Sep 25 1995, 9:30 am - Ruapehu Volcano

Situation Summary

As of 09:30 the following information is available:

• About 12 midnight the frequency of volcanic earthquakes increased significantly. Strong tremor was recorded at approximately twice the intensity of activity yesterday until about 9:00 and thereafter declined slightly, and seismic signals reflecting individual explosions merged to form a confused signal.

• There is a substantial eruption column from the volcano, with the products of many moderate-sized individual explosions merging to form a continuous plume.

• An ash plume is drifting to the east for several tens of kilometres, rising to heights of about 10 km. Ash is being deposited over the Desert Road and into the Kaimanawa Mountains.

• A substantial lahar is presently flowing down the Whangaehu valley, and the situation is being monitored by DoC, ECNZ, and NZ Rail. The lahar is up to level 4 on the NZ Rail monitoring system. The lahar has declined in size since 09:00.

Conclusion and Alert Status

A substantial eruption involving new magma is under way at Ruapehu. In the light of our observations and conditions around the mountain, and the marked escalation in seismic activity, we would advise that the Alert Level for Ruapehu be raised to Level 4, effective now.

C.J.N. Wilson
Volcanology Programme Leader