Fears of pending Mt Ruapehu eruption dismissed

Mt Ruapehu live cam image. Photo / Institute of Geological and Nuclear Sciences.

Mt Ruapehu isn't erupting, nor is it even letting off much in the way of steam, but people have been reporting otherwise and a scientist thinks he knows why.

GNS Science duty volcanologist Michael Rosenberg has even risked his own body to test his theories.

He says a combination of cold still air and warm water has made the crater lake on Mt Ruapehu look like it's steaming.

Pilots have noticed the steam in recent days. Air Chathams passengers on a return flight to Whanganui from Auckland were invited to look out their windows to witness the steam rising out of the mountain.

But Rosenberg says the lake is just 33degC and eruption alert levels are normal.

"We had scientists up there earlier this morning, collecting water samples, and there's no eruptive activity at all and nothing to be alarmed about."

If you were to put your hand in that it will tingle, but it wouldn't blister and peel your skin. I know, because I've tried it

The lake goes through unpredictable heating and cooling cycles, Rosenberg said. For the last 10 years its top temperature has been just above 40degC.

Between heating periods it cools to 10 to 12degC - but it hasn't got that low during the last two years.

"We have only had high 20s, before it starts to heat up again."

Scientists continually monitor the lake's water and gas. They notice any increase in water level that can't be explained by the addition of rain or melting snow.

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Just recently its level has been high enough to overflow a little, into the Whangaehu River.

Generally, water in the lake is the temperature of a tepid bath, and has an acidity level similar to that of a car battery.

GNS Science duty volcanologist Michael Rosenberg.

"The acidity is less than pH1. If you were to put your hand in that it will tingle, but it wouldn't blister and peel your skin. I know, because I've tried it," Rosenberg said.

The reported activity comes two weeks after the death of 32-year-old Magesh Jagadeesan from Lower Hutt who died after falling into Crater Lake on Mt Ruapehu.

His death lead iwi to place a sacred rāhui on the area.

High risk warning after man dies falling into Mt Ruapehu's crater lake

To show respect, all climbers, trampers and skiers were asked not to go above the boundaries of the ski areas at Whakapapa, Tūroa and Tukino, or above a line 2300-metre above sea level on the mountain.

The rāhui has since been lifted.

The Crater Lake on Mt Ruapehu where Magesh Jagadeesan died late last month.

In October 2017, New Zealand climber Richard Ebbett died after also falling into the crater lake.

Mt Ruapehu has had early snow as seen in this shot taken 29 May 2018.