Increased likelihood of eruption
Mt Ruapehu is heating up and experiencing volcanic tremors, prompting GeoNet to say there is an ‘‘increased likelihood of eruptive activity’’.
Mt Ruapehu and Crater Lake/ Te Wai ā-moe are in a heating phase and temperatures have reached 31 degrees Celsius, a GeoNet alert issued last week said.
This temperature rise has been accompanied by strong levels of volcanic tremor, or volcanic earthquakes, leading Geonet to shift the volcanic alert level up to level 2.
‘‘We consider there is an increased likelihood of eruptive activity as strong tremors are indicating increased gas flux through the system,’’ 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.’’
In January, the lake temperature peaked at 32C and then began to decline in late February to 27C-28C.
Since March 13, a heating trend has started and the lake temperature is now at 31C. Volcanic tremors have been recorded often during this time.
The modelled heat flow into the lake is reaching about 330 megawatts, up from 100 megawatts in February.
The lake is now overflowing into the Whangaehu River but the flow level is believed to be minor. 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.
The area within 2km from the centre of Te Wai ā-moe/Crater Lake is now closed to the public and concessionaires due to the increased risk of eruption, the Department of Conservation (DOC) said.
Mt Tongariro and the Tongariro Alpine Crossing and Tongariro Northern Circuit are not affected. All DOC tracks and huts in Tongariro National Park remain open.