Nov 17 1995, 5:00 pm - Ruapehu Volcano

Situation Summary

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

• Volcanic tremor is continuing at similar levels to those for the previous 24 hours, i.e. low, but still higher than for last week. A few high frequency volcano-tectonic earthquakes have been recorded today.

• We have not observed or received reports of any ash emissions today. A plume to 12,000 feet was reported (via Met Office) at 09:00 today. A gas plume at 10,000 feet was reported by an aircraft 20 miles west of Napier at 12:15 today. Emission of the normal gas plume from the crater was observed by a GNS party at Tukino.

• A COSPEC (SO₂) flight yesterday was not able to obtain measurements of the diffuse gas plume.

• A GNS party has carried out a deformation survey at Tukino today, completing the EDM surveys around the volcano. Tilt-levelling surveys carried out at Knoll Ridge and the Dome yesterday found slight but statistically insignificant (within the survey error) inflation occurring over the last 10 days. A repeat of the Dome tilt-levelling in 7 to 10 days is required to establish the present trend for this site, which has only been reoccupied since the eruption episode commenced.

  Days since last major ash fall* on 14 October 1995	34
  SGV** at Dome: mean for 24 hours to 4:00 pm on 17 November 1995	<2 μm/s
  Days since SGV** last ≥10 μm/s on 27 October 1995	21
  SO2 flux: last measured on 7 November 1995	~2,100 t/day
  Deformation as of 16 November 1995***	steady state
  * 1 mm thickness at 5 km radius ** Seismic ground velocity *** Tilt observed at Dome

Conclusion and Alert Status

At present the level of volcanic activity is low, however we advise the Alert Level remains at 3.

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