The latest observation of volcanic activity shows New Zealand's largest volcano is experiencing an "uncommon style of earthquake activity" near its summit.
GNS Science found Mt Ruapehu has experienced up to six earthquakes a day over the last month.
Monitoring of the volcano includes seismic, acoustic, GNSS (GPS) sensors around the volcano, gas flights and sampling of the lake.
"In addition to a recent drop in lake temperature, in recent weeks Ruapehu has experienced some minor earthquake activity," GNS Science shared on Tuesday.
GNS Science said re-examination of seismic data has revealed the earthquakes commenced at least as early as mid-February.
"The earthquakes are small and were initially difficult to identify without careful examination of the data as they are uncommon at Ruapehu and only the larger examples are detected by our automatic systems," it said.
"Over the last month, we have seen a maximum of six of these earthquakes a day, and on many days none at all.
"Mt Ruapehu is an active volcano and has the potential to erupt with little or no warning when in a state of minor volcanic unrest."
Observations found the earthquakes consist of 10 minutes of ground shaking.
"While we are able to determine a location for some of the larger examples, the small size and style of the activity means our locations, especially depth, are quite uncertain."
However, it speculated that they originate "near the summit area of the volcano within a few kilometres' depth beneath the surface".
According to GNS Science, the earthquakes are "quite different in appearance" compared to volcanic tremors traditionally seen at Ruapehu.
"While the earthquakes represent something new at Ruapehu, and we are working on understanding the details of the processes driving them, they are not thought to pose any concerns for eruptive activity."
The Volcanic Alert Level remains at 1, and Aviation Colour Code at Green.
Volcanic Alert Level 1 indicates the primary hazards are those expected during volcanic unrest: steam discharge, volcanic gas, earthquakes, landslides, and hydrothermal activity.
"While Volcanic Alert Level 1 is mostly associated with environmental hazards, potential for eruption hazards also exists and eruptions can still occur with little or no warning."
GNS Science and its National Geohazards Monitoring Centre are closely monitoring the volcano for further changes.
