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Supervolcano eruption mystery solved

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If the Yellowstone supervolcano erupted the impact would be catastrophic

Supervolcanoes like Yellowstone can explode without an earthquake or other external trigger, experts have found.

The sheer volume of liquid magma is enough to cause a catastrophic super-eruption, according to an experiment at the European Synchrotron Radiation Facility (ESRF) in Grenoble.

Simulating the intense heat and pressure inside these “sleeping giants” could help predict a future disaster.

The study by a Swiss team from ETH Zurich appears in Nature Geoscience.

Lead author Wim Malfait, of ETH Zurich said: “We knew the clock was ticking but we didn’t know how fast: what would it take to trigger a super-eruption?

“Now we know you don’t need any extra factor – a supervolcano can erupt due to its enormous size alone.

“Once you get enough melt, you can start an eruption just like that.”

There are about 20 known supervolcanoes on Earth – including Lake Toba in Indonesia, Lake Taupo in New Zealand, and the somewhat smaller Phlegraean Fields near Naples, Italy.

Super-eruptions occur rarely – only once every 100,000 years on average. But when they do occur, they have a devastating impact on Earth’s climate and ecology.

When a supervolcano erupted 600,000 years ago in Wyoming, in what today is Yellowstone National Park, it ejected more than 1,000 cubic km of ash and lava into the atmosphere – enough to bury a large city to a depth of a few kilometres.

Lake Toba in Sumatra was formed during the eruption of a supervolcano 74,000 years ago

This ejection was 100 times bigger than Mt Pinatubo in the Philippines in 1992 and dwarfs even historic eruptions like Krakatoa (1883).

“This is something that, as a species, we will eventually have to deal with. It will happen in future,” said Dr Malfait.

“You could compare it to an asteroid impact – the risk at any given time is small, but when it happens the consequences will be catastrophic.”

Being able to predict such a catastrophe is obviously critical. But the trigger has remained elusive – because the process is different from conventional volcanoes like Pinatubo and Mt St Helens.

One possible mechanism was thought to be the overpressure in the magma chamber generated by differences between the less dense molten magma and more dense rock surrounding it.

“The effect is comparable to holding a football under water. When you release it, the air-filled ball is forced upwards by the denser water around it,” said Wim Malfait, of ETH Zurich.

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The Earth is Grumbling

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Argentina and Chile order evacuation of Copahue volcano

Residents living near Copahue were also evacuated last year after the volcano erupted (file picture)

Chile and Argentina have ordered the evacuation of some 3,000 people living near the Copahue volcano in the south of their shared border.

The authorities in both countries issued a red alert – the highest possible – saying the Chilean volcano could erupt imminently.

The 2,965m (nearly 10,000ft) volcano – which sits in the Andes cordillera – has so far only spewed gas.

Thousands of minor earth tremors have been registered in the area.

“This red alert has been issued after monitoring the activity of the volcano and seeing that it has increased seismic activity,” Chilean Interior Minister Andres Chadwick said in a news conference.

“There is a risk that it can start erupting.”

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New Icelandic volcano eruption could have global impact

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Ford Cochran says that the 500 or so tremors in and around the caldera of Katla just in the last month suggest "an eruption may be imminent"

Hundreds of metres under one of Iceland’s largest glaciers there are signs of a looming volcanic eruption that could be one of the most powerful the country has seen in almost a century.

Mighty Katla, with its 10km (6.2 mile) crater, has the potential to cause catastrophic flooding as it melts the frozen surface of its caldera and sends billions of gallons of water surging through Iceland’s east coast and into the Atlantic Ocean.

“There has been a great deal of seismic activity,” says Ford Cochran, the National Geographic’s expert on Iceland.

There were more than 500 tremors in and around the caldera of Katla just in October, which suggests the motion of magma.

“And that certainly suggests an eruption may be imminent.”

Scientists in Iceland have been closely monitoring the area since 9 July, when there appears to have been some sort of disturbance that may have been a small eruption.

Eruption ‘long overdue’?

Even that caused significant flooding, washing away a bridge across the country’s main highway and blocking the only link to other parts of the island for several days.

“The 9 July event seems to mark the beginning of a new period of unrest for Katla, the fourth we know in the last half century,” says Professor Pall Einarsson, who has been studying volcanoes for 40 years and works at the Iceland University Institute of Earth Sciences.

“The possibility that it may include a larger eruption cannot be excluded,” he continues. “Katla is a very active and versatile volcano. It has a long history of large eruptions, some of which have caused considerable damage.”

The last major eruption occurred in 1918 and caused such a large glacier meltdown that icebergs were swept into the ocean by the resulting floods.

The volume of water produced in a 1755 eruption equalled that of the world’s largest rivers combined.

Thanks to the great works of historic literature known as the Sagas, Iceland’s volcanic eruptions have been well documented for the last 1,000 years.

But comprehensive scientific measurements were not available in 1918, so volcanologists have no record of the type of seismic activity that led to that eruption.

All they know is that Katla usually erupts every 40 to 80 years, which suggests the next significant event is long overdue.

Eyjafjallajokull's relatively small eruption in 2010 halted air traffic across Europe.

Katla is part of a volcanic zone that includes the Laki craters. In 1783 volcanoes in the area erupted continuously for eight months, generating so much ash, hydrogen fluoride and sulphur dioxide that it killed one in five Icelanders and half of the country’s livestock.

“And it actually changed the Earth’s climate,” says Mr Cochran.

“Folks talk about a nuclear winter – this eruption generated enough sulphuric acid droplets that it made the atmosphere reflective, cooled the planet for an entire year or more and caused widespread famine in many places around the globe.

“One certainly hopes that Katla’s eruption will not be anything like that!”

The trouble is scientists do not know what to expect. As Prof Einarsson explains, volcanoes have different personalities and are prone to changing their behaviour unexpectedly.

“When you study a volcano you get an idea about its behaviour in the same way you judge a person once you get to know them well.

Source: BBC News Read more

Another Riddle Solved

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