Possible end of cooling episode at Te Wai ā-moe (Ruapehu Crater Lake). The Volcanic Alert Level remains at 1.
Since last week’s update, Te Wai ā-moe (Ruapehu Crater Lake) seems to have stopped cooling, with daily temperatures remaining at around 11°C. Sulphur dioxide gas emissions rose briefly to 800 tonnes per day (t/day) before declining again to ~200 t/day, and a swarm of very small earthquakes occurred beneath the volcano, although these were too small to be precisely located. Together, these minor changes suggest that a new heating episode could be starting at the crater lake.
No other unusual changes have been observed, and the Volcanic Alert Level remains at 1 and the Aviation Colour Code at Green.
Episodes of renewed heating beneath Ruapehu are typically preceded by local earthquakes and signs of heat and gas flowing upwards into the volcano. Clusters of very small earthquakes were detected by some of the seismometers on Ruapehu, but their exact locations and depth could not be determined. There is no evidence they are directly related to the swarm of earthquakes that occurred two weeks ago 10 km east of Ruapehu. Volcanic tremor, a key indicator of volcanic fluid movement, did not notably change and remains weak. During the past month, the temperature of Ruapehu’s Crater Lake has stopped declining and remained steady around ~10 to 12 ºC which is low but still indicates a continuous low level heat input.
Last week’s pulse of volcanic sulphur gas measured by our continuous gas emission detectors shows that the top of the volcano is not sealed, and a lack of other observed changes at Ruapehu indicates that the volcano continues to exhibit typical low levels of activity.
In summary our recent observations are consistent with minor volcanic unrest, therefore, the Volcanic Alert Level remains at 1 and the Aviation Colour Code remains Green.
More information:
Mt Ruapehu is an active volcano and has the potential to erupt with little or no warning when in a state of minor volcanic unrest.
The Volcanic Alert Level reflects the current level of volcanic unrest. The Volcanic Alert Level should not be used to forecast future activity.
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, potential for eruption hazards also exists and eruptions can still occur with little or no warning. Volcanic Alert Levels 3, 4 and 5 are reserved for eruptions with varying impact distances.
For information on access to the Mt Ruapehu area, please visit the Department of Conservation’s website on volcanic risk in Tongariro National Park and follow the DOC Tongariro Facebook page for further updates.
For information about responding to volcanic activity there are guidelines from the National Emergency Management Agency
Earth Sciences NZ Volcano Monitoring Group and the National Geohazards Monitoring Centre continue to closely monitor Mt Ruapehu for further changes.
Michael Rosenberg
Earth Sciences NZ Duty Volcanologist
Media contact: 021 574 541 or media@gns.cri.nz
