Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 7 September
to 4 pm 8 September 1997

Activity at the Soufriere Hills volcano has been at an elevated level over the past 24 hours and indications are that activity may escalate further over the next few days. Escalations could be rapid and involve pyroclastic flows in the Belham Valley or even explosive activity. All people on Montserrat are thus asked to remain particularly vigilant at this time.

Two episodes of intense pyroclastic flow activity due to collapse of hot lava from the dome have occurred during the reporting period. Both of these periods lasted about an hour and a half, the first late yesterday afternoon and the second just after dawn this morning. A reconnaissance flight this afternoon confirmed that flows have been concentrated in Tuitt's Ghaut and on the Farrell's plain, with maximum runout to the east as far as below Harris Lookout and to the west into the upper parts of the Belham Valley as far as Dyer's Bridge. The Farrell's plain is now covered with big boulders from these flows, and the nature of the topography and deposits means that future flows over this area will be channelled into the Belham Valley, and larger flows could easily reach the Belham Bridge or even the sea.

Ash has been blown today by the strange winds in a north-eastward direction, and heavy ashing has been reported from Antigua, where the VC Bird International Airport has been affected.

Seismic activity has been dominated by the signals from pyroclastic flows during the collapses described above, but in addition to this there have been a number of hybrid earthquakes which have occurred in two swarms prior to this mornings collapse (between 1:00 and 3:00 am) and during this afternoon (between 2:15 pm and the end of the reporting period). The total of hybrid earthquakes for the day is 94, with 76 rockfall signals, 14 long-period earthquakes and 2 vts.

With the re-appearance of hybrid earthquake swarms prior to periods of pyroclastic flow generation and the large size of the dome and its rapid growth rate, it is possible that activity could escalate very rapidly into large pyroclastic flow generation or explosive activity. The southern part of Montserrat is thus extremely dangerous and all areas south of the Nantes River should be evacuated.

If an explosion does occur, small rocks and ash can fall anywhere on the island. People should seek shelter under a strong roof as soon as possible. Helmets or other head protection should be used and it should be remembered that ash and falling rocks make driving hazardous. After ash has fallen it will remain present in the atmosphere for some time and dust masks should be worn outdoors. People should remain vigilant and to listen to Radio Montserrat.

Montserrat Volcano Observatory