Taupō's volcano alert level has been raised for the first time to level one following minor volcanic arrest.
GeoNet said the unrest was causing ongoing earthquakes and ground deformation.
Although this is the first time GeoNet has raised the alert to level 1, it's not the first volcanic unrest at Taupō. There have been 17 previous episodes of unrest over the past 150 years.
"Several of these were more severe than what we are currently observing at Taupō," GeoNet said.
The volcano has not erupted over the past 1800 years before written records were kept and the last eruption at Taupō volcano was in 232 AD ± 10 years.
GeoNet said the earthquakes and deformation could continue for the coming weeks or months, and while some earthquakes may be felt in areas around Lake Taupō, the deformation is currently only detectable by sensitive monitoring instruments.
Whakaari/White Island is currently at alert level 2 and Mount Ruapehu is at level 1.
Volcanic unrest at Lake Taupō continues
Volcanic unrest has continued at the lake for months, which is when magma or magma-heated hot water and steam force its way through the ground under a volcano, producing earthquakes and ground movement.
GeoNet has located a swarm of almost 700 small earthquakes beneath the lake since the start of May, including a 4.2 magnitude shake on September 10.
The movement under the active volcano has also caused the land around the lake to uplift.
"We interpret the ground uplift and earthquake activity to be caused by the movement of magma and the hydrothermal fluids inside the volcano. We have also sampled springs and gas vents around the lake for changes in chemistry that may be related to the earthquake and ground uplift," GeoNet said.
If there was increased unrest there would be more substantial impacts on the local area, including ground shaking, landslides, liquefaction and higher levels of ground deformation, GeoNet said.
While Volcano Alert Level 1 is mostly associated with environmental hazards, the potential for eruption hazards also exists.
