Montserrat Volcano Observatory

Daily Report
Report for the period 5 p.m. 2 July
to 5 p.m. 3 July 1998

The volcano was extremely active today with a major dome collapse and an extended period of pyroclastic flow activity.

Over the last 24 hours 24 rockfall signals, 2 long period earthquakes and 10 volcano-tectonic earthquakes were recorded by the seismic network.

This morning at just after 3 a.m. there was a sudden onset of activity with a very intense seismic signal for 3 to 4 minutes. This was then followed by over two and a half hours of pyroclastic flow activity. Ash fell over the whole of the island and reports were also received of light ashfall in Nevis and St. Kitts. Analysis of satellite images by NOAA in the USA suggested that the ash cloud reached a height of over 45,000 feet. A morning observation flight revealed that the activity was concentrated in the Tar River area with new deposits across the whole of the Tar River and surge zones reaching up Perches Mountain in the south and towards the southern margin of Long Ground in the north. The Tar River delta had increased in size by small amounts. A later flight in mid afternoon showed that a large scoop of material had been excavated out of the dome in its south-eastern sector. Vigorous steaming could be observed from the base of the scar and low level ash venting was occurring from the summit of the volcano. The back portion of the scar could not be seen. Only minor rockfall deposits could be seen in the other ghauts on the flanks of the volcano.

After the pyroclastic flows had subsided this morning, activity continued at a relatively low level with occasional rockfalls and volcano-tectonic earthquakes. Heavy rain at just before noon resulted in a mudflow signal for around 30 minutes.

Then at about 2 p.m. this afternoon a large seismic signal occurred on all stations and lasted for 3 to 4 minutes and had a very low frequency content. As a result of this signal a large dark ash cloud could be seen to rise from the summit of the volcano, and reached a height of 10,000 to 15,000 feet. The ash then moved slowly over to the west and north west over Salem, Old Towne and Olveston. It is thought that this was a result of a small explosion from the dome.

Since this time the volcano has been relatively quiet again with occasional rockfalls and some small volcano-tectonic earthquakes.

A power cut resulted in no dust measurements today, but visual observations showed that dust levels were very high.

This has been a major increase in activity, and further explosions and pyroclastic flwos are possible down all flanks of the volcano. Residents should continue listening to Radio Montserrat in case there are more sudden developments in the state of the volcano.

Montserrat Volcano Observatory