Montserrat Volcano Observatory

Daily Report
Report for the period 6 pm 17 October
to 6 pm 18 October 1997

There have been three explosions during the last 24 hours bringing the total number of explosions since September 22ndt to 70. These explosions were reasonably powerful producing high ash columns and pyroclastic flows with long runouts. Seismic activity remains low.

Last night an explosion took place at 23:18, loud rumbling was heard and a steam-rich vertical ash column rapidly reached at least 15000ft. The initial explosion appeared to consist of two pulses directed in slightly different directions giving the ash plume a Y-shape. The lower parts of the cloud drifted eastwards, middle levels drifted west and upper levels drifted slowly north but there was no fallout in the inhabited area. Pyroclastic flows travelled down Tuitt's Ghaut, Gages valley and Tyers Ghaut.

The second explosion occurred at 6.48 this morning. The ash column reached at least 17000ft and was again steam-rich. Pyroclastic flows ran down Gages Valley, White River and Tuitt's Ghaut and vigorous ash venting continued for some considerable time after the explosion. An observation flight this morning confirmed that pyroclastic flows generated by these two explosions reached the sea at White River (O'Garro's) and Tar River and almost reached the sea in Plymouth.

The volcano was clear for much of the day and the explosion at 15.17 was seen by several observers. The initial explosion appeared to consist of at least two separate pulses one of which was directed to the north. Pyroclastic flows travelled down Gages Valley as far as Gages village and down Tuitts Ghaut as far as the confluence with Paradise River. A pyroclastic flow in the Tar River Valley reached as far as the sea. The ash cloud was vigorous and rapidly reached 20,000ft. The plume drifted west at lower levels and north west at upper levels although there was no ashfall in the inhabited areas.

The level of seismic activity remains low. During the reporting period 4 volcano-tectonic earthquakes, 7 hybrid earthquakes, three long period earthquakes and 7 rockfall events triggered the seismic system. Two of the long period earthquakes generated rockfalls.

The wind direction has changed and most ash is now falling in the Plymouth area. Air quality readings taken for Central Montserrat in the Olveston area and in Northern Montserrat in the Mongo Hill area show that dust levels in the air are low. Readings are taken as an average over the period of the report. Peaks in ash levels still occur, and ash masks should be worn routinely in ashy environments such as close to roads, especially when it is dry.

There is still a possibility that larger explosions could occur without any changes in the seismicity or other parameters. Therefore all residents of Montserrat are reminded to be vigilant, to avoid entering the evacuated zone and to stay tuned to Radio Montserrat for further information.

Montserrat Volcano Observatory