[Billyv]

Well, is this one later than Mt St Helen? I don’t recall 75% of the US becoming uninhabitable. What’s the diff?

[blam]

"Well, is this one later than Mt St Helen? I don’t recall 75% of the US becoming uninhabitable. What’s the diff?"

Size. Yellowstone is a Super Volcano.

[PIF]

Well, is this one later than Mt St Helen? I don’t recall 75% of the US becoming uninhabitable. What’s the diff?

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Mt St Helens was a 5.0 on the Volcano Explosivity Index (VEI); Yellowstone would have a 10 or greater VEI. Each number is 10X the previous, so a 10 would be 50 times bigger than a 5.0, or technically: the scale is logarithmic, with each interval on the scale representing a tenfold increase in observed ejecta criteria. One is a local phenomenon, the other is close to an ELE (Extinction Level Event), at least as current human civilization goes. One eruption lasts a few days at most, the other could last for months or longer.

The real killer is the amount of material ejected, its type and the duration of the eruption. Yellowstone would put so much ash (powdered stone by the cubic mile) into the air that much of the northern hemisphere would not have full day light for years and lower the temperature by 10s of degrees for over a 100 years. This is not to mention the effects of the mega-million tons of sulfur dioxide and other noxious gasses.

See the diff, yet?

Mount Pinatubo, Philippines in 1991 was a 6.0 VEI and the largest known in the 20th century; as was Krakatoa 1883. Mount Tambora, Indonesia in 1815 was a 7.0.

The only know super volcano eruption was Mt Toba 75,000 years ago and is credited with wiping out most of the human race.

[Paleo Pete]

PIF did a good job of explaining it already, let’s maybe look at it from a bit different perspective...

If Mt St Helens was a 2 year old with hiccups, the Yellowstone caldera will be a 3 day Metallica concert.

I won’t worry too much about it until I see reports of all the animals leaving the area in a big hurry. Deer, elk, buffalo, squirrels etc all seem to have a 6th sense and will try to escape when it happens. If we pay attention well see all sorts of birds and animals on the move and in a hurry. Then it’s time to be very worried. Their instincts work a lot better than ours do...