Government Information Service

The Volcanic Explanation
For The 24 Hour Period Ending 4 PM On Monday July 14, 1997
A Presentation Of The Government Information Services
In Conjunction With The MVO.

The alert level system has been revised by zones.

The Volcanic Explanation will now cover the 24 hour period from 4 pm to 4 pm. It will be posted as soon as possible after I receive it either via MNI or the volcano page.

The level of activity during the past 24 hours has decreased.

The volcano was overcast for most of today (Monday), but some viewing of the flanks was possible. Measurements made from the MVO and Garibaldi Hill indicate that the north-west part of the dome above Gages valley is at least 950 metres. When the photographs taken yesterday (Sunday) are processed volume estimates will be posted.

Rockfall signals dominated the seismicity today. There were 53 rockfall signals, 4 long period earthquakes and 2 hybrid earthquakes. No volcano-tectonic earthquakes were recorded.

The EDM line between Waterworks and Lees Yard does not show a consistent trend. The new observation sight at Jack Boy Hill, which was set by GPS equipment will be used for future measurements and photographs. The Chances Peak tiltmeter shows no changes since yesterday except to continue to show a deflationary trend.

The recent pyroclastic flows and ash eruptions have not been associated with an increase in seismicity or tiltmeter readings. Anyone entering the exclusion zone is at great risk. Further pyroclastic flows are most likely to occur in Mosquito Ghaut and Gages Valley but pyroclastic flows could also occur in Tuitts, Tar River Valley and White River. There has been no warning of the pyroclastic flows in Gages Valley and this makes Plymouth very dangerous. Belham River Valley could be the sight of pyroclastic surges or hot mudflows. These mudflows are at or near boiling point and travel very fast and may go further than pyroclastic surges.

The pyroclastic flow and surge deposits will remain very hot for several days and should not be approached or walked on to avoid severe burning. Dust masks should be worn when ash is in the air.

Ms. Joan Latchman of the SRU in Trinidad left today after another tour at the MVO

Government Information Service