Any budding geologists out there should be interested, as should just about anyone who likes good visuals. This one is fabulous. It's at the Astronomy Picture Of The Day, but it's really more about geology than astronomy. Take a look. Definitely wallpaper material there. The caption is here.
I'd bring the picture over and post a small version here, but this one's copyrighted by a photographer. Besides, trust me, this one's aw-worthy.