What's the difference between a "fen" and a "dale"?

From Wikipedia regarding dale:

A dale is a valley. The word dale comes from Old English dael and is related to Old Norse dalr.

_{(source: wikimedia.org)}

And fen:

A fen is a type of wetland fed by mineral-rich surface water or groundwater.

Fens are characterised by their water chemistry, which is neutral or alkaline, with relatively high dissolved mineral levels but few other plant nutrients. They support a wide range of animals and plants, many of which are tall marsh plants growing closely together.

They are both related to geography but have different meanings and are also somewhat geographically specific.

A fen is a type of wetland. In Eastern England there is an area known as The Fens that although now largely drained typified this sort of geographical feature.

Dale means valley and is part of many place names, mostly in the North of Britain. The Yorkshire Dales is an upland region in Northern England.

A fen is wetland, but it doen't have to be particularly lower than the surrounding land. A dale is a valley, and it doesn't have to be wet.