Two weeks ago, Mt Ruapehu’s Crater Lake (Te Wai ā-moe) entered a new heating cycle, accompanied by strong levels of volcanic tremor (volcanic earthquakes). Over the past week, the lake has heated further to ~32 °C (from 31°C last week). The slow heating has been hindered by heavy rainfall at the volcano and influx of cold water into the lake. The strong tremor reported last week continues.

Sustained elevated tremor, combined with the slow lake heating, continues to indicate that gas is fluxing through the system. However, the slower-than-expected increase in lake temperature suggests a partial blockage may exist in the vent beneath the lake, preventing the hot gas from entering the lake. This could allow pressure to build up within the volcano.

The interpretation of this activity is consistent with elevated volcanic unrest and therefore the Volcanic Alert Level remains at Level 2. The Aviation Colour Code has been raised to Yellow.

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

The Volcanic Alert Level reflects the current level of elevated volcanic unrest. The Volcanic Alert Level should not be used to forecast future activity. However, at Volcanic Alert Level 2, eruptions are usually more likely than at Volcanic Alert Level 1.

Volcanic Alert Level 2 indicates the primary hazards are those expected during volcanic unrest; steam discharge, volcanic gas, earthquakes, landslides and hydrothermal activity. While Volcano Alert Level 2 is mostly associated with volcanic unrest 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.

Geoff Kilgour Duty Volcanologist

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

Footnote: You might notice we've made a tweak to the name of these bulletins - from Volcanic Alert Bulletin to Volcanic Activity Bulletin. We've done this because we think it better reflects the purpose of these Bulletins, which can also include more general updates. Any queries, please let us know at media@gns.cri.nz