Since mid-October last year, the Te Wai ā-moe (Crater Lake) temperature has been slowly increasing.
The lake has been slowly reaching 29 ºC, indicating a new heat episode is coming. The temperature lake has been temporarily affected by summer rainfall as the temperature has dropped sharply. The heat flow into the lake is currently around 280 MW, typical of when the lake is heating.
The GNS Science continues: „This new heating episode is accompanied by monitoring trends typically associated with crater lake heating at Mt Ruapehu. Over the last few weeks, the lake colour has changed from a blue-green tinge seen when the lake is cooler to the more common grey colour seen when warm. Minor upwellings are present in the lake, and sulphur slicks are present on the lake surface. The lake is overflowing, which is typical during the summer meltdown. The change in lake colour is consistent with more gas flow disturbing sediment at the base of the lake, which is now suspended in the lake water. This indicates the vents at the bottom of the lake are at least partially open, allowing hot gas and steam to drive the increase in lake temperature. Volcanic tremor, a key indicator of volcanic fluid movement, remains low, and other monitoring indicators are within normal ranges.“
The seismic instrument detected a period of small clustered earthquakes at depths between 3-8 km under the volcano in late November. Quakes ranged between M 0.3 and 2.4. The other monitoring parameters like volcanic tremor, heat flow, gas flow, and lake surface behaviour are all typical of a heating episode in the crater lake, which is being driven by shallower processes. Data observed to date is typical of the past processes seen in the active hydrothermal system associated with the crater lake.
The scanDOAS gas measurements measured moderate levels of SO2 emissions.
Thus, The Volcanic Alert Level remains at 1 and the Aviation Colour Code at Green.
Source: GNS Science volcano activity update 6 February 2024