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View Full Version : Supervolcanoes may evolve more quickly than thought



Swift
2012-Jul-18, 04:47 PM
From Science News (http://www.sciencenews.org/view/generic/id/341084/title/Supervolcanoes_evolve_superquickly)

The biggest eruptions on Earth may happen faster than volcanologists had thought. Giant blobs of magma appear underground and then pour onto the surface within centuries, suggests a new study of a California supereruption.

If the work holds true for other volcanoes, it means the most powerful eruptions don’t have magma chambers beneath them for very long. So if big changes start happening, like the ground rising or new geysers spouting, volcanologists might expect an eruption sooner rather than later. Yellowstone, for one, experienced a supereruption about 2.1 million years ago.

“The fact that at Yellowstone there’s no giant magma body right now doesn’t mean that in hundreds to thousands of years we couldn’t have one,” says Guilherme Gualda, a geologist at Vanderbilt University in Nashville. “By understanding these time scales better, we know better what to expect.”

Gualda and his colleagues report the discovery May 30 in PLoS ONE.


Also reported by the BBC (http://www.bbc.co.uk/news/science-environment-18269593)

NEOWatcher
2012-Jul-18, 06:10 PM
Where do they draw the line for "supereruption" and "giant" magma chamber?
Per wiki (http://en.wikipedia.org/wiki/Yellowstone_National_Park), there were 2 other "cataclysmic" eruptions since then.
There's also a rather large magma chamber there too.

dgavin
2012-Jul-18, 07:48 PM
What Neo said, some of the information in that article, doesn;t match the know science. Such as the following 3-d represntation of Yellowstons Magma Chamber from Univeristy of Utah, hosted at Ureka Alert. http://www.eurekalert.org/multimedia/pub/5718.php (http://www.eurekalert.org/multimedia/pub/5718.php)

That being said, that image represent's what can be determined from siesmic tomology. In truth, it's known that the magma at Yellowstone gets as close as 1.2 miles depth from surface in some areas. So it doesn't actualy have a lot of crust to punch through, compared to most other volcanic regions where it more like 2.5-8 miles of crust overlaying the magma chambers.

So A 100 year build up for a supereruption is not as short as they are making it sound, actully. The telling sign would be if the cycles of uplift and subsidence, stop subsiding. Just basing on the amount of uplift that does historically occur during the uplift phases, A continual injection of Magma for around 15 years, would lead to a St. Helens like event. If magma contuniues to Inject for another 5 years past that, then multiple St Helens event(s) at the same could start up. 20 years past that point, you would have a VEI 7 (newberry caldera) sized mega-plinian eruption. If Magama still continues to inject past that eruption phase, maybe another 15 years, you would likely have enough magma for a dreaded VEI 8 Super-eruption. So just based on the 3 inches a year historical uplift, in 65 years you would have enough magma for some major eruptions.

That does not mean a supereurption would actually happen, 2 VEI 6 eruptions, or a larger 7.5 VEI could eliminate enough presure to prevent a major eruption.