Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 6 November
to 6 pm 7 November 1997

Today seismicity has been at an elevated level but, apart from ash venting, the volcano has been outwardly quiet.

The hybrid swarm which started at about 7:30 yesterday evening continued until 2 o'clock this morning. Since that time the seismicity has been dominated by high amplitude tremor - which continues at the moment. As has been the case recently, this tremor has similar frequency content to hybrid earthquakes and so can be assumed to also be related to gas escape from the magma. In the 24 hours before 4 o'clock this afternoon 96 hybrid earthquakes, 1 long period earthquake, 1 volcano-tectonic earthquake and 1 rockfall triggered the seismic network.

Excellent observations of the scar formed by collapse of the lava dome yesterday afternoon were made today. In addition a significant fan of deposits, extending 300m into the sea, at O'Garras has now been formed by the extensive pyroclastic flows which travelled down the White River. The collapse has formed a large scar on the south side of the volcano above Galways. A significant amount of re-growth of dome material has already occurred. Although activity is currently centred on the southern side of the volcano a switch to dome growth on the northern side could occur over a matter of only a few hours.

Throughout the day the volcano has been venting ash. Because of an unfavourable wind direction fine ash has been blown as far north as St Johns. Despite this the 24 hour average level of ash in the atmosphere in central and northern Montserrat was low today with values of 18 micrograms per cubic meter at the MVO and 28 micrograms per cubic meter in Woodlands.

With the tremor continuing as it is another pyroclastic flow can be expected soon. There is no guarantee that such a flow would go down the White River again, it could easily come down Farrells plain instead, in which case there is a danger of pyroclastic flows moving down the Belham valley. There is also a chance that the volcano will start exploding again. Stay tuned to Radio Montserrat for further information.

Montserrat Volcano Observatory