Volcanologists are closely monitoring Mt Ruapehu after recording a volcanic earthquake swarm beneath the Crater Lake.

They have also noticed an increase in the lake temperature.

"We are uncertain of the implications of the recent observations," GNS duty volcanologist Agnes Mazot said.

"However, at this time these changes at Ruapehu are not considered sufficient to change the volcanic alert level.


"Swarms of volcanic earthquakes like these are uncommon on Ruapehu - seismic activity is usually dominated by volcanic tremor," Ms Mazot said.

The temperature of the Crater Lake has been rising since late 2015, and since mid-April this year the temperature has risen from 25C to 40C.

Similar temperatures and rates of temperature increase were observed in March 2011, April 2014 and February 2015.

"We have not noted any changes in other monitored parameters like volcanic gas, lake chemistry or lake overflow."

GNS Science volcanologists continue to closely monitor Ruapehu through the GeoNet project.

Ms Mazot added the changes at Mt Ruapehu were not related to White Island's volcanic eruption on Wednesday.