Slight changes in water and gas composition of the Crater Lake (Te Wai Ā-Moe) at Mt Ruapehu

Published: Tue Nov 28 2017 5:16 PM
Updated: Tue Nov 28 2017 12:00 AM

Volcanic Alert BulletinRUA – 2017/02
2017-11-28 16:30:00 +1300 +1300; Ruapehu Volcano
Volcanic Alert Level remains at 1
Aviation Colour Code remains at Green

Measured changes in Crater Lake water and gas composition confirm the slightly elevated level of activity at Mt Ruapehu. The lake temperature (37ºC) and the level of seismic tremor remain unchanged. The Volcanic Alert Level remains at 1.

The Crater Lake (Te Wai Ā-Moe) was visited to sample water and gas on 10 and 17 November 2017. The results from the analyses show a slight increase in Chloride, Sulphate and Magnesium concentrations, and CO-CO2 gas ratio. These changes are consistent with the increase in CO2, SO2 and H2S emission rates measured on 23 November and the sustained high lake temperature (~37ºC) reported in our latest bulletin on Saturday 25 November.

The increase in concentration of these chemical elements, higher gas output and a sustained high lake temperature all suggest a more open pathway for the volcanic gases from depth to the surface. These increases are common in periods of higher lake temperature and have been observed in the past outside eruptive periods. Volcanic seismic tremor is currently at moderate to low levels. Further sampling of the Crater Lake and a gas measurement flight are planned as weather allows.

As weather cleared out overnight, a small steam plume was visible this morning above the crater lake at Ruapehu. Such steam plumes are to be expected due to the current combination of higher lake temperature, gas emissions and atmospheric humidity.

GNS Science continues to closely monitor Mt Ruapehu and our other active volcanoes through the GeoNet project. The Volcanic Alert Level of Ruapehu remains at 1 and the Aviation Colour Code at Green.

Agnes Mazot Duty Volcanologist

Media Contact: Brad Scott
(07 3748211)