Navajo Upper Antelope Canyon is a slot canyon in the American Southwest, on Navajo land east of Lechee, Arizona. Antelope Canyon was formed by the erosion of Navajo Sandstone due to flash flooding and 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, deepening the corridors and smoothing hard edges to form characteristic "flowing" shapes.