds. In general it appears that the dome is continuing to grow at a low rate.

The earthquake swarm which began yesterday at 6:44 am continued at a similar level until about 4:00 am this morning when there was a reduction in number and intensity of events. The swarm continued from then until 4:00 pm this afternoon. Since 4:00 pm yesterday 123 hybrid earthquakes and 4 volcano-tectonic earthquakes have been recorded. All of these earthquakes were located at shallow depths beneath the crater. Six rockfalls were recorded by the network today, which is about the same number as yesterday. Low amplitude tremor on the Gages station picked up in intensity from 11:00 am this morning and is continuing at present.

New pyroclastic flow deposits formed overnight were observed in the valley below Galway's Wall. The flows are reaching just over a kilometre from the crater wall. The maximum run-out distance of these flows is gradually increasing. The lack of evidence of burning of the vegetation suggests that the material involved is relatively cool, most likely coming from the pre-Sept 17th, 1996 dome. Small rockfalls into the upper Tar River Valley were observed coming mainly from the south-eastern side of the dome complex

The long occupation GPS survey between Hermitage and Harris was completed today. The results will be released in a future report. A helicopter survey of the talus deposits at the foot of the dome complex in the Tar River Valley was performed this afternoon. The results are currently being processed.

The COSPEC measurements carried out yesterday along the coastal road between O'Garro's and north of Plymouth indicate an average sulphur dioxide flux of 317 tonnes per day. This similar to the amount measured two days ago.

During the last few days the eastern slope of the dome continues to be unstable. Given that the dome is now large and continuing to grow, albeit slowly at the moment, a large collapse and pyroclastic flows could happen with little warning. The increase in activity from the Galway's Wall makes this area particularly hazardous. It is dangerous to spend the night in evacuated areas, because the situation could worsen rapidly over a period of a few hours. People entering Zone C are reminded to remain alert at all times, and spend the minimum possible time in the evacuated zone. The Tar River Valley and the upper Galway's area are very dangerous and should not be entered at any time.

Montserrat Volcano Observatory