Mt Ruapehu status update: Crater Lake (Te Wai ā-moe) is now heating

Published: Tue Dec 14 2021 10:45 AM

Volcanic Activity BulletinRUA – 2021/06
Tue Dec 14 2021 10:30 AM; Ruapehu Volcano
Volcanic Alert Level remains at 1
Aviation Colour Code remains at Green

Another heating phase has started at Mt Ruapehu and Crater Lake temperature has now reached 31 °C. The Volcanic Alert Level at Mt Ruapehu remains at Level 1.

Typically, over periods of months, Ruapehu’s Crater Lake (Te Wai ā-moe) undergoes heating and cooling cycles.

From early July to early September 2021, the lake temperature rose from 20 °C to 39 °C. Through to mid-October the lake temperature declined to around 23-25 °C. Since early December a heating trend has become established, and the lake temperature is now 31 °C. As is common during these heating phases, small volcanic earthquakes have been recorded since the lake temperature started to rise, caused by an increasing influx of hot steam into the lake.

The modelled heat flow into the lake is currently estimated at about 250 MW (megawatt), up from 50 MW in October/November.

Plot of the daily average Crater Lake temperature as measured at the outlet since July 2021. Short duration spikes in the data are not necessarily representative of the whole lake.

Plot of the daily average Crater Lake temperature as measured at the outlet since July 2021. Short duration spikes in the data are not necessarily representative of the whole lake.

The lake colour is a dark grey 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 lake is currently overflowing into the Whangaehu river.

The results from our continuous monitoring of seismic activity, lake temperature and water level indicate that key monitoring parameters remain within normal ranges.

The Volcanic Alert Level stays at Level 1 which reflects the current level of volcanic unrest. The Volcanic Alert Level should not be used to forecast future activity.

The Aviation Colour Code remains at colour Green.

Mt Ruapehu is an active volcano and has the potential to erupt with little or no warning when in a state of volcanic unrest.

Volcanic Alert Level 1 indicates 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, eruptions can still occur with little or no warning.

For information on access to the Mt Ruapehu area, please visit the Department of Conservation’s websites on volcanic risk in Tongariro National Park and follow their Facebook page for further updates.

GNS Science and the National Geohazards Monitoring Centre continue to closely monitor Mt Ruapehu for further changes.

Craig Miller

Duty Volcanologist

Media Contact: 021 574 541 or media@gns.cri.nz