Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 29 August
to 4 pm 30 August 1997

Activity at the volcano has increased today. The main activity has been a series of pyroclastic flows in Mosquito Ghaut and the subsequent development of a respectable sized ash cloud.

Over the last 24 hours 7 hybrid earthquakes, 7 VT earthquakes, 32 long-period earthquakes and 102 rockfalls triggered the broadband seismic network. Of 32 long-period earthquakes, 17 were associated with rockfall signals.

The main phase of activity today involved a series of pyroclastic flows on the northern side of the volcano. These were generated by collapse of material from the lava dome above Mosquito Ghaut. There were some small pyroclastic flows this morning in both Gages Valley and Mosquito Ghaut. The main phase of activity began at 12:57 pm and increased to a peak at around 2 pm. Small pyroclastic flows have continued after this time to and beyond the end of this reporting period. Ash rose up to around 7000-10,000 feet (2100-3000 metres) above sea level and was carried west and north-west by the wind. The pyroclastic flows extended as far as the school at Harris village. The upper part of Mosquito ghaut is now completely full and this afternoon's activity had eroded a new deep gully in the deposits just below the dome. This new gully guided the pyroclastic flows of the late afternoon across the Farrell's plain towards the north-west, confirming that the newly created topography favours future flows moving down the Belham valley. The activity died down by 5 pm to gentle ash emission. A secondary phreatic explosion was observed where the new flows had buried a small pond of water.

Collapse of material from the dome may lead to further explosions and these may be more intense and longer lived than previous explosions. Explosions are also possible without much warning - as happened in early August. If an explosion does occur, small rocks and ash can fall anywhere on the island. The central zone should be evacuated immediately, and people in the northern zone should seek shelter under a strong roof as soon as possible. Helmets or other head protection should be used and dust masks should be worn outdoors. Ash and falling rocks can make driving hazardous.

Further pyroclastic flow activity is anticipated, possibly without any warning. All ghauts on the volcano are now filled with hot pyroclastic flow deposits and this makes all of the exclusion zone extremely dangerous because the flows will not be confined by the ghauts. The changes today in Mosquito Ghaut and material accumulating behind St. George's Hill may now make it increasingly likely that pyroclastic flows will travel into the Belham River valley from the Gages Valley and from the upper part of Mosquito Ghaut. Access to the exclusion zone is completely restricted, and people should stay away from the flanks of the volcano. People should remain vigilant and continue to listen to Radio Montserrat.

Montserrat Volcano Observatory