Government Information Service

The Volcanic Explanation
For The 24 Hour Period Ending 6 PM On Tuesday December 31, 1996
A Presentation Of The Government Information Services
In Conjunction With The MVO.

Seismic activity continues with hybrid earthquakes, banded tremor and rockfalls. The size of the banded tremor has decreased slightly and they are approximately 5 hours apart. There were 24 hybrid events, 19 rockfalls, 2 long period and 2 small VT earthquakes. This is a slight reduction since yesterday.

Visibility was good for most of the period, with almost continuous rockfalls occurring from the October 1 dome. The texture of the new material seems to have changed. There were also rockfalls from the northern side of the pre-September dome towards the Farrell's Wall. The ashclouds from these rockfalls were small and the wind blew them towards the west.

It was possible to measure the cracks on Chances Peak and the one nearest the Galways Wall opened up about 2 cm in the last 10 days. The deformation of the crack has slowed and possibly the wall as well.

With the good weather conditions today (Tuesday) many tasks were carried out. Gravity and GPS measurements from Amersham to Chances Peak and Chances Peak steps. EDM measurements to Castle Peak and O'Garras to Chances Peak. Photographs from fixed locations will be used with Theodolite measurements to estimate the growth of the dome. COSPEC measurements were also taken. It was also possible to take samples of rocks from the December 11 dome and material from the top of the October 1 dome.

The sirens will be tested tomorrow (Wednesday) between 3 pm and 6 pm.

Activity could escalate without warning with large pyroclastic flows into the Tar River Valley the main hazard or the sudden collapse of the Galways Wall. Either of which could have serious effects in the evacuated area. The alert level remains at ORANGE and there should be no one in Zones A,B,C, and D on the revised volcanic alert map for December.

THE MVO would like to thank everyone on Montserrat for their support and cooperation during 1996 and look forward to continuing good relations in 1997.

A very Happy New Year from the GIS.

Government Information Service