The North Island's largest mountain Mt Ruapehu is currently experiencing a "minor volcanic unrest", with an increasing temperature on its Crater Lake over the past week.
GNS Science who produced the assessment of Mt Ruapehu said a Volcanic Alert Level 1 is in place - which is the lowest alert level for volcanoes.
GNS says over the past two months the lake has cooled to 20 degrees, but since Tuesday last week it has started heating again at a rate of 1 degree per day.
Mt Ruapehu is also experiencing an increase in volcanic tremor, and while GNS says the mountain doesn't show any "unusual signs" of unrest they say it is a useful reminder that eruptions can occur with little or no warning.
Volcanic unrest hazards, which are possible from a Volcanic Alert Level 1, occur on and near the volcano.
They may include: steam eruptions, volcanic gases, earthquakes, landslides, uplift, subsidence, changes to hot springs, and/or mudflows.
GNS hopes to collect water and gas samples from Mt Ruapehu's Crater Lake this week.
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