Sunday, September 30, 2012

Yellowstone Caldera Posses Little Risk

The Yellowstone Caldera has erupted as a super-volcano in the past. However, the Eruptions Blog at Wired Magazine explains that it is unlikely to do so in the foreseeable future:
Just because Yellowstone has produced three very large eruptions over the last 2.2 million years doesn’t mean that you should expect such an eruption. The caldera system has had plenty of smaller, dome-forming or explosive eruptions in the intervening years (and since the last caldera-forming eruption; see above), so in terms of the likeliest events, that is what to expect. In the paper by Guillarme Girard and John Stix in GSA Today, they suggest that the likeliest events to happen at Yellowstone in the near future are small, dome-forming eruptions or phreato-magmatic (water-influenced) explosions that follow pre-existing faults in the caldera, especially along the western rim. In fact, another study by Christensen and others (2007) showed that probabilistically, another caldera-forming eruption is the least likely scenario for future activity at Yellowstone. 
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As for the future, it depends on what part of the caldera you are examining. Girard and Stix (2012) identify three zones at Yellowstone (see right) that could produce different potential eruptions: (1) fault-associated zones where voluminous rhyolite eruptions could occur – this is the most likely location for renewed activity; (2) a zone between Norris Geyser Basin and Mammoth where phreatic or phreatomagmatic (water-driven) eruptions could occur and (3) a small fault zone on the east side of the caldera were basaltic eruptions could occur. All of these potential eruptive types present hazards to the general public, varying from significant ash fall and pyroclastic flows that could reach the neighboring area to localized hydrothermal explosions. However, none of these are the “endtimes” scenarios that jump to everyone’s mind the minute Yellowstone has another one of its many earthquake swarms or caldera floor inflation events.

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