Posts Tagged ‘ruapehu’

Tongariro-August-2012-New-Zealand

Mt Tongariro – long considered a peaceful neighbour to the rowdy Ruapehu – is much more fiery than we ever realised, says a scientist sharing new findings today.

GNS Science volcanologist Brad Scott, among scientists giving presentations in a workshop at Whakapapa Village, has found evidence of eruptions at Mt Tongariro that weren’t previously on the records.

Tongariro’s dramatic eruptions in August and November of 2012 transformed our understanding of what had been considered a comparatively docile mountain, Mr Scott said.

When ash shot from the Te Maari Crater 7km into the sky shortly before midnight on August 6, it was thought at the time to have been the first blow there since 1896.

But Mr Scott has since found records indicating an eruption at the crater in 1928, with other events at Red Crater – a feature of the Tongariro Alpine Crossing – in 1909, 1926, 1927 and 1934. Further, there was volcanic unrest at the mountain right up until the 1970s, he said.

“We all knew Ruapehu and Ngauruhoe were pretty busy but, until now, nobody really perceived Tongariro as being as active as it has been.”

The new information, with the 2012 eruptions, had led to a range of new protocols and emergency policies at the peak, including warning systems and more public information. “[And] we’ve upgraded monitoring equipment in the area and have put in place more seismographs.”

Other research being presented would discuss findings around the ballistics of rocks that were ejected from the mountain in 2012, as well as the volcanic avalanches and debris flows that came with the eruption.

Mr Scott saw the event as a success story because authorities had been able to warn residents after monitoring picked up elevated activity.

Today’s workshop will kick off a weekend reflecting on the 20th anniversary of the 1995-96 eruptions of Mt Ruapehu. This year also marks the 40th anniversary of the 1975 Ngauruhoe eruption and the 70th anniversary of the 1945 Ruapehu eruption.

Mt Ruapehu eruptions: 20 years on

• The 1995-96 eruptions ejected a total of 60 million cubic metres of acidic ash – blanketing districts up to 300km from the mountain, irritating eyes and throats in the central North Island, damaging car paintwork and machinery, contaminating rivers and water supplies, ruining crops, closing state highways, forcing airports to shut and killing livestock which ate ash-covered pastures.

• Electricity suppliers were hit with multimillion-dollar losses as ash shorted out power pylons and severely damaged turbines in the Rangipo power station. At times the ash plume reached as high at 10km, which represented a significant aviation hazard.

• The eruptions were similar in size to those in 1945, but their social and economic impacts were much greater. In 1945 there was just one ski area and no ski lifts on Ruapehu. By 1995, there were three ski areas and 36 ski lifts. By the mid-90s there were up to 10,000 people on the mountain on some days during winter.

– NZ Herald

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Te Maari Crater eruption on Mt Tongariro. Photo / Ben Fraser

The steam and super-heated gases which have been pouring from the side of Mt Tongariro since its two surprise eruptions last year are set to be a feature of the volcano for years.

And nearly two months since Mt Tongariro last blew, GNS volcanologists say there’s every chance of another sudden eruption, just as at neighbouring Mt Ruapehu and White Island to the north.

[Read More – New Zealand Herald]

Volcano watch

White Island
This week downgraded from alert level two to one (out of five). A recently-established lava dome has stopped growing, but scientists say a column of magma not far beneath still poses a threat.

Mt Ruapehu
Remains at alert level one with an exclusion zone around the summit. A suspected blockage below the crater lake may be causing a gas build up that could result in sudden eruption.

Mt Tongariro
Remains at alert level one with part of the Tongariro Alpine Crossing closed. Emitting large amounts of gas and sulphur dioxide and scientists still expect a repeat of the last eruption in November.

The eruption of Ruapehu, June 1996.

Just like Mt Tongariro’s surprise bang on Wednesday afternoon, what happened a few kilometres away at 8.20pm on September 25, 2007, came suddenly and violently.

Shortly before airline pilots noticed a black plume rising above Mt Ruapehu, a volcanic blast threw ash, rocks and water across the summit area, sending two muddy torrents down the skifields.

Inside a hut on the edge of the crater lake, William Pike and James Christie heard a “massive boom” before the building’s door was blown from its hinges and mud and rock poured inside. Mr Pike’s crushed leg later had to be amputated.

The warning signs Mt Ruapehu gave in the days before that explosive moment are being seen again now – worrying scientists that the mountain could be about to produce a similar-sized eruption.

GNS volcanologist Michael Rosenberg said Mt Ruapehu has been showing two forms of unrest, which are considered unrelated.

There have been 45 earthquakes about 5km beneath the mountain since early August, but 35 of those have come in the past month.

[Read More – NZ-Herald]

 

The last eruption at Mt Ruapehu was in 2007. It was also thought to have been caused by a build-up of pressure beneath crater lake. Photo / Nicola Topping

Scientists are warning there are heightened signs of volcanic activity at Mt Ruapehu and an eruption could be just weeks away.

GNS Science experts say pressure is building up in the crater lake at the volcano and there is now a high risk of an eruption.

Volcanologist Steven Sherburn said: “We think that the temperature a few hundred metres beneath crater lake is about 800C, but the lake itself is only about 20C.

“This suggests the vent is partly blocked, which may be leading to a pressure build-up beneath crater lake. A sudden release of the pressure may lead to an eruption.”

[Read More – NZ Herald]

 

 

The blackened crater of Mt Ruapehu after it erupted in 2007. Photo / John Cowpland

The blackened crater of Mt Ruapehu after it erupted in 2007. Photo / John Cowpland

 

The likelihood of Mt Ruapehu erupting has increased, GNS Science says.

GNS Science duty volcanologist Steven Sherburn said changes in measurements at Ruapehu over the last few weeks indicate eruptions are “more likely over the next weeks to months”.

“We are monitoring Ruapehu closely, but it often does not give any immediate warning that it is going to erupt,” Dr Sherburn said.

“We think that the temperature a few hundred metres beneath Crater Lake is about 800 degrees Celsius, but the lake itself is only about 20 degrees Celsius. This suggests the vent is partly blocked which may be leading to a pressure build-up beneath Crater Lake.

“A sudden release of the pressure may lead to an eruption.”

As a result, the Aviation Colour Code has increased from Green to Yellow. However, the Volcanic Alert Level remains at 1. Code Yellow indicates a volcano is experiencing signs of elevated unrest above known background levels.

GNS said small earthquakes have been occurring about 5km beneath the summit area of Ruapehu since late-October, but these may not be directly related to the high temperatures beneath Crater Lake as the earthquakes are much deeper.

A build-up of pressure beneath Crater Lake is thought to have caused the 2007 eruption and a smaller eruption in 2006.

Source – nzherald.co.nz