Ruapehu - IGNS - Science Alert Bulletin V95/41

Saturday 14 October 1995
1600 hours NZDT (UT +13)
Ruapehu Volcanic Activity

Situation Summary

As of 1730 hours the situation is as follows:

*     Volcanic tremor continued at fluctuating but generally low levels
during most of the last 24 hours.  The tremor record from the Dome
(summit) instrument has been strongly banded into intervals of relatively
high and low tremor. Two small (ML 1- 1.5) volcanic earthquakes were
recorded at 0434 and 0634 hours today.  A period of more intense tremor
commenced at 1550 hours today, and had increased to moderate to strong
levels by 1630 hours.  This increased tremor is accompanied by vigorous
ash emission.  This situation is developing at present.

*     Bad weather has prevented ground observations of Ruapehu, and no
field work at the volcano has been carried out by GNS staff.  An aircraft
reported sighting an ash plume  from the volcano at c. 0700 hours today.
CAA has received reports of other aircraft encountering ash at various
locations including near Taupo and Hastings.  We are presently receiving
reports of heavy ash fall at Waiouru, and large plumes seen from
aircraft.

*     Observations of the crater yesterday afternoon showed intermittent
ash eruptions from the deep southern  vent in the now dry crater basin,
with mostly steam and gas emitted from the not clearly observed northern
vent.  This was the reverse of the situation observed during the
overflight yesterday morning, suggesting alternation of the ash emission
vents.

Summary and Alert Status

The present eruption episode is continuing. From 1630 hours today tremor
levels have reached levels last seen during the October 11 - 12 eruption
We advise that the Alert Level presently remains at 3, but is under hourly
review.

Dr IA Nairn for
Dr CJN Wilson, Programme Leader, Volcanology.