Oct 31 1995, 3:30 pm - Ruapehu Volcano

Situation Summary

As of 15:30, the following information is available:

• During the last 24 hours significant tremor has continued to be recorded by the Dome seismograph at Ruapehu. The activity has typically occurred as numerous tremor bursts of 0.5 - 2 minutes duration. The more intense periods of activity are also recorded in an attenuated form on the instruments at Whakapapa and Ngauruhoe. No observations of Ruapehu summit have been possible today, but the seismic activity is similar to that of yesterday, when near-continuous voluminous gas emission was occurring from the northern vent, accompanied by intermittent small ash eruptions, apparently from the southern vent. The gas plume was being blown down the eastern slopes of the mountain, with light ash fall in the Whangaehu valley.

• Aircraft reported a volcanic plume in the vicinity of Lake Waikaremoana at 16,000 to 30,000 ft at about 08:00 this morning. We have received no reports of ashfall today.

• Department of Conservation Turangi staff (Dr Harry Keys) report that a significant secondary lahar appears to have occurred in the Mangatoetoenui Stream, probably on Saturday 28 October. Deposits from a mudflow up to 1 metre above normal stream flow have been recognised just upstream from the Desert Road bridge. This lahar probably originated from rain on thick ash fall deposits covering steep slopes in the Mangatoetoenui catchment. Further similar lahars can be expected.

Conclusions and Alert Status

The present eruption episode is continuing with significant gas emissions and probable small ash eruptions. We advise the Alert Level remains at 3.

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