The activity at the Ruapehu’s Crater Lake (Te Wai ā-moe) is characterized by roughly regular periods of heating and cooling cycles.
In late December 2020 the lake heated to 43 °C marking the high point of that cycle. Later in April of 2021 a 2nd cycle reached a maximum of 41 °C. The latest cycle is the third this year and the heating phase lasted from early July to early September 2021, during which the temperature rose from 20 °C to 39 °C. During the heating cycle the lake color changed to a darker grey, from a blue-green colour. This is typical as sediments on the lake floor are disturbed during the influx of hot fluids and are suspended in the lake water.
The modeled heat flow into the lake has now dropped from 350-400 MW at the peak of the heating to around 200 MW (megawatt).
The Volcanic Alert Level remains at Level 1 and the Aviation Colour Code remains at Green.
Source: GeoNet New Zealand volcano activity update 27 September 2021
