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A slot canyon is a narrow canyon, formed by the wear of water rushing through rock. A slot canyon is significantly deeper than it is wide. Some slot canyons can measure less than 1 metre (3 ft 3 in) across at the top but drop more than 30 metres (98 ft) to the floor of the canyon.
Most slot canyons are formed in sandstone and limestone rock, although slot canyons in other rock types such as granite and basalt are possible. Even in sandstone and limestone, only a very small number of creeks will form slot canyons. This is due to a combination of the particular characteristics of the rock, and regional rainfall.
Slot canyons around the world 
Slot canyons are found in many parts of the world, predominantly in areas with low rainfall. Some of the most well known slot canyons are to be found in the Southwestern United States. Other significant areas include the Sierra de Guara in northern Spain, the Pyrenees on the border of France and Spain, and the Blue Mountains in New South Wales, Australia.
The largest known area of slot canyons in Australia is in the Blue Mountains, west of Sydney. They occur in a narrow band of sandstone that runs roughly 30 kilometres (19 mi) from east to west, and about 100 kilometres (62 mi) from south to north. The majority of these canyons are in the Wollemi Wilderness, and are difficult to access. A small number are regularly visited by canyoners on weekends in summer. The Grand Canyon, near Blackheath, has a tourist track along its rim, but requires abseiling (rappelling) or swimming to visit fully.
Sandstone slot canyons can also be found in a few more remote parts of Australia, including:
- the Bungle Bungles in Purnululu National Park, Western Australia
- Karijini National Park in Western Australia
- Carnarvon Gorge in Queensland
United States 
The U.S. state of Utah has the largest concentration of slot canyons in the world. Utah slot canyons are found places such as Zion National Park, Bryce Canyon National Park, and Grand Staircase-Escalante National Monument. Slot canyons of Utah include Buckskin Gulch, the longest slot canyon in the world, and The Narrows (Zion National Park). Northern Arizona also has a high concentration of slot canyons including Antelope Canyon and Secret Canyon, two of the most famous slot canyons located near Page, on the Navajo Nation. There are also numerous slot canyons in the valley between US Route 89 and the Vermilion Cliffs in Arizona, and can be seen as one descends into the valley on US 89, but these are also on the Navajo reservation and are closed to the public. Several canyons accessible to the public are within Zion National Park and Death Valley National Park.
Drowning danger 
Local as well as distant storms can cause dangerous flash flooding in slot canyons, and expert guides advise avoiding hiking in them if there is any sign of rain. In many slot canyons, it can be miles before a safe exit or rescue is possible.
On August 12, 1997, eleven tourists, including seven from France, one from the United Kingdom, one from Sweden and two from the United States, were killed in Lower Antelope Canyon 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, seven miles upstream. The lone survivor of the flood was tour guide Francisco "Poncho" Quintana, who had prior swift-water training. At the time, the ladder system consisted of amateur-built wood ladders that were swept away by the flash flood. Today, ladder systems have been bolted in place, and deployable cargo nets are installed at the top of the canyon. At the fee booth, a NOAA Weather Radio from the National Weather Service and an alarm horn are stationed.
In September 2008 a couple drowned in Utah, and in 2005 a group of students in a nearby location also drowned, despite wearing wetsuits.