Antelope Canyon is one of those places where the postcard light beam shot hides the actual rock story underneath it. What you're standing inside is Navajo Sandstone, laid down in the Early Jurassic something like 190 to 200 million years ago, and it did not start as a canyon at all. It started as a massive erg, a Sahara scale field of migrating dunes near the equator on old Pangaea. That aeolian origin is why you get the crossbedding everywhere on the walls, those sweeping diagonal lines cutting across each other instead of sitting flat like a lake bed. Each set of lines is a fossilized dune slope, the lee face of a wind blown mound of sand recorded in stone before the next dune migrated over it and started a new set. Flat horizontal bedding means quiet water. Big crossed diagonal bedding at that scale basically only happens from wind stacking dry sand into dunes, so every wall in that canyon is a snapshot of ancient wind direction. Fast forward past all the burial and lithification to why the canyon looks the way it does. Antelope Canyon isn't cut by a steady river like the Grand Canyon. It's carved almost entirely by flash floods, short violent pulses of water that can come from a storm many miles upstream with zero rain falling at the slot itself. That water enters a narrow joint in the sandstone already loaded with sand and grit, and moving fast through a tight channel it behaves less like a river and more like a pressure washer. Navajo Sandstone is porous and only lightly cemented, mostly rounded quartz grains without much glue holding them together, so instead of the water widening the crack into a broad valley the way it would in tougher rock, the sand slurry scours and polishes in swirling turbulent patterns. That's the mechanical reason for the flowing, almost liquid looking curves on the walls. It's not artistic erosion, it's sandblasting inside a pipe that keeps changing shape as it gets sandblasted. The color is a separate story from the shape. That orange to red gradient everyone chases with a camera comes from iron oxide, hematite mostly, staining the quartz grains and cement unevenly through the rock. Where iron rich fluids moved through the porous sandstone over geologic time you get the deep red and orange bands, where iron was leached out or never concentrated you get paler cream and white zones. Combine that blotchy staining with light bouncing off the smoothed curved walls and you get the layered glow people associate with the place, but it has nothing to do with how the canyon was shaped. Purely a mineral chemistry overlay on top of the erosion story. Link in 🧵