Mt Ruapehu eruption in 1995. Photo / File
By Mary Argue of RNZ
Thirty years ago on Tuesday, Mt Ruapehu exploded in spectacular fashion, triggering headlines overseas and a somewhat haphazard emergency response at home.
Scientists who were there say it was good luck – not good management – that no one was killed.
The volcano in the central plateau had been rumbling away for months, when in September 1995 it blew – sending lahars thundering down valleys and plumes of smoke and volcanic ash kilometres into the sky.
It sparked the start of unrest that would last until mid-1996, with the eruptions costing the local economy millions in tourism dollars.
According to the Natural Hazards Commission (NHC), the acidic ash that spewed into the air caused havoc – blanketing areas up to 300km downwind and intermittently closing highways and airports, shorting power pylons and damaging the turbines at Rangipō power station.
Agriculture also took a hit, with ash damaging crops and killing about 2000 sheep grazing on ash-covered pastures. The NHC said it also led to a “small but notable increase in bronchitis”.
The most powerful eruption on September 23, sent a column of smoke and debris 12km high, and rocks 1.5km from the crater.
While skiers dropped their gear and fled, others went towards it, including NHC chief resilience and research officer Jo Horrocks, who was then a student volcanologist.
“The ash cloud was coming over the top of us and the whole sky just looked black, it was dark.
“It was difficult to breathe because the ash was just everywhere. You were just in a cloud of ash as it was raining down on you.”
When it became clear it was too dangerous on the Whakapapa ski field, Horrocks went to Tūroa, on the other side, where a now iconic looking photo of her was taken as the volcano rumbled beneath her.
“Little tremors and then big booming noises when the big explosions happened – really big – and [I was] just struck with the absolute power of nature.
“It was the single best day of my life.”
Earth Sciences volcanologist Brad Scott was also in the area that week, taking samples on the mountain in between eruptions – something he suspected health and safety would never allow these days.
But back then, organisations were scrambling, he said, as they reacted to the biggest volcanic activity – and ash plume – in 50 years.
“All of a sudden, people in agriculture, aviation, and transport and health and emergency management had to start thinking, ‘Oh god, how do I play this game?’
“There were no significant injuries, and certainly nobody was killed. There was probably a lot of luck at that time, rather than good management.”
Scott said research and monitoring had come a long way since, and scientists now believe a pulse of heat in the lake as far back as December 1994 was likely the first sign of an impending eruption.
“Back then if you had a map with dots on it representing where we’re collecting data and [compared it to] today’s map, the number of dots hasn’t changed significantly but what is represented by the dot has changed really dramatically.
“The types of equipment at the locations - that is significantly different.”
He said the rudimentary warning systems for lahars and managing the public had matured enormously, as well as scientists’ understanding of volcanic hazards, such as ballistics or volcanic cannon balls, which can be hurled kilometres in an eruption.
It wasn’t a coincidence, he said, that there was no infrastructure within 4km of a volcanic vent.
These days, Scott said monitoring of earthquakes, lake temperature, volcanic chemistry and gas emissions, all fed into volcanic alerts and bulletins that could trigger a range of responses from organisations such the Department of Conservation, police, transport and civil defence.
Horrocks said the emergency response in 1995-96, compared to what would happen today, was like “night and day”.
“With all due respect to responding agencies and scientists at the time, there was a lot of making it up as we went back then.”
She said the connections between the response, science, and infrastructure organisations – sparked by the unrest 30 years ago – were now well-established.
“I would very much hope ... that we would be in fairly good stead if something happened in the future.”
A scenario that, according to Scott, is likely given Mt Ruapehu is an active volcano.
“Volcanoes are very good at putting their hand up, just how high they have their hand up, and how they’ve put it up is the challenge.”
- RNZ