Sandstone is most susceptible to this kind of earth carving, but slot canyons can also form out of limestone, granite, basalt and other types of rock. The water seeps into the crack, bringing with it rocks, sediment, and other debris that carve a little bit away from the inside edges of the crack. It happens like this: the initial crack is covered by a flash flood from heavy rain pooling in a natural wash. and Australia, where the perfect canyon-forming combination of soft rock and extreme climate collide. Slot canyons-the narrow, tall channels through otherwise solid rock-can be found anywhere in the world, but are particularly numerous in the southwestern U.S.
But add a few million years and that crack opens into a deep winding gorge in the earth, with a narrow path and sheer sides. It begins with a simple crack in the rock on the ground.
