Mount Ruapehu has stabilised after a short period of increased volcanic tremor over the weekend.
Photo: Unsplash / Stas Kulesh
It remained at alert level 2, which signalled moderate-to-heightened volcanic unrest with the potential for eruption.
GNS Science said the tremor levels had been weak-to-moderate for the past three weeks.
Volcanic activity increased sharply on Friday and fluctuated between moderate and strong levels of tremor over the weekend.
But a spokesperson said the temperature at Crater Lake had since stabilised and the volcanic tremor had returned to weak levels.
"The return of moderate-to-strong volcanic tremor and stabilisation of Crater Lake temperature are consistent with a continued period of moderate volcanic unrest at Mt Ruapehu.
"We will carry out a gas measurement flight and Crater Lake sampling when the weather allows."
The most likely outcome was no eruption within the next three weeks, but minor activity confined to the lake basin was also possible which could generate volcanic mudflows - lahars - in the Whangaehu River, GNS Science said.
The next likely scenario, but considered very unlikely, was an eruption that impacted the summit plateau and could generate life-threatening volcanic mudflows.
"The chance of a prolonged eruptive episode or a larger eruption, with wider ashfall impacts such as occurred in 1995-96, is higher than it was before the start of elevated unrest in March 2022, but within the next three weeks, this scenario remains very unlikely.
"Such an eruption would most likely only follow a sequence of smaller eruptions."
GNS Science said Mt Ruapehu was an active volcano and had the potential to erupt with little to no warning when in a state of moderate volcanic unrest.
"The increased tremor over the weekend highlights the variability and significant uncertainty about the state of the volcanic process that has been driving the current unrest period.
"Our interpretation of the observational data and activity is, therefore, still consistent with moderate volcanic unrest and therefore the Volcanic Alert Level remains at Level 2. The Aviation Colour Code remains at Yellow."
The National Emergency Management Agency has guidelines about. responding to volcanic activity.