There's a great many weird things to choose from, but I'll tell you what warps my mind: seeing things we normally think of as temporary preserved forever in stone.
|Ripples in the Moenkopi Formation|
I'm sorry, but that's just bloody weird.
Walk around Wupatki, and you'll see ancient ripples exposed.
|Ripples, Moenkopi Formation, Wupatki National Monument|
And it gets weirder.
|Mudcracks, unidentified sedimentary rocks, Richmond Beach, WA|
So imagine my surprise when I learned that sometimes, if the mud cracks get covered by a nice layer of sand or silt, they can sometimes last forever.
|Mud cracks, unidentified sedimentary rocks, Richmond Beach, WA|
Mud cracks are a dead giveaway that the place these sedimentary rocks formed in suffered from wet and dry cycles. (I wish these told us more, but they're in boulders ripped out of their context, so I haven't got the slightest bloody clue what formation they're from. But if you ever make it down to Richmond Beach in Seattle, wander a bit down the beach toward the spot where the train tracks bend, and have yourself a look at the severely out-of-place mauve rocks shoring up the railway bed.)
And it gets weirder. And wormier.
|Burrow casts, Moenkopi Formation, Meteor Crater|
But that's not the mind-warping, worldview-changing, weirdest bloody thing I've ever seen. This is:
|Raindrops preserved in sediments, Almeria, Spain|
Raindrops. Fossil fucking raindrops. Can you think of anything more unlikely to survive millions of years and who knows what vagaries of erosion than a raindrop? Such a delicate thing, such a tiny thing, a memory of a brief shower, so long ago, living to tell the tale.
Geology, my friends, is weird, and wonderful.