Mt Ruapehu is heating up.

Following a temperature increase and volcanic tremors, GeoNet says there’s an “increased likelihood of eruptive activity”. While the Aviation Colour Code remains at Green, Ruapehu’s Volcanic Alert Level has been raised to Level 2.

Mt Ruapehu and it’s Crater Lake (Te Wai ā-moe) has reached a temperature of 31 °C. This is not uncommon. Over a period of months, Ruapehu’s crater lake undergoes heating and cooling cycles. A new heating cycle has started and has been accompanied by strong levels of volcanic tremor.

GNS Science, Duty Volcanologist Craig Miller said, “Despite an increase in gas flow, the lake temperature is only responding slowly, suggesting a partial blockage may exist in the vent beneath the lake. This could allow pressure to build up within the volcano”

GNS Science volcanologist Craig Miller / Supplied

In January 2022 the lake temperature peaked at 32°C. Following this peak, through to late February, the lake temperature declined to around 27-28 °C. The modelled heat flow into the lake is currently estimated at about 330 MW (megawatt), up from 100 MW in February 2022.

The crater lake is currently overflowing into the Whangaehu River, however, the flow level is believed to be minor.

Miller said that the lake colour is expected to change to a darker grey colour as sediments on the lake floor are disturbed during the influx of hot fluids heating the lake.

Primary hazards of Volcanic Alert Level 2 that are expected during volcanic unrest include; steam discharge, volcanic gas, earthquakes, landslides and hydrothermal activity.

The GeoNet Volcanic Alert Level System

Miller noted that the current Volcanic Alert Level should not be used to forecast future activity. Department of Conservation has closed an area 2km around the crater lake as precaution.

Photo: Department of Conservation (Tongariro)

Mt Tongariro, the Tongariro Alpine Crossing, and Tongariro Northern Circuit are not affected. All DOC tracks and huts in Tongariro National Park remain open.

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