Tsé bighánílíní, 'the place where water runs through rocks' is a slot canyon protected by the Navajo Tribe. The canyons are formed erosion of sandstone, primarily 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, making the corridors deeper and smoothing hard edges in such a way as to form characteristic "flowing" shapes in the rock. On August 12, 1997, eleven adventurers were killed by a flash flood. Very little rain fell at the site that day, but an earlier thunderstorm had dumped a large amount of water into the canyon basin, 7 miles upstream.