Ruapehu's crater lake warms up
Wednesday, 18 March 2020
Ruapehu's Crater Lake is heating up.
The temperature of the lake, Te Wai ā-moe, warmed from 24 degrees Celsius to reach about 40 degrees during February due to hot gases and hydrothermal fluids following volcanic earthquakes beneath Mt Ruapehu, GNS Science said.
Water samples collected by volcanologists from the lake are being analysed to understand the current volcanic activity with results expected by next week, said duty volcanologist Art Jolly. However, such heating cycles were common.
An earlier upwelling of grey sediment and sulphur slicks on the lake surface had now changed to a uniform grey colour.
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'The continued flow of gases and hydrothermal fluids through the lake show that the volcano's vent underlying crater lake is open,' Jolly said.
The lake was overflowing at the outlet channel, with a notable decrease in the flow rate since the last two visits by scientists.
Volcanic tremor had increased in response to the volcanic earthquakes, he said, peaking in early March. This had declined slowly until Wednesday.
Modelling showed that the heat energy input into the lake increased from around 200 MW to around 600 MW. This had now declined as the temperature rise had slowed.
Carbon dioxide and sulphur gases, measured in the atmosphere above the volcano in late February, were greater than when measured on February 7 but the recent values were not unusual and within the ranges measured over the past year.
The Volcanic Alert Level - which reflects the current level of volcanic activity and is not a forecast of future activity - remains at Level 1.
While the changes were within recent parameters, GNS said Mt Ruapehu was an active volcano and had the potential to erupt with little or no warning when in a state of volcanic unrest.