Government Information Service

The Volcanic Explanation
For The 24 Hour Period Ending 4 PM On Wednesday July 23, 1997
A Presentation Of The Government Information Services
In Conjunction With The MVO.

The alert level system has been revised by zones.

Today the level of activity at the Soufriere Hills Volcano has been slightly higher than yesterday with rockfalls remaining the main seismic signals recorded. Again very little activity was visible on the dome. No good views of the dome were possible today as the summit was covered in low cloud.

70 rockfalls, 3 long-period earthquakes, one volcano-tectonic earthquake, and one regional even were recorded today. The regional event was located in the region of Barbuda. Also there were several periods of low amplitude broadband tremor again recorded at the St. George's Hill seismic station.

The EDM line between Waterworks and Lees Yard was measured today, but it still does not show any long term 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.

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