Archive for the ‘supervolcano’ Category

by ROBERT KRULWICH

Add all of us up, all 7 billion human beings on earth, and clumped together we weigh roughly 750 billion pounds. That, says Harvard biologist E.O. Wilson, is more than 100 times the biomass of any large animal that’s ever walked the Earth. And we’re still multiplying. Most demographers say we will hit 9 billion before we peak, and what happens then?

Well, we’ve waxed. So we can wane. Let’s just hope we wane gently. Because once in our history, the world-wide population of human beings skidded so sharply we were down to roughly a thousand reproductive adults. One study says we hit as low as 40.

Forty? Come on, that can’t be right. Well, the technical term is 40 “breeding pairs” (children not included). More likely there was a drastic dip and then 5,000 to 10,000 bedraggled Homo sapiens struggled together in pitiful little clumps hunting and gathering for thousands of years until, in the late Stone Age, we humans began to recover. But for a time there, says science writer Sam Kean, “We damn near went extinct.”

I’d never heard of this almost-blinking-out. That’s because I’d never heard of Toba, the “supervolcano.” It’s not a myth. While details may vary, Toba happened.

Toba, The Supervolcano

Once upon a time, says Sam, around 70,000 B.C., a volcano called Toba, on Sumatra, in Indonesia went off, blowing roughly 650 miles of vaporized rock into the air. It is the largest volcanic eruption we know of, dwarfing everything else…

That eruption dropped roughly six centimeters of ash — the layer can still be seen on land — over all of South Asia, the Indian Ocean, the Arabian and South China Sea. According to the Volcanic Explosivity Index, the Toba eruption scored an “8”, which translates to “mega-colossal” — that’s two orders of magnitude greater than the largest volcanic eruption in historic times at Mount Tambora in Indonesia, which caused the 1816 “Year Without a Summer” in the northern hemisphere.

With so much ash, dust and vapor in the air, Sam Kean says it’s a safe guess that Toba “dimmed the sun for six years, disrupted seasonal rains, choked off streams and scattered whole cubic miles of hot ash (imagine wading through a giant ashtray) across acres and acres of plants.” Berries, fruits, trees, African game became scarce; early humans, living in East Africa just across the Indian Ocean from Mount Toba, probably starved, or at least, he says, “It’s not hard to imagine the population plummeting.”

Then — and this is more a conjectural, based on arguable evidence — an already cool Earth got colder. The world was having an ice age 70,000 years ago, and all that dust hanging in the atmosphere may have bounced warming sunshine back into space. Sam Kean writes “There’s in fact evidence that the average temperature dropped 20-plus degrees in some spots,” after which the great grassy plains of Africa may have shrunk way back, keeping the small bands of humans small and hungry for hundreds, if not thousands of more years.

So we almost vanished.

But now we’re back.

It didn’t happen right away. It took almost 200,000 years to reach our first billion (that was in 1804), but now we’re on a fantastic growth spurt, to 3 billion by 1960, another billion almost every 13 years since then, till by October, 2011, we zipped past the 7 billion marker, says writer David Quammen, “like it was a “Welcome to Kansas” sign on the highway.”

In his new book Spillover, Quamman writes:

We’re unique in the history of mammals. We’re unique in this history of vertebrates. The fossil record shows that no other species of large-bodied beast — above the size of an ant, say or an Antarctic krill — has ever achieved anything like such abundance as the abundance of humans on Earth right now.
But our looming weight makes us vulnerable, vulnerable to viruses that were once isolated deep in forests and mountains, but are now bumping into humans, vulnerable to climate change, vulnerable to armies fighting over scarce resources. The lesson of Toba the Supervolcano is that there is nothing inevitable about our domination of the world. With a little bad luck, we can go too.

We once almost did.

http://www.npr.org/sections/krulwich/2012/10/22/163397584/how-human-beings-almost-vanished-from-earth-in-70-000-b-c

Researchers claim to have worked out how to accurately predict the eruption of ‘supervolcanoes’ that blanket the earth in giant ash clouds triggering a ‘nuclear winter’.

They say the discovery could reveal exactly when giant pools of magma greater than 100 cubic miles in volume and formed a few miles below the surface will erupt.

Repeatedly throughout Earth’s history,when they become a super-eruption, the resulting gigantic volcanic outbursts that throw 100 times more superheated gas, ash and rock into the atmosphere than run-of-the-mill eruptions – enough to blanket continents and plunge the globe into decades-long volcanic winters.

The most recent super-eruption took place about 27,000 years ago in New Zealand, well before humans kept records of volcanic eruptions and their aftermath.

Geologists today are studying deposits from past super-eruptions to try and understand where and how rapidly these magma bodies develop and what causes them to eventually erupt.

Despite considerable study, geologists are still debating how quickly these magma pools can be activated and erupted, with estimates ranging from millions to hundreds of years.

Now a team of geologists have developed a new ‘geospeedometer’ that they argue can help resolve this controversy by providing direct measurements of how long the most explosive types of magma existed as melt-rich bodies of crystal-poor magma before they erupted.

They have applied their new technique to two super-eruption sites and a pair of very large eruptions and found that it took them no more than 500 years to move from formation to eruption.

These results are described in the article ‘Melt inclusion shapes: Timekeepers of short-lived giant magma bodies’ appearing in the November issue of the journal Geology.

Geologists have developed a number of different ‘timekeepers’ for volcanic deposits.

The fact that these techniques measure different processes and have different resolutions, has contributed to this lack of consensus.

‘Geologists have developed a number of different ‘timekeepers’ for volcanic deposits,’ said Guilherme Gualda, associate professor of earth and environmental sciences at Vanderbilt University, who directed the project.

‘The fact that these techniques measure different processes and have different resolutions, has contributed to this lack of consensus.

‘Our new method indicates that the process can take place within historically relevant spans of time,’
The method was developed as part of the doctoral thesis of Ayla Pamukcu, who is now a post-doctoral researcher at Brown and Princeton Universities.

‘The hot spot under Yellowstone National Park has produced several super-eruptions in the past.

‘The measurements that have been made indicate that this magma body doesn’t currently have a high-enough percentage of melt to produce a super-eruption.

But now we know that, when or if it does reach such a state, we will only have a few hundred years to prepare ourselves for the consequences,’ Gualda said.

The researchers’ geospeedometer is based on millimeter-sized quartz crystals that grew within the magma bodies that produced these giant eruptions.

Quartz crystals are typically found in magmas that have a high percentage of silica.

This type of magma is very viscous and commonly produces extremely violent eruptions. Mount St. Helens was a recent example.

When the crystals form, they often capture small blobs of molten magma – known as blebs or melt inclusions. Blebs are initially round.

While the crystal is floating in hot magma, diffusion causes them to gradually acquire the polygonal shape of the crystal void that they occupy. But this faceting process can be halted if eruption occurs before complete faceting is achieved.

Using advanced 3-D X-ray tomography, the researchers were able to measure the size and shape of the melt inclusions with exquisite precision.

In cases where the inclusions had not become completely faceted, the researchers could determine how much time had elapsed since they were enclosed.

‘Previous studies provided us with the data we needed to calculate the rate of the faceting process. We then used this rate, in combination with our shape measurements, to calculate how long the crystal existed in the magma before the eruption,’ said Pamukcu.

In addition, the researchers compared the results obtained with faceting with results obtained using other techniques.

Crystallization may cause variations in concentration of certain elements. In quartz, the element titanium can vary sharply between different zones or layers within the crystal.

Over time, however, the process of diffusion gradually smooths out these variations.

This process also stops at the eruption, so the shallower the slope of titanium concentrations across these boundaries today, the longer the crystal spent in magmatic conditions.

The physics of this process is also well known, so the researchers could use these measurements to provide an independent estimate of how long a crystal spent floating around in the melt.

They found that the duration times they derived from the titanium diffusion measurements agreed closely with those produced by the faceting method.

‘Our current method will also work on smaller volcanic systems, as long as they erupt magmas that contain quartz crystals,’ said Pamukcu.

‘We are also confident that we can adapt these techniques to work with other minerals, which will allow us to make similar timescale calculations for other types of magmas and volcanoes, like the low-silica basalts commonly erupted from Hawaiian volcanoes.’

Read more: http://www.dailymail.co.uk/sciencetech/article-3281859/Phew-Scientists-claim-developed-predict-cataclysmic-SUPERVOLCANO-eruptions-end-life-Earth.html#ixzz3pD81J9cT

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Tourists at Yellowstone National Park are being barred from areas of the park because the massive underground supervolcano beneath it is melting the asphalt roads.

“It basically turned the asphalt into soup. It turned the gravel road into oatmeal,” Yellowstone spokesman Dan Hottle said. In particular, Hottle said that the road between the park’s most popular attraction, Old Faithful, and Madison Junction has been dangerously compromised.

Park officials also asked tourists not to hike into the affected areas, as the danger of stepping through what appears to be solid soil into boiling-hot water was “high.”

There are plenty of other great places to see thermal features in the park,” park spokesman Al Nash told The Weather Channel. “I wouldn’t risk personal injury to see these during this temporary closure.”

It is not known when the road, which services the three million people who visit the park every year, will be reopened.

The last time the supervolcano beneath Yellowstone actually erupted was 640,000 years ago, U.S. Geological Survey records show.

Late last year, geologists discovered that the supervolcano was more than twice as large as previously thought.

“We found it to be about two-and-a-half times larger than we thought,” the University of Utah’s James Farrell told National Geographic. “That’s not to say it’s getting any bigger,” he added, “just that our ability to see it is getting better.”

Thanks to Ray Gaudette for bringing this to the attention of the It’s Interesting community.

http://www.rawstory.com/rs/2014/07/14/parts-of-yellowstone-national-park-closed-after-massive-supervolcano-beneath-it-melts-roads/?onswipe_redirect=no&oswrr=1