Yellowstone super-volcano may be super sneaky
A paper in the latest issue of GSA Today indicates that when it comes to warning signs of an eruption at Yellowstone, we may be looking for the wrong things.
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“Geologist [I'm Climate Change]”
Since: Mar 07
#1 Sep 5, 2012
Like that one.
In all cases of supervolcanoes documanted worldwide so far, the volcano is the result of a pluton advancing from the base of the crust intersecting the surface.
The result of the surface intersection and breach of the pluton at or slightly above gas equilibrium with the base of the crust is... A bloody great big hole in the ground filled with densely welded ash flow tuff, and a various assemblage of outflow tuff ranging from welded ash flow tuff to Sillar (sintered bits with all the fine ash removed via catastrophic hurricane like storms at the edge of the outflow field). End result: a supervolcano if the volume of erupted product is over 1000Km3.
The aftermath is a degassed pluton which continues to buoyantly rise to about 10Km depth and generats a hydrothermal system & occasional lava domes when ingress of new magma from the base of the crust intersects the residual magma in the pluton.
Yellowsone is unique in that it is a hotspot supervolcano so that the last supervolcano caldera is now being invaded by hotspot basalt which keeps it hot enough to produce a plastic lid; (lava domes only erupted with the lid cooled to rigidity by an overlying ice cap & lake.
The current vigorous hydrothermal activity is due in fact to a small pluton which intersected the pool of residual magma near the caldera W. rim about 150000 years ago while the caldera was buried under a big ice cap The pluton intersected the residual magma (about 15000Km3) & exchanged gas charging up the system, but not enough to remake the system into an explosive volcano. About 1000Km3 of rhyolite domes erupted in 3 glacial periods (150000Bp,~100000Bp, and about 700000Bp). That pluton was similar in size or smaller than the island park caldera pluton (about 500Km3 total erupted volume).
Now the fun bit (grab the tweeters); The next advancing pluton is centred under Mt Washburn in the NE. part of the park and is still at intermediate crustal depths. The uplift associated with this pluton has raised the NE. rim (Yellowstone falls area) and has backed up Yellowsone lake behind the rim. The still liquid residual magma in the old pluton is now slowly oozing ESE. toward the park boundary raising the SE. rim as it flows away from the Mt. Washburn uplift.
This advancing pluton is about the same size as the caldera forming pluton of ~600000 years ago and is likely to miss the old residual magma as a result of squelching it sideways out of the way.
Usual Yellowstone super eruptions are usually immediately postglacial as a result of sudden decompression of the overlying cooled & brittle crust due to disappearance of the previously overlying ice cap.
Have a nice day: Ag
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