Volcanologists move to counter Mt Ruapehu myths and public misconception

Thursday, 12 May 2016

The threat from Mt Ruapehu

Volcanologists have moved to counter some of the more common Mt Ruapehu myths and public misconceptions around seismic activity in New Zealand.

The volcanic alert level for Mt Ruapehu in Tongariro National Park was raised to level two on Wednesday.

An aviation warning was also raised from green to yellow to mark signs of volcanic unrest.

Mt Ruapehu has been showing signs of activity and the crater lake temperature has risen by more than 20C.

White Island's volcanic alert level was downgraded to level one, after an eruption on April 27, but volcanologists continue to monitor the Bay of Plenty privately-owned island.

**READ MORE:

The White Island crater was showered with green ash by the eruption.

* More activity but eruption unlikely at Ruapehu

* Hot ash surged quickly across White Island**

Geonet constantly monitors the crater lake and the volcano, where a swarm of tremors was recorded during April at Ruapehu, the largest active volcano in New Zealand and the highest North Island peak, rising to 2797 metres at the southern end of the Taupo volcanic zone.

Ruapehu and White Island, while situated on the same tectonic system, are not linked.

The Ruapehu crater lake has been rising in temperature since mid-April and shot up from 25C to 46C. This action, which takes place in cycles of heating and cooling, is typical and, since 2010, eight such cycles have been recorded.

Mt Ruapehu erupted during 1995 and 1996.

Geonet volcanologist Brad Scott said there was a lot of public misconception about the volcano in Tongariro and on White Island.

While there was an increase in seismic activity and increases in the amount of carbon dioxide and sulphur dioxide output by Ruapehu, there was no immediate risk for people who want to use the national park.

And there was no connection between White Island, 50km off the east coast, and Mt Ruapehu, in the central North Island.

'There's a lot of public misconception that it's dangerous to go [to Tongariro].

'It's a great place and it's safe to go there.'

Volcanic conditions were comparable to the late 1960s and 1970s, when the crater lake temperature reached 52degC, he said.

Significant eruptions, although these were not classed as 'major' events, happened in 1967, 1971 and 1975.

The highest recorded crater lake temperature was 60degC in 1968.

'One of the common factors of the crater lake is it heats up and cools down. Typically those cycles last between nine and 14 months.

'The heating pattern is pretty typically around 1C per day or thereabouts. The sort of heating in the last three weeks is the same rate of heating as we always see.

'We are seeing more signs of life at the volcano but when there's unrest that doesn't always lead to an eruption. It can show more signs of life and then go back to a quieter state.'

Mt Tongariro and the Tongariro Alpine Crossing are not affected by the current activity.

'One of the points is that the alert level has gone up but it doesn't mean you have to avoid the national park.

'I'm quite comfortable saying the public are safe in all of the normally accessible parts of the park.

'There have been several heating cycles since 2010, none of which culminated in eruption activity,' Scott said.

A Department of Conservation warning was issued on Wednesday, recommending trampers and guiding companies avoid the summit zone.

The greatest risk from the volcano is a lahar, a mudflow often stemming from a crater wall collapse.

The department, unable to ban people from using a national park, recommended avoiding the 'summit hazard zone,' a two-kilometre area with the crater at its centre.

Department volcanology technical advisor Dr Harry Keys said the poor weather was keeping people away from the mountain, although during previous eruptions there had been instances of visitors and residents venturing towards an eruption.

'They are both [White Island and Ruapehu] really active volcanoes.

'The law of averages says they are both active at the same time at some point. But people only notice when they are active together.'

A Ruapehu crater climb was popular and fantastic place to experience a volcanic crater in an alpine zone, one of the few such accessible places in the world.

The framework around New Zealand conservation regulations, national park jurisdictions and land rights mean, in most cases, people cannot be prohibited from entry.

Keys said the department maintained a high level of preparedness around Ruapehu and the Tongariro National Park.

On Wednesday, department operations manager for Tongariro Paul Carr recommended climbers, trampers and guiding companies do not enter the upper zone.

Historically, major eruptions have been about 50 years apart, in 1895, 1945 and the last significant eruption in 1995.

Around 60 smaller eruptions have occurred since 1945.

Scientists believe a series of small, linked magma chambers lie between one and five kilometres below the crater.

White Island was also showing more signs of activity, but it was important to remember the volcano has been active since 1975, Scott said.

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