The Forest on the Mega Volcano
I would guess about 50% of people know this, and I should not take it for granted that everyone does. But Yellowstone sits on top of a giant caldera, and it's due to go off any time (at least, geologically due!) If you look at a map of Yellowstone from above, you can see the clear outline of the caldera. When the mega-volcano strikes, it'll be a doozy!
The rest of this entry is here. There's also a review of the new Nikon 200-400mm lens and an interview at Trip Atlas! Full day!