What is a canyon?
A canyon is a landform that is deep, narrow and steep-sided. Its walls often show bands of rock, and a river or stream usually runs along the bottom. The Coloured Canyon in Sinai has walls striped with different colours. Far away in Oman, Wadi Nakhr is another canyon. A canyon forms when running water erodes rock for a very long time, even millions of years. A valley is also a low place cut by a river or ice, but its sides are gentle and wide. To work out how a landform formed, scientists look at clues. A small gully with plants along it and gently worn sides was probably made by a stream. If the gully is deeper after heavy rain, we can predict that heavy rain running over bare, sloping ground will cut more gullies. Understanding how landforms form helps people choose safe places to build and farm.
| Feature | Canyon | Valley |
|---|---|---|
| walls | tall and steep | gently sloping |
| width | narrow | wide with flat ground |
| layers of rock | often easy to see in the walls | hidden under soil and plants |
| river | usually at the bottom | often along the middle |
| If … | then … |
|---|---|
| heavy rain runs through the gully | the gully gets deeper |
| rain runs down a bare slope | it may cut a new gully |
Landform cards. Make four cards: canyon, valley, mountain, dunes. On each card draw a simple side view and write two words that describe it (for example steep, wide, high, sandy). Mix the cards and let a friend describe one to you without naming it, so you can guess. Then write three questions you wonder about canyons, starting with Why, How and What.