Ruapehu - IGNS - Science Alert Bulletin V95/21

29 September 1995
11.30 hours
Ruapehu Crater Lake

Situation Summary

As of 11.30 the following new information is available.

*    Over night the levels of volcanic tremor has varied within parameters
similar to the last six days. Strong low frequency  tremor dominated from
1400h to 2200h on 28 September. From 2200h to this reporting time the
level has been lower, but still remains elevated above pre-eruption
levels.  A large volcanic  earthquake (M3.2) was recorded at 0841h and was
accompanied by an eruption column.

*    The eruption at 0841h  produced an eruption column to about 6000m, a
lahar down the Whangaehu catchment (observed) and ashfall south of the
volcano.

*    Eruptive activity at the volcano was relatively quiet through the
night, but clearly activity is still continuing.

*    Institute staff have been unable to conduct an overflight this
morning, due to weather conditions. Views obtained late yesterday (28
September) confirm crater lake is still present but it is considerably
smaller than it previously was.  Several blocky islets could be observed
through the lake surface indicating much of the lake may be relatively
shallow. There is still sufficient water to produce lahars as was
demonstrated by the 0841h eruption

Conclusion and Alert Status

The eruption involving new magma is continuing at Ruapehu.  In the light
of the activity this morning and the present level of seismic activity, we
advise that the Alert Level for Ruapehu remains at Level 4.

BJ Scott for; 
Dr C J N Wilson, Programme Leader, Volcanology. 
Ph: (07) 374 8211; Fax (07) 374 8199