Antelope Canyon was formed by erosion of Navajo Sandstone, primarily due to flash flooding and secondarily due to other sub-aerial processes. Rainwater, especially during monsoon season, runs into the extensive basin above the slot canyon sections, picking up speed and sand as it rushes into the narrow passageways. Over time the passageways eroded away, making the corridors deeper and smoothing hard edges in such a way as to form characteristic 'flowing' shapes in the rock.