Oct 19 1995, 5:00 pm - Ruapehu Volcano

Situation Summary

As of 17:00, the following information is available:

• Tremor levels have remained low at Ruapehu during the last 24 hours, although numerous degassing eruption type events (without sudden onsets) have been recorded by the Dome (summit) seismograph, along with a few long period earthquakes (as described in RUA-95/48) best recorded on the Chateau instrument. Field parties have observed moderate ash eruptions from the southern vent in Ruapehu crater, at times which correlate with Dome seismic events. At other times, a voluminous gas plume was emitted from the northern vent.

• GNS parties have gone into the field to carry out tilt level surveys at Whakapapa, and examine ash and lahar deposits in the Whangaehu River at Tukino. Results of these investigations are not available at time of this report. A helicopter-lifted party sampled recent ash deposits on the upper slopes of Ruapehu. They encountered a ground-hugging plume of SO₂ gas being blown down the upper slopes at Whakapapa. This experience demonstrated the possible existence of a gas hazard at Ruapehu during suitable wind conditions.

Conclusions and Alert Status

The present eruption episode is continuing at a reduced level, with weak ash but strong gas emissions. We advise that the Alert Level remains at 3 for Ruapehu volcano.

I.A. Nairn (for C.J.N. Wilson)
Volcanology Programme Manager