Posted on 12/23/2006 3:54:50 PM PST by blam
Eruption May Have Been Bigger
Larry O'Hanlon, Discovery News
Dec. 21, 2006 — One of the largest volcanic eruptions on record just got bigger.
The Taupo Volcanic Zone of New Zealand appears to have had twin eruptions only 20 miles apart within days of each other a quarter-million years ago. Each eruption belched out more than 25 cubic miles (100 cubic kilometers) of rock and volcanic ash.
This is the first evidence of twin supervolcanic eruptions.
"It's possible one of these triggered the other," said geologist Darren Gravley of the University of Auckland, New Zealand. But exactly how the triggering might have worked is uncertain.
What is clear from the explorations of Gravley and his colleagues of the Mamaku and Ohakuri volcanic deposits is that they were created very close in time. That's surprising, since most caldera or "supervolcano" eruptions in any one region tend to be tens of thousands of years apart, or at least that's been the general idea until now.
Among the signs that the rocks from the two eruptions were piled on one another is the conspicuous lack of erosion on the first volcanic deposits — which is striking, considering the rainy climate.
Previous studies that looked only at the radioisotope dates of the volcanic rocks from the eruptions missed the timing details, Gravley said, because they have a margin of error of 10,000 years — way too low a resolution.
"You’ve got to look at the physical evidence," said Gravley. "It's really getting into the nitty-gritty. From the stratigraphy (rock layers) it’s clear two were erupting at the same time. That just blows away any (regional frequency) studies out of the water."
Gravely and his colleagues have published their double eruption discovery in the latest issue of the Bulletin of the Geological Society of America.
The bad news is that double eruption represents a whole new way that supervolcanoes can threaten humanity.
"This is of course a major issue to consider for volcanic risk," said caldera researcher Gerardo Aguirre-Díaz of the Universidad Nacional Autónoma de Mexico in Juriquilla, Mexico.
Caldera eruptions are far less frequent than other volcanoes, but when they do erupt, "the consequences for the surroundings and in general for the world would be enormous, because these explosive eruptions are many orders of magnitude bigger than a more common eruption from a volcano, such as Mount St. Helens or Vesuvius."
The term "overdue" is horrifically mis-used in many cases, and in any event, it's not true of Yellowstone.
From the Yellowstone Volcano Observatory website:
Is it true that the next caldera-forming eruption of Yellowstone is overdue?
No. First of all, one cannot present recurrence intervals based on only two values. It would be statistically meaningless. But for those who insist... let's do the arithmetic. The three eruptions occurred 2.1 million, 1.3 million and 0.64 million years ago. The two intervals are thus 0.8 and 0.66 million years, averaging to a 0.73 million-year interval. Again, the last eruption was 0.64 million years ago, implying that we are still about 90,000 years away from the time when we might consider calling Yellowstone overdue for another caldera-forming eruption. Nevertheless, we cannot discount the possibility of another such eruption occurring some time in the future, given Yellowstone's volcanic history and the continued presence of magma beneath the Yellowstone caldera.
I can see that. You left out the 'looming' Bird Flu Pandemic.
They didn't have a mere supervolcano. They had to have a double-supervolcano! nyah!
America's Explosive Park
By Larry O'Hanlon
http://dsc.discovery.com/convergence/supervolcano/under/under.html
Yellowstone National Park sits atop a subterranean chamber of molten rock and gasses so vast that the region, known for its geysers and grizzlies, is arguably one of the largest active volcanoes in the world.
Granted, it's not your typical volcano, either in scale (it's huge), appearance (it's a vast depression, not a single mountain) or frequency of eruption (at least hundreds of thousands of years apart).
But it is active, and the evidence is everywhere.
A relatively close-to-the-surface magma chamber — as close as 5 miles underground in some spots — fuels thousands of spewing geysers, hissing steam vents, gurgling mud pots and steaming hot springs that help make Yellowstone such an otherworldly and popular tourist attraction, with 3 million summer visitors.
Molten rock and gas in a chamber near the Earth's surface is similarly present below "traditional" cone-shaped active volcanoes, like Mount St. Helens in Washington state.
But there are differences. Huge differences.
The crater atop Mount St. Helens is about 2 square miles. The Yellowstone "caldera" — a depression in the Earth equivalent to a crater top — is some 1,500 square miles.
(snip)
I know, the movie was crap. But cheesy disaster movies are great for a laugh.
How dare you dash people's paranoia!
You're just a fun-hater.
No. Rush to an equatorial region, otherwise you'll freeze or starve to death.
BUT! If it does explode, would you recommend hiding in the closet or under the bed?The question should be more along the lines of 'the smoker or the fireplace' (both UNLIT of course) ...
"Then it's their problem."
Nah. If it goes off in China, you're still going to die.
Yeah, but still quite a bit smaller.
The largest known explosive eruption was the La Garita Caldera in Colorado 28 million years ago - about 5,000 cubic kilometers of material.
Toba is second with 2,800 cubic km.
The largest of the Yellowstone eruptions (the one three eruptions ago, 2 million years ago) is 4th with 2,500 cu km.
The last Yellowstone eruption 640,000 years ago was about 1000 cubic km of stuff - the largest Taupo eruption was 500 cubic km.
Taupo seems to erupt a lot more often than Yellowstone though.
WE'RE ALL GONNA DIE!!!
Anyone want a beer?
:)
Oh I just think people should be paranoid about the right things - people aren't paranoid ENOUGH, for example, about really big earthquakes in places like Utah, Nevada, etc, but they're way too paranoid about Yellowstone, and La Palma in the Canaries collapsing and causing a tsunami, etc.
Go get a lawn chair, pop a brewski and sit out in the back yard and watch the fireworks.
Is the sky falling again?
No. It already fell, we survived.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.