following (abbreviated) definitions come from the Glossary of Geology published by the American Geological Institute. I have also included the definition of a ravine. They are listed in order of increasing sizeᆞ Gully: A very small valley, such as a small ravine in a cliff face, or a long, narrow hollow or channel worn in earth or unconsolidated materials (as on a hillside) by running water and through which water runs only after a rain or the melting of ice or snow; it is smaller than a gulch. Gulch: A term used in the western US for a narrow, deep ravine with steep sides, larger than a gully. Ravine: A small narrow deep depression, smaller than a gorge or canyon but larger than a gully, usually carved by running water; esp. the narrow excavated channel of a mountain stream. Gorge: A narrow, deep valley with nearly vertical rocky walls, enclosed by mountains, smaller than a canyon, and more steep-sided than a ravine. Canyon: A long, deep, relatively narrow steep-sided valley confined between lofty and precipitous walls in a plateau or mountainous area, often with a stream at the bottom; similar to, but larger than a gorge. One can imagine the Grand Canyon as a really big feature, yet I wonder what a Grand Gully would like (there is a Grand Gully in New Zealand)

following (abbreviated) definitions come from the Glossary of Geology published by the American Geological Institute. I have also included the definition of a ravine. They are listed in order of increasing sizeᆞ
Gully: A very small valley, such as a small ravine in a cliff face, or a long, narrow hollow or channel worn in earth or unconsolidated materials (as on a hillside) by running water and through which water runs only after a rain or the melting of ice or snow; it is smaller than a gulch.

Gulch: A term used in the western US for a narrow, deep ravine with steep sides, larger than a gully.

Ravine: A small narrow deep depression, smaller than a gorge or canyon but larger than a gully, usually carved by running water; esp. the narrow excavated channel of a mountain stream.

Gorge: A narrow, deep valley with nearly vertical rocky walls, enclosed by mountains, smaller than a canyon, and more steep-sided than a ravine.

Canyon: A long, deep, relatively narrow steep-sided valley confined between lofty and precipitous walls in a plateau or mountainous area, often with a stream at the bottom; similar to, but larger than a gorge.

One can imagine the Grand Canyon as a really big feature, yet I wonder what a Grand Gully would like (there is a Grand Gully in New Zealand)