A visit to the summit crater lake of Ruapehu today has confirmed a small hydrothermal eruption has occurred. As suspected, the volcanic earthquake recorded on Wednesday night which triggered the lahar warning system, did produce a small eruption. The effects of the eruption are minimal and confined to the lake basin.

Today’s visit has shown that the temperature of the crater lake has risen from 15°C to 22.5°C. The lake water level has risen over 1m since the last measurement. There is evidence of wave action up to 4-5m above the lake surface; this was not high enough to flow over the tephra dam and form a lahar.

The temperature and water level change are as expected following this style of eruption.

Seismic activity at Ruapehu remains at typical background levels today. No further volcanic earthquakes or volcanic tremor have been recorded over the last 24 hours. Careful monitoring of the volcano will continue.

Alert Status

The Volcanic Alert Level remains at Level 1, signs of volcano unrest.

Brad Scott
Duty Volcanologist