The North Island's most restless volcano is shuddering, releasing high levels of gas and worrying scientists volcanic activity could be coming this year.
Scientists monitoring Mt Ruapehu reported the increased gas, which was keeping Crater Lake hot, over the last week.
GNS Science duty volcanologist Dr Tony Hursttold the Herald yesterday the mountain was not likely to erupt this year, but the signs did point to an increased risk of volcanic activity.
That could mean steam plumes, gas bubbles and fountains from Crater Lake, he said.
But despite the low warning level - the mountain's alert level is still only set to level one out of five - the signals were similar to those prior to last September's eruption which left Auckland school teacher William Pike trapped in a hut struck by falling rocks.
Mr Pike was rescued from the Dome Hut near Ruapehu's summit but suffered serious injuries and had part of his leg amputated.
Dr Hurst said despite the low risk of such an event happening again this year, Ruapehu was an unpredictable and restless volcano.
"We don't really know what's happening under there. The amount of gas has increased a bit, but these things go up and down on a continual basis.
"We're just sort of reminding people that it does sometimes have eruptions with very little warning."
While the current 35C temperature of Crater Lake was slightly high, it was still within the lake's normal range, he said. The lake could get as hot as 60C.
While the lake's temperature was appealing, volcanic activity meant its sulphuric acid levels were too high to allow people to swim in it. Swimming in the Crater Lake was common until the 1950s, he said.
