Montserrat Volcano Observatory

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

The cyclical pattern of activity at the volcano continued with explosive eruptions occuring at intervals of 10 to 12 hours. There were two events in the last 24 hours at 09:55 pm on 7th August and 10:32 am 8th August.

The earthquake count for the reporting period is 12 rockfall signals, 5 long period earthquakes and 136 hybrid earthquakes. The hybrids were largely concentrated in a swarm between 03:34 am and 12:35 pm, the explosion at 09:55 pm last night was unique to date in that it was not preceeded by a hybrid swarm.

Violent explosions occured at 09:55 pm and 10:32 am with load rumblings heard at the observatory. At 10:32 am the explosion column rose vertically to 1500 to 20000 feet. Because the wind was in a northerly direction heavy ashfall was experienced throughout the North of the island with pieces of pumice 2-3 cm in diameter falling in St Johns. Intense pyroclastic flows were observed after this explosion. A helicopter flight at 11:55 showed that flows had reached down Mosquito Ghaut to Harris, down Tuitts' to Farms and down White River to two bends below the Great Alp Waterfall. It was also observed from the helicopter that there had been small flows in White Ghaut and Tar River Valley in the East. From the observatory flows were observed down Gages and in the Belham River Valley but ash clouds stopped these being confirmed afterwards from the air. It is likely that pyroclastic flows also resulted from the explosion last night but these were not observed.

All ghauts on the volcano are now filled with hot pyroclastic flow deposits and under no circumstances should people venture into this area. It is expected that as the current elevated level of activity continues further pyroclastic flows will occur on all flanks of the volcano. This makes Plymouth extremely dangerous. The Belham River valley is also very dangerous and should not be entered at all. Access to the exclusion zone is completely restricted, and people should stay away from the flanks of the volcano. The central zone is evacuated overnight and people should not return to there homes until advised to do so. After an explosive event moderate ash fall can be expected throughout the island. When this occurs people in the northern zone should stay indoors until the fall is over. Ash is present in the atmosphere and dust masks should be worn outdoors. Everyone should continue to stay alert and listen to Radio Montserrat for any announcements.

Montserrat Volcano Observatory