Simmering NZ Crater Lake More Scary Than Mt. Doom
Mon May 3, 3:04 PM ET
By Marion Rae
WHAKAPAPA VILLAGE, New Zealand (Reuters) - New Zealand's Mount Ngauruhoe starred as fiery Mount Doom in Peter Jackson's epic film trilogy Lord of the Rings, but neighboring Mount Ruapehu is the volcano scientists fear most.
A trio of active volcanoes in the center of New Zealand's North Island -- Ngauruhoe, Ruapehu and Tongariro -- form the southern tip of the "Rim of Fire," an arc of active volcanoes circling the Pacific Ocean.
A simmering acidic crater lake on Mount Ruapehu, belching steam and gas that smells like rotten eggs, has been the site of more eruptions than any other crater lake in the world.
Scientists studying the lake say higher levels signal a greater chance of a mudflow, and warn that a disastrous mudslide could flow down the mountain some time between November this year and next March.
"It's a serious issue and it's preoccupied me for the past eight years," said Harry Keys, a volcanologist at New Zealand's Department of Conservation.
Mount Ruapehu's last major eruption was in June 1996. The crater lake erupted into billowing clouds of ash and steam with little warning -- less than 30 minutes after ski lifts had closed and less than 10 minutes after skiers left the crater lake's lip.
Located over the vent of the volcano and partially surrounded by permanent snow and ice, the Ruapehu's crater lake erupts every one to three years and was emptied in major eruptions in 1945 and 1995. Both times bridges were destroyed.
One of New Zealand's worst tragedies was in 1953 when the lake partially emptied on Christmas Eve, washing away a rail bridge at Tangiwai and killing 151 passengers and crew on board an express train.
"Tangiwai can't be allowed to happen again," said Keys.
RUMBLINGS
Snow-capped Ruapehu is inside the Tongariro National Park, about 186 miles north of the capital, Wellington. UNESCO (news - web sites) designated the park a World Heritage site in 1991.
Ruapehu, the North Island's highest peak, measures 9,173 feet. Its crater lake, with a temperature of about 86 degrees Fahrenheit despite its snow-capped rim, is close to the summit and contains about nine million cubic yards of water.
When the level of the lake, now about 95 percent full, rises another 16 feet it may break free, releasing a fast-moving wave with the consistency of wet cement.
Such an event is likely between November and March because while water levels in the lake are low in autumn and winter, during the warmer months the spring melt and rain drive up the levels.
Another trigger for a lahar -- an Indonesian word for a volcanic mudflow -- would be volcanic activity.
Ruapehu is showing some signs of volcano unrest, said the New Zealand Institute of Geological and Nuclear Sciences, with "elevated hydrothermal activity" in the crater lake.
Small high-frequency earthquakes beneath Ruapehu tapered off during Easter, followed by 12 hours of volcanic activity, and the volcano has been quiet since.
"That hazard is always there and many people seem to forget that," said Keys. "Eight years ago we had the biggest eruptions for 50 years and heaps of lahars, including ones that destroyed four bridges," he said.
COLLISION ZONE
New Zealand straddles a zone where the Indian-Australian and Pacific tectonic plates meet, causing the upper part of the North Island to slide away from the lower part of the South Island at a rate of about 13 feet every century.
Much of New Zealand was pushed up out of the sea as recently as 10,000 years ago, as the never-ending collision causes the landscape to buckle and rupture.
As the Pacific plate slides underneath the Indian-Australian plate, a hot spot of volcanic and thermal activity is created in the central North Island.
The plateau that dominates the island is home to a line of volcanoes and a deep crater now called Lake Taupo, a hole in the North Island as big as Singapore carved out by massive eruptions thousands of years ago.
The most recent eruption from Taupo, around AD 200, ejected clouds of dust that caused red sunsets seen as far away as the Roman and Chinese empires and was the world's biggest volcanic eruption in the last 5,000 years.
The best guess for the next Ruapehu lahar would be February 2005, and it is not possible to prevent them, said New Zealand's Department of Conservation.
But scientists are unable to narrow the likelihood of the event beyond a few months.
About 60 lahars have come down the side of Ruapehu in the past 150 years and the threat of another lahar is growing as the level of the crater lake rises toward the rim and threatens Whangaehu Valley on the flanks of Mount Ruapehu.
New Zealand's indigenous Maori people have long understood the mountain's behavior.
In the Maori language, "whanga" means large body of water and "ehu" means muddy -- reflecting how a history of lahars has provided the name for Whangaehu Valley, the most active lahar path in the world. Ruapehu translates as erupting crater.
"It's very predictable which way the lahar goes, it goes down the valley," said Keys. "It's going to be a serious hazard in the upper part of the valley."
Mon May 3, 3:04 PM ET
By Marion Rae
WHAKAPAPA VILLAGE, New Zealand (Reuters) - New Zealand's Mount Ngauruhoe starred as fiery Mount Doom in Peter Jackson's epic film trilogy Lord of the Rings, but neighboring Mount Ruapehu is the volcano scientists fear most.
A trio of active volcanoes in the center of New Zealand's North Island -- Ngauruhoe, Ruapehu and Tongariro -- form the southern tip of the "Rim of Fire," an arc of active volcanoes circling the Pacific Ocean.
A simmering acidic crater lake on Mount Ruapehu, belching steam and gas that smells like rotten eggs, has been the site of more eruptions than any other crater lake in the world.
Scientists studying the lake say higher levels signal a greater chance of a mudflow, and warn that a disastrous mudslide could flow down the mountain some time between November this year and next March.
"It's a serious issue and it's preoccupied me for the past eight years," said Harry Keys, a volcanologist at New Zealand's Department of Conservation.
Mount Ruapehu's last major eruption was in June 1996. The crater lake erupted into billowing clouds of ash and steam with little warning -- less than 30 minutes after ski lifts had closed and less than 10 minutes after skiers left the crater lake's lip.
Located over the vent of the volcano and partially surrounded by permanent snow and ice, the Ruapehu's crater lake erupts every one to three years and was emptied in major eruptions in 1945 and 1995. Both times bridges were destroyed.
One of New Zealand's worst tragedies was in 1953 when the lake partially emptied on Christmas Eve, washing away a rail bridge at Tangiwai and killing 151 passengers and crew on board an express train.
"Tangiwai can't be allowed to happen again," said Keys.
RUMBLINGS
Snow-capped Ruapehu is inside the Tongariro National Park, about 186 miles north of the capital, Wellington. UNESCO (news - web sites) designated the park a World Heritage site in 1991.
Ruapehu, the North Island's highest peak, measures 9,173 feet. Its crater lake, with a temperature of about 86 degrees Fahrenheit despite its snow-capped rim, is close to the summit and contains about nine million cubic yards of water.
When the level of the lake, now about 95 percent full, rises another 16 feet it may break free, releasing a fast-moving wave with the consistency of wet cement.
Such an event is likely between November and March because while water levels in the lake are low in autumn and winter, during the warmer months the spring melt and rain drive up the levels.
Another trigger for a lahar -- an Indonesian word for a volcanic mudflow -- would be volcanic activity.
Ruapehu is showing some signs of volcano unrest, said the New Zealand Institute of Geological and Nuclear Sciences, with "elevated hydrothermal activity" in the crater lake.
Small high-frequency earthquakes beneath Ruapehu tapered off during Easter, followed by 12 hours of volcanic activity, and the volcano has been quiet since.
"That hazard is always there and many people seem to forget that," said Keys. "Eight years ago we had the biggest eruptions for 50 years and heaps of lahars, including ones that destroyed four bridges," he said.
COLLISION ZONE
New Zealand straddles a zone where the Indian-Australian and Pacific tectonic plates meet, causing the upper part of the North Island to slide away from the lower part of the South Island at a rate of about 13 feet every century.
Much of New Zealand was pushed up out of the sea as recently as 10,000 years ago, as the never-ending collision causes the landscape to buckle and rupture.
As the Pacific plate slides underneath the Indian-Australian plate, a hot spot of volcanic and thermal activity is created in the central North Island.
The plateau that dominates the island is home to a line of volcanoes and a deep crater now called Lake Taupo, a hole in the North Island as big as Singapore carved out by massive eruptions thousands of years ago.
The most recent eruption from Taupo, around AD 200, ejected clouds of dust that caused red sunsets seen as far away as the Roman and Chinese empires and was the world's biggest volcanic eruption in the last 5,000 years.
The best guess for the next Ruapehu lahar would be February 2005, and it is not possible to prevent them, said New Zealand's Department of Conservation.
But scientists are unable to narrow the likelihood of the event beyond a few months.
About 60 lahars have come down the side of Ruapehu in the past 150 years and the threat of another lahar is growing as the level of the crater lake rises toward the rim and threatens Whangaehu Valley on the flanks of Mount Ruapehu.
New Zealand's indigenous Maori people have long understood the mountain's behavior.
In the Maori language, "whanga" means large body of water and "ehu" means muddy -- reflecting how a history of lahars has provided the name for Whangaehu Valley, the most active lahar path in the world. Ruapehu translates as erupting crater.
"It's very predictable which way the lahar goes, it goes down the valley," said Keys. "It's going to be a serious hazard in the upper part of the valley."
