The current level of activity is consistent with minor volcanic unrest behaviour that has characterised Ruapehu throughout the past 16 years. The Volcanic Alert Level remains at 1.

Since the current crater lake was established in 2003, typical heating and cooling cycles have been observed. During these cycles, the temperature ranges between approximately 12 to 40°C over a period of around 12 months. In mid-July we observed the start of a typical heating cycle of the lake from a low temperature of around 14°C, and it is now at about 27°C.

Other monitored parameters like seismicity and chemistry can sometimes change as a response to a heating cycle. We have not observed any changes in the level of volcanic tremor or the lake chemistry to date. As part of our normal routine monitoring, we visited Te Wai ā-moe on the 15 August to collect water and gas samples from the lake. Results from the analysis of the samples showed no changes in the water and gas composition. The crater lake has undergone many heating and cooling cycles in the past and we don’t see this cycle as any different. Therefore, current observations are still consistent with minor unrest behaviour and because of this, we remain at Volcanic Alert Level 1 and the Aviation Colour Code stays at Green.

Volcano Alert Level 1 corresponds to minor unrest. While this is the case, it is a useful reminder that eruptions can occur with little or no warning. GNS Science continues to closely monitor Mt Ruapehu and our other active volcanoes and will provide further information when conditions change.

Agnes Mazot

Duty Volcanologist

Media Contact: Brad Scott (Volcanologist - 07 374 8211)