Minor volcanic unrest at Mt Ruapehu

Mt Ruapehu at 5.50am today. Photo: GeoNet.

Minor volcanic unrest is continuing to be monitored by GNS scientists.

Over the last 5-6 months, measurements of Mt Ruapehu’s Crater Lake (Te Wai ā-moe) temperature, earthquake activity and chemistry have remained consistent with minor volcanic unrest.

"GeoNet continuously monitors for earthquakes, the level of volcanic tremor and acoustic signals around Mt Ruapehu," says duty volcanologist Brad Scott.

These are complemented by a data logger measuring the water level and temperature at the outlet of the Crater Lake (Te Wai ā-moe).

Regular gas flights and lake sampling are also undertaken as weather permits.

Brad says volcanic tremor levels have been low.

He says gas flux and chemical concentrations of the crater lake water remain unchanged or within normal variation.

The lake temperature has hovered around 22-28°C, which is broadly the median lake temperature over the past 10 years (25°C).

"Using numerical modelling, we estimate that 100–200MW of energy input is required to keep the lake temperature at 25°C.

"This equates to 10–20 per cent of New Zealand’s geothermal electrical energy production and shows that despite the apparent quiescence, Mt Ruapehu is still a very active volcano. Like most volcanoes it has the potential to erupt with little or no warning when in a state of volcanic unrest.

"Statistically, over the past 40 years most eruptions at Mt Ruapehu have occurred at temperatures that are very rarely observed (above 39°C and below 16°C)."

The Volcanic Alert Level, therefore, remains at Level 1. The Volcanic Alert Level reflects the current level of volcanic activity and is not a forecast of future activity. There is no change in the Aviation Colour Code from Green.

GNS Science and the National Geohazards Monitoring Centre continues to closely monitor Mt Ruapehu for further signs of activity.

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