How does a pond form into a bog?

Question

(the process of ecological succession leading from a pond to a bog)

Answer 1

If a pond is terrestrialized by special plants ( especially Sphagnum species ) a bog can develop.

Here you find the complete  process of ecological succession of LAKE-FILL BOG and others incl. a lot of illustrations:

http://www.nescb.org/epublications/summe...

Answer 2

Less and less water seeps in, more and more plants grow. I think its kinda quicksand. People lose shoes in this mud like nature made swamp.