Nancy and I recently visited one of the many slot canyons found in Utah. How do these deep, narrow canyons form?
When you are looking at stream erosion, a big clue is the direction of erosion. Fast moving water usually erodes downwards while slower moving water erodes the sides of the stream. Slot canyons form in areas that have soft rocks and periodically have flash floods. The fast moving water erodes downwards through the sandstone to form the slot canyon.
This canyon is still getting deeper, but even with the flash floods, it is still a slow process. This canyon has steps in its side that were carved by Native Americans long before Europeans came to North America. Because of the climate and abundance of sandstone, Utah has one of the highest concentrations of slot canyons in the world.