Yosemite National Park

[Pu241]

I'd imagine it would be like St Helens but bigger

Uh, yeah, bigger, much bigger!

St Helens was only 9 MT.

Super-volcano's probably measured in 100's of MT.
Easily, an order of magnitude, or more.
Depending upon size could also be an extinction level event for humans.
78,000 yrs ago, there is evidence of just such an event in human DNA.

[pyrothehitman]

very cool pic.. great job

[Pu241]

My bad

Super-volcano is 1,000 time more powerful than MT St Helen's
August 2009 National Geographics

http://ngm.nationalgeographic.com/2009/08/yellowstone/achenbach-text/1

9,000 MT will likely ruin your day, maybe your week!