Montserrat Volcano Observatory

Daily Report
Report for the period 4 pm 13 September
to 4 pm 14 September 1997

Volcanic activity has continued at an increased level today, with especially vigorous pyroclastic flow activity throughout the day. Some of the pyroclastic flows were isolated events demonstrating that high level activity, including pyroclastic flows in the Belham Valley and even explosive events, can occur at anytime.

Seismic activity was dominated by signals from the rockfall and pyroclastic flow activity; 65 rockfall signals were recorded on the short period network, with 2 hybrid events, 4 VT earthquakes and 5 long-period earthquakes. The largest VT earthquake recorded today was located at approximately 4 kilometres below the top of the dome. Due to continued maintenance work connected with the move of MVO, these statistics are a minimum. Again, many of the pyroclastic flows during the reporting period were preceded by long-period earthquakes.

Enhanced rockfall and pyroclastic flow activity has occurred throughout the day. Overnight there was a concentrated period of activity between 11 pm last night and 2 am this morning. Numerous large pyroclastic flow signals were recorded during this period. A second period of elevated activity began at around 9 am this morning and continued until about 1:30 pm this afternoon. During this period there was almost continuous ash generation resulting from large rockfalls and pyroclastic flows. Observation teams reported significant pyroclastic flows travelling down the Farrell's Plain. Pathways have now developed which permit these flow to enter both Tuitts and Tyers ghauts (formerly the 'unnamed ghaut') from the remnant valley of Mosquito Ghaut. Strong winds today generally kept the ash plumes below 5000 feet (1500 metres) above sea level. Staff at Gerald's Bottom Heliport reported that at one point the ash did reach approximately 8000 feet (approximately 2400 metres) above sea level. Ash was blown toward the north-west resulting in ash deposition in Salem, Woodlands and St Peters. Ash-laden steam venting from the summit region of the dome was at a high level throughout most of the day. The majority of activity is still concentrated on the northern flank of the volcano and it is thought that the northern parts of the dome are still the most active.

Activity from around 2 pm onward has been at a relatively low level but there continues to be isolated rockfalls and small pyroclastic flows.

The large size of the dome, its rapid growth rate and the filling of ghauts on the northern flank of the volcano all make it more likely that large pyroclastic flows will reach far down the Belham Valley. This makes areas south of the Nantes River very dangerous and anyone still living in this area is 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.

Rod Stewart left island yesterday afternoon after spending 3 weeks working with the MVO. Rod is gratefully thanked for his valued contribution to the monitoring work and the MVO hopes he can return for further tours of duty.

Montserrat Volcano Observatory