Light filters from above onto eroded sandstone walls of Lower Antelope Canyon, a slot canyon in Arizona, USA. These smooth, angular surfaces of rock have been eroded by seasonal flash floods after thunderstorms. The water follows cracks in the sandstone of the area. The abrasive quality of the water comes from particles of sand it carries. Localised turbulence and eddy patterns in the flow of water cut natural arches, curves and holes into the rock.