Sat, Dec 27, 2003 - Page 16 News List

Killer mountain still haunts New Zealand

Mount Ruapehu erupted in 1995 causing one of the country's biggest natural disasters -- and it's threatening to blow its top again


Mount Ruapehu is showing signs of erupting once more.


Fifty years after it spilled a lethal mix of mud, ash and water which washed away a bridge and derailed a train, killing 151 people, Mount Ruapehu, at 2,797 metres the highest peak in New Zealand's North Island, is threatening to do it again.

As the nation remembers the tragedy of Christmas Eve 1953 when Ruapehu, an active volcano, created one of the country's worst ever natural disasters, controversy has broken out about how to prevent the loss of lives next time and minimize the damage.

Mount Ruapehu contains a steaming 17-hectare lake in a crater near the summit which burst through the ice wall rim on Dec. 24, 1953 sending a lahar (a silt and rock-laden mudflow) down the mountainside and sweeping away the Tangiwai rail bridge minutes before the Wellington to Auckland night express roared through.

The engine and first five carriages were picked up by the unstoppable tide of swirling mud and rock and carried four kilometres down the Whangaehu River, killing 151 of the 285 people aboard and indelibly etching Tangiwai (Maori for "weeping waters") into the national consciousness.

It was the most devastating of the 60 or so lahars that have swept down the slopes of Ruapehu over the last 150 years.

It had not been predicted, though it followed a series of eruptions eight years earlier which emptied the crater lake and dammed its outlet with rocks and glacial ice allowing it to refill to a much greater depth than before.

In 1995, the mountain erupted again, emptying out the crater lake once more. It left a dam about 7m thick over its former outlet, but this time there is no ice content and geologists say the wall is weak.

The lake is refilling and barring another eruption, the boiling hot water is expected to reach the top of the dam within the next two years.

Another runaway lahar would damage the new road and rail bridges at Tangiwai and block State Highway 1 between the capital Wellington and the country's biggest city and commercial center Auckland.

Some want the government to construct a channel to allow the lake to be safely drained into the Whangaehu River and out to sea before it breaks through the top of the rim and creates a lahar.

But instead, the government has chosen an early warning system that is designed to give 90 minutes' notice of a lahar heading toward the bridges and an hour to stop traffic entering the part of the highway that would lie in its path.

It is also building a bund, or stopbank, to divert the lahar from the ecologically sensitive Tongariro River, a popular trout fisherman's waterway.

There are other issues. Ruapehu is one of several volcanoes in the central North Island, all revered by local Maori tribes for their spiritual and cultural links with ancestors and gods.

They oppose any artificial alteration of the mountain as an insult to their ancestors.

In addition, the volcanoes are all in the Tongariro National Park, one of only a score or so sites in the world with dual World Heritage status in recognition of outstanding natural and cultural values.

The government fears interfering with Ruapehu's crater lake could compromise that status.

Former Minister of Conservation Nick Smith says the government's sensitivity over Maori spiritual values and its aversion to doing earthworks in the National Park have led to the rejection of a "commonsense solution" to excavate the dam.

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