Ruapehu Crater Lake has begun heating again, although volcanic activity still remains low.
Since mid-July, the temperature of the crater lake has risen from 11C to 26C on Tuesday. While GeoNet said the lake can experience drops in temperature due to some occasional input of snow melt and heavy rainfall into the lake, these short-term variations don't affect the long-term heating or cooling trends.
Water samples were collected from the lake on August 23 and analysis of fluids and gases in these are within the range previously measured at Ruapehu. Additionally, gas isotope data suggested the lake heating episode is being driven by new magma deep in the system, which is expected at the start of heating episodes.
"The level of volcanic tremor recorded by our seismic equipment has remained weak during 2023, while a few earthquakes have been located beneath the volcano," GeoNet said.
"Our new scanDOAS gas scanning equipment continues to measure low-to-moderate levels of SO2 gas output most days during the month, indicating volcanic gases are flowing through the volcano."
The rise of lake temperature is consistent with past heating episodes at Mt Ruapehu and continues to produce a low level of volcanic activity in the lake. This is supported by the current low levels of volcanic tremor, the very small changes in lake chemistry, and low-to-moderate levels of SO2 gas output, GeoNet said.
As a result, the volcanic alert level remains at level 1 and the aviation colour code remains green.
Volcanic alert level 1 means the primary hazards are those expected during volcanic unrest: steam discharge, volcanic gas, earthquakes, landslides, and hydrothermal activity.
While volcanic alert level 1 is mostly associated with environmental hazards, GeoNet warned there is the potential for eruption hazards and eruptions can still occur with little or no warning.
