Enormous volcanic eruptions more than 100 times the size of ordinary volcanic eruptions like Mount St. Helens. with potential to end civilizations may have surprisingly short fuses, researchers have discovered. These eruptions are known as super-eruptions because they are They spew out tremendous flows of super-heated gas, ash and rock capable of blanketing entire continents and inject enough particulate into the stratosphere to throw the global climate into decade-long volcanic winters.
There is evidence that one super-eruption, which took place in Indonesia 74,000 years ago, may have come remarkably close to wiping out the entire human species.
"Our study suggests that when these exceptionally large magma pools form they are ephemeral and cannot exist very long without erupting," said Guilherme Gualda, the assistant professor of earth and environmental sciences at Vanderbilt University who directed the study.
The study was performed on the remnants of the Bishop Tuff, the Long Valley super-eruption that occurred in east-central California 760,000 years ago. Using the latest methods for dating the process of magma formation, Gualda and his colleagues found several independent lines of evidence that indicate the magma pool formed within a few thousand years, perhaps within a few hundred years, before it erupted, covering half of the North American continent with smoldering ash.
These giant magma pools tend to be shaped like pancakes and are 10 to 25 miles in diameter and one half to three miles deep. In the beginning, the molten rock in these pools is largely free from crystals and bubbles. After they form, however, crystals and bubbles form gradually and progressively change the magma's physical and chemical properties, a process that halts when an eruption takes place.
As far as geologists can tell, no such giant crystal-poor magma body currently exists that is capable of producing a super-eruption. The research team believes this may be because these magma bodies exist for a relatively short time rather than persisting for hundreds of thousands of years as previously thought.
According to Gualda, the estimates for the 100,000 year-plus lifetimes of these giant magma bodies appears to be an artifact of the method that geologists have used to make them. The measurements have been made using zircon crystals. Zircons are commonplace in volcanic rocks and they contain small amounts of radioactive uranium and thorium, which decay into lead at a set rate, allowing scientists to accurately determine when the crystals formed. They are extremely useful for many purposes because they can survive most geologic processes.
However, the fact that zircons can withstand the heat and the forces found in a magma chamber means that they are not good at recording the lifetimes of crystal-poor magma bodies.Gualda and his colleagues took a different approach in his studies of the Bishop Tuff. They determined crystallization rates of quartz – the most abundant mineral in the deposits – to gather information about the lifespan of these giant magma bodies.
They developed four independent lines of evidence that agreed that the formation process took less than 10,000 years and most likely between 500 to 3,000 years before the eruption. They suggest that the zircon crystal measurements record the extensive changes that take place in the crust required before the giant magma bodies can begin forming as opposed to the formation itself.
"The fact that the process of magma body formation occurs in historical time, instead of geological time, completely changes the nature of the problem," said Gualda. Instead of concluding that there is virtually no risk of another super-eruption for the foreseeable future because there are no suitable magma bodies, geologists need to regularly monitor areas where super-eruptions are likely, such as Yellowstone, to provide advanced warning if such a magma body begins to form.
According to a 2005 report by the Geological Society of London, "Even science fiction cannot produce a credible mechanism for averting a super-eruption. We can, however, work to better understand the mechanisms involved in super-eruptions, with the goal of being able to predict them ahead of time and provide a warning for society. Preparedness is the key to mitigation of the disastrous effects of a super-eruption."
The Yellowstone National Park caldera, which covers a 25- by 37-mile (40- by 60-kilometer) swath of Wyoming, is an ancient crater formed after the last big blast, some 640,000 years ago. The simmering volcano has produced major eruptions—each a thousand times more powerful than Mount St. Helens's 1980 eruption—three times in the past 2.1 million years. The supervolcano has recently caused miles of ground to rise dramatically, scientists report beginning in 2004, which saw the ground above the caldera rise upward at rates as high as 2.8 inches (7 centimeters) a year. Is it poised for yet a fourth major explosion?
Some 600,000 years ago there was a colossal cauldron of magma, a supervolcano, that exploded with such violence that it left an ash layer almost ten feet deep a thousand miles away in eastern Nebraska killing all plant life and covering almost all of the United States west of the Mississippi. Modern geological surveys have shown that this supervolcano erupts catastrophically every 600,000 years, and the land that supervolcano is trapped in was called by Blackfoot Indians 'the land of evil spirits' -what we call today, Yellowstone National Park.
A report from scientists at the University of Utah showed that the “supervolcano” underneath Yellowstone has risen at a record rate since mid 2004. Apparently, a “pancake-shaped blob” of molten rock the size of Los Angeles was pressed in to the slumbering volcano, some six miles down.
“There is no evidence of an imminent volcanic eruption or hydrothermal explosion. That’s the bottom line,” says seismologist Robert B. Smith, lead author of the study and professor of geophysics at the University of Utah. “A lot of calderas [giant volcanic craters] worldwide go up and down over decades without erupting.”
The Daily Galaxy via Vanderbilt University and PLoS ONE