- White Island volcanic alert level had been raised from one to three, with "eruption hazards" near the vent.
- Mt Ruapehu had seen an increase in volcanic tremors.
- Its lake reached 46degC, the highest observed since it reformed in 1999.
- Earlier this month the east coast was hit by a powerful 7.1 earthquake with hundreds of aftershocks
- 7.1 magnitude earthquake earlier this month generated a small tsunami
Volcanic and aviation alert levels have been raised for White Island after a minor eruption.
The aviation colour code has been raised from green to orange, with GeoNet reporting the "volcano is exhibiting heightened unrest with increased likelihood of eruption".
The volcanic alert level had been raised from one to three, with "eruption hazards" near the vent.
On GeoNet's webcam on the island ash can be seen coming from the crater.
"The level of volcanic activity at White Island has increased late this morning with minor volcanic ash been passively emitted from a vent on the 2012 lava dome," GeoNet said.
Last week Mt Ruapehu had seen an increase in volcanic tremors.
GeoNet has also recorded rises in temperature in the mountain's crater lake after extremely low temperatures.
It is now up to 17.6degC, up from a low of 12degC on August 15.
For much of August the temperature ranged between 13degC and 14degC.
"Recently the lake has been cooling and we even discussed the possibility of new record low temperatures," GeoNet said on its website.
"The crater lake displays temperatures that typically range between about 15 and 40degC.
The lake ... has now started to heat rapidly.
"The temperature was starting to rise, very slowly, in late-August, but with quite a bit a lot of variability.
However by 2 September a rising trend was clearly established."
About two days after the lake temperature stared to rise, the level of volcanic tremor also started to rise and has remained.
On May 11, the
This high temperature was also accompanied by volcanic tremor and an increase in the output of volcanic gas.
The Volcanic Alert Level was raised to level 2, lowering to level 1 in early July as output and volcanic tremor levels declined. Volcanic alerts range from 1 to 5, with 1 being "minor volcanic unrest" and 5 being a "major volcanic eruption".
The record temperature for the lake was 60degC in 1968.
Further sampling and visits to the crater lake were planned if weather allowed, Geonet said, which was part of its standard monitoring programme for Mt Ruapehu.
GeoNet obtains temperatures from the lake using a data logger with a temperature sensor in the lake and communications via satellite link.
The east coast of New Zealand was hit by a powerful 7.1 magnitude earthquake earlier this month generating a small tsunami, but officials said there was no significant damage or injuries.
A swarm of aftershocks, several of nearly 6.0 magnitude, rocked the region for many hours after the initial jolt as coastal residents made their way to high ground by torchlight.
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