A stranger helped a woman who was injured when a tumbling boulder bowled into her on a steep-sided mountain.
The Taupo-based Greenlea Rescue Helicopter helped rescue the woman from Mt Ngauruhoe yesterday morning.
Pilot Nat Every said the young woman landed in trouble "through no fault of her own" and received hand and leg injuries.
Mr Every said another woman who'd been walking up Ngauruhoe stayed with the victim until rescue crews arrived.
Ruapehu Alpine Rescue team members flew to help the young woman and loaded her into the hovering helicopter.
It was far too steep to land on the rocky mountain, Mr Every said.
He said the injured woman had a good prognosis but it would've likely been a "pretty scary" experience for her.
Mr Every said it was "totally random but not uncommon" for boulders to tumble down and knock into people climbing the mountain.
"Once you've been up the side of a very steep mountain it's something more daunting than a lot of people would [imagine]."
Mr Every said the woman had been walking on the most popular route up the 2291m-high volcano.
He said the track was fairly busy and sometimes descending climbers accidentally dislodged small boulders.
"Take care not to gather too much speed, it is easy to trip and there is a long way to fall - and many sharp rocks to hit," the Department of Conservation (DoC) advised climbers.
DoC said good fitness was needed to climb Ngauruhoe, a rugged active stratovolcano.
The injured woman was flown to Taupo Hospital.