Nov 28 2001, 3:00 pm - Ruapehu Volcano

GNS recorded at moderate-large volcanic earthquake at Ruapehu at 2.18 am on November 21 reported in Alert Bulletin, RUA-01/02. At that time we did not believe there had being an eruption. On Sunday November 25 seismic activity declined to typical background levels and remains low.

A visit was made to the Crater Lake on November 25. The lake has changed to a battleship grey colour from its blue-green colour of recent months. There was upwelling in the lake. This upwelling tends to disturb fine sediments which accumulate on the lake floor (and vent), and suspends them in the water column. There was no evidence of any eruptive activity. The lake temperature was 22°C, compared to 21°C in September.

The relatively low lake temperature is consistent with there not having been any eruptive activity, as steam eruptions through the lake tend to heat the lake water fairly rapidly.

The sequence of events over the last week are typical behaviour for Ruapehu.
GNS volcanologists will continue to closely monitor Ruapehu and further updates will be issued as necessary.

Ruapehu remains at Alert Level 1.

Brad Scott
Duty Volcanologist