From Bushwalk Australia
An extensive depression in the surface of the land, sometimes surrounded by mountains. A valley often contains a river or other watercourse and there are a variety of different types. These were formed in different ways. For example:
- River valley (usually V shaped and caused by erosion of flowing water)
- Glacial valley (formed by glacial erosion)
- Hanging valley (a secondary valley that sits at a higher level than the valley it connects with)
- Rift valley (caused by expansion of the Earth's crust due to subterranean tectonic activity).