Gigantic volcanic outbursts throw 100 times more superheated gas, ash and rock into the atmosphere than a normal eruption.
Can blanket continents and plunge globe into volcanic winters.
New technique can predict maegaquakes for first time.
It is a discovery that could save the life of million, and safeguard entire species.
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.
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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.
WHAT MAKES A MEGAERUPTION?
The most recent supervolcanic eruption on Earth occurred 27,000 years ago at Taupo located at the center of New Zealand's north island.
They occur when giant pools of magma greater than 100 cubic miles in volume form a few miles below the surface and erupt.
They 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.
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.
Quartz crystal that developed in molten magma. Black dots are blebs of molten rock captured in the crystal when it formed. Using advanced 3-D X-ray tomography, the researchers were able to measure the size and shape of the melt inclusions with unprecedented precision.
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.
The geologists use image process method that describe the edges of a melt inclusion by set of points. Next they use these points to create a 3-D polyhedron (red) that represents the final shape of the melt inclusion.
Once they have the final shape of the bleb, they create a 3D ellipsoid (blue) that represents its initial shape. Then they superimpose the two. The areas of the red polyhedron that extend beyond the surface of the ellipsoid represent the volume of the bleb that has migrated during the faceting process
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.
SCIENTISTS FIND MASSIVE NEW MAGMA CHAMBER UNDER YELLOWSTONE
In the heart of Yellowstone National Park, a supervolcano releases around 45,000 metric tonnes of carbon dioxide each day.
But the magma chamber lying directly beneath its surface is not considered large enough to produce such levels, so researchers have been searching for an alternative source for years.
In April, by tracking seismic waves, geophysicists discovered a huge secondary chamber deeper underground that's so large its partly-molten rock could fill the Grand Canyon 11 times over.
Previous research found a relatively small magma chamber, known as the upper-crustal magma reservoir, directly beneath the surface in 2013 that measures 2,500 cubic miles (10,420 cubic km).
To discover the latest chamber, Hsin-Hua Huang from the University of Utah and his colleagues tracked seismic waves from almost 5,000 earthquakes.
These readings combined data from the University of Utah Seismograph Stations, which collected shallow readings from nearby quakes in Utah, Idaho, the Teton Range and Yellowstone, and from the Earthscope array, which revealed deeper readings from temblors from more further afield.
Previous research found a relatively small magma chamber, known as the upper-crustal magma reservoir, beneath the surface
Each of these quakes created waves that echoed around the supervolcano.
The movement and structure of these waves could then be used to map the earth beneath.
The researchers said in their paper: 'The Yellowstone magmatic system from the mantle plume to the upper crust', published in the journal Science, that the reservoir contains around 98 per cent hot rock.
The remaining 2 per cent is molten rock and is too deep to directly cause an eruption, they added.
'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.
They applied their geospeedometer to four large eruptions:
'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.'
VOLCANO'S GLOBAL DEVASTATION
A volcanic eruption of a similar size to Laki eruption that hit Iceland in 1783 could have global impacts according to the new report.
Although the volcano was only rated at VEI 5 on the Volcanic Explosivity Index, it had a profound reach.
The eruption itself caused 9,350 deaths in Iceland and only caused moderate damage.
However, during the eight months that it erupted, it emitted huge amounts of sulfuric aerosols, ash and other gases.
This caused 'one of the most important climatic and socially repercussive events of the last millennium', according to the scientists at the European Science Foundation.
In Iceland an estimated 20–25% of the population died in the famine and from fluorine poisoning after the fissure eruptions ceased.
The map above shows major volcanic eruptions from the past 2,000 years and some from the last 2m years
Around 80% of sheep, 50% of cattle, and 50% of horses died because of dental and skeletal fluorosis from the 8 million tons of hydrogen fluoride that were released.
There is evidence that the Laki eruption also weakened African and Indian monsoon circulations, reducing precipitation over areas in Africa.
The resulting famine that afflicted Egypt in 1784 caused nearly one sixth of the country's population to die out.
In Britain the summer of 1783 was known as the 'sand summer' because of the ash fallout and an estimated 25,000 people died due to breathing problems.
Extreme weather hit much of Europe, North America and the Gulf of Mexico for several years in the aftermath of the eruption, says the report.
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