Ruapehu - IGNS - Science Alert Bulletin V95/54

Tuesday 24 October 1995
1630 hours NZDT (UT +13)
Ruapehu Volcanic Activity

Situation Summary

As of 1630 hours, the following information is available.

*     During the last 24 hours, seismic activity at Ruapehu has further
declined, with volcanic tremor largely absent from the Chateau
seismogram.   The last significant  degassing eruption type event was
recorded at Dome (summit) about 1800 h yesterday. and was followed by
about 5 hours of relative seismic quiet to about 2300 h.  Since then the
Dome record has been characterised by numerous brief (usually <1 minute)
bursts of tremor -probably symptomatic of the crater activity observed
during an overflight at 1005-1024 h today (see below).

*     Vigorous emission of a white gas plume was occurring from both vents
in Ruapehu crater during the overflight today, somewhat obscuring
visibility within the crater.  Very occasional  small bursts of dark ash
rose 50 to 100 m from the central (southern) vent.  Stereoscopic
interpretation of oblique aerial photos taken on October 18, 20 and 24 has
shown that the central vent has deepened during the last week, throwing
into prominence a dark dividing ridge between the central and northern
vents.  We have not identified a dome within either vent.

Conclusions and Alert Status

The present eruption episode is continuing at a reduced level, with
significant gas emission and intermittent very small ash eruptions.  The
Alert Level remains at 3.

IA Nairn for
Dr CJN Wilson, Programme Leader, Volcanology