Tremors decrease, as experts keep eye on Ruapehu
Activity at Mt Ruapehu is showing signs of decline after more than six-weeks of rising temperatures and unsettled volcanic behaviour.
But experts remain wary and say minor eruptive activity is now likely to occur.
Since March, volcanic tremors had been recorded on Mt Ruapehu and over the past two weeks had reduced, shifting from strong to moderate levels.
The temperature of Te Wai ā -moe (The Crater Lake) had also dropped to 37C from a peak 41C last week.
But gas emission levels remained high along with upwelling in the northern vent areas of the lake which indicated there was still heightened unrest.
‘‘A gas measurement flight on 13 May 2022 confirmed high sulphur dioxide and carbon dioxide gas output, respectively of 179 and 1658 tonnes per day. Both gases are released from relatively shallow magma, and although the gas output values are lower than the values measured two weeks ago, they remain elevated for Mt Ruapehu,’’ duty volcanologist, Agnes Mazot said.
‘‘Overall, even with the lower levels of volcanic tremor and decrease in lake temperature, gas emissions remain elevated, and the period of heightened volcanic unrest continues at Mt Ruapehu.
‘‘Within the next four weeks, the most likely outcome of this unrest episode is minor eruptive activity that is confined to the lake basin, or no eruptions. This level of activity may generate lahars (dangerous volcanic mudflows) in the Whangaehu River.’’
Mazot says the next most likely scenario could be a bigger eruption with volcanic surges and one which generates lahars in multiple catchments where the summit plateau is affected.
An eruption of this size would cause life-threatening hazards on the summit plateau and in valleys impacted by lahars.
But this would most likely only follow a sequence of smaller eruptions.
‘‘The chance of a prolonged eruptive episode or a larger eruption, with wider ashfall impacts, is higher than it was two months ago, but within the next four weeks remains very unlikely.
‘‘GNS Science staff are carrying out more frequent aerial observations and gas measurements when weather conditions are suitable.
‘‘Our interpretation of the observational data and activity is consistent with elevated volcanic unrest at the heightened level and therefore the Volcanic Alert Level remains at Level 2. The Aviation Colour Code remains at Yellow,’’ Mazot said
For information about responding to volcanic activity there are guidelines from the National Emergency