Ruapehu - IGNS - Science Alert Bulletin V95/56
Thursday 26 October 1995
1530 hours NZDT (UT +13)
Ruapehu Volcanic Activity
As of 1530 hours, the following information is available.
* At about 2000hr yesterday evening seismic activity at Ruapehu began
to increase from the low levels which had prevailed during the previous
45-50 hours. The level of volcanic tremor increased so that signals were
again being recorded from the Chateau seismogram, and tended to over load
on Dome. This initial activity continued to 2400hr. Seismic activity
again increased at about 0200hr (26 October) and built to a peak between
0500 and 0900hr, declining to a lower level about 1100hr and remaining at
that level till this time.
* Although the seismicity increased overnight there are no reports of
ash emissions, which is slightly anomalous. However conditions for viewing
have been poor as a result ofthe volcanic fog (VOG) and low cloud about
* Vigorous emission of a white-brown gas-rich plume (volcanic fog,
VOG) continues to occur from the summit crater of Ruapehu. This plume has
been reported by various aircraft during the day, many reporting strong
odours. The plume appears as a brown colour (due to the high SO2 levels)
and many observers have mistaken this for ash enrichment. The plume
continues to be ash poor.
Conclusions and Alert Status
The present eruption episode is continuing, with an increase in activity
over the last 24 hours, with significant gas emissions and intermittent
very small ash eruptions. We advise the Alert Level remains at 3.
BJ Scott for
Dr CJN Wilson, Programme Leader, Volcanology