A canyon (or gorge) is a big crack in the ground, or a very deep valley. Most canyons are made by rivers. A few are made by earthquakes. They can be big, like the Grand Canyon, or small.
Canyons can be formed by erosion by running water which will take rocks and soil away.
Canyons are formed by the incision of a river in a plain, which digs itself into the plateau in a long erosion process. Prominent cliffs are formed because layers of harder rock are more resistant to hanging erosion (denudation) and are exposed, whereas underlying morphologically softer layers are cleared out more. The difference in hardness ultimately creates stepped slopes. Canyons are more common in dry areas because weathering has a lesser effect there than in wetter areas, so the surrounding uplands are preserved and the canyon walls are not flattened. Canyons often form from resistant sandstone, limestone, or granite. Particularly narrow canyons are called slot canyons, which roughly corresponds to the German term Klamm, an example being Antelope Canyon in northern Arizona.
There are also submarine canyons, typically at river mouths as a submarine extension of the river course.
Some valleys called canyon or cañon in the local language do not meet this geological definition, for example Bryce Canyon.
Conversely, many geological cañons do not have canyon or cañón in their name, but different words for gorge in the various national languages. Even in the USA many are called "gorges" or "ravines".
