Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 16 September
to 4 pm 17 September 1997

The level of activity at the volcano has been moderate to high during the last 24 hours. There have been two peaks in pyroclastic flow activity about 12 hours apart. Pyroclastic flows travelled down Tuitt's ghaut during the afternoon and reached beyond the junction of Tuitt's bottom ghaut and Paradise River.

Rockfall activity began to increase last night at about 8pm and developed into a period of sustained pyroclastic flow activity which ended soon after midnight. Activity was low in the early hours of the morning then at about 8am the level of rockfall activity again began to increase until it was almost continuous. For 15 minutes starting at 9.54am there was a succession of 5 moderate-sized pyroclastic flows which travelled down Tuitt's Ghaut; the largest flow reached several hundred metres beyond the junction of Tuitt's bottom ghaut and Paradise River. There were several more isolated pyroclastic flows up until 11.30 am when the level of rockfall activity began to tail off. Activity has been low all afternoon.

The seismicity has been moderate during the reporting period with 56 rockfall events, 9 long period earthquakes and 12 volcano-tectonic events. The volcano-tectonic earthquakes were mostly small but a source for the larger ones has been located at 3 to 3.5km below the top of the dome. Both periods of enhanced flow generation were again characterised by an increase in tremor accompanied by ash and steam venting.

Visibility has been poor again today and the dome remained covered by cloud. Nevertheless, there is no doubt that the dome is still growing rapidly and there is still potential for large pyroclastic flows. Large pyroclastic flows generated on the northern and western sides of the dome are likely to reach the Belham valley. Rapidly moving surges of hot ash associated with such flows could reach areas such as Friths, Old Towne, Salem and Olveston. Such flows and surges could occur with no warning and so people still living in these areas are urged to move north as soon as possible.

In addition to generation of large pyroclastic flows, explosions could also occur. If an explosion occurs, 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.

Montserrat Volcano Observatory