Oct 3 1995, 6:30 pm - Ruapehu Volcano

Situation Summary

As of 18:30 the situation is:

• Volcanic seismicity has remained at a low level (at or below pre-eruption levels) since the last Science Alert Bulletin at 20:00 yesterday. Volcanic tremor has been recorded fairly continuously, but has remained at low levels. Discrete volcanic earthquakes have been recorded at about 12:40 and 18:18 today, the latter accompanied by a distinct plume emission event.

• Steam-rich plumes rising to heights of 1 - 6 km have been seen above the volcano for much of today. With one exception at 18:18, the explosions feeding these plumes are so small that they are not recorded as volcanic earthquakes. During the morning, the plumes carried up some ash, which was deposited to the north as a dusting over the Whakapapa area as far as the Top of the Bruce road. Ash was also reported in the form of 'dirty' hail and rain as far as the Chateau. Through the afternoon, the plumes contained little or no ash.

• Taking advantage of good weather, Institute field parties have worked on the eastern, southern and northern flanks of the volcano. On the eastern side, one party studied the way in which ash fall material is being eroded as the snow on which it was deposited melts. On the western side, two parties measured and sampled the September 23 lahar deposits in the Whakapapaiti area. Another party undertook further deformation monitoring in the Whakapapa and Turoa areas, while a COSPEC flight to measure SO₂ levels in the plume was successful. Available results will be issued in tomorrow's Science Alert Bulletin.

Conclusions and Alert Status

Seismic information and eyewitness report indicate the volcano is sustaining a mild level of eruptive activity. We thus advise that the Alert Level for Ruapehu remains Level 3.

C.J.N. Wilson
Volcanology Programme Manager