Sundewd, this is a very simple description of a very complex subject:
A bog is an area of wet, soggy ground, usually with a slow moving inflow
and outflow of water, and it's formation is continuous, with new generations
of Sphagnum moss and other acid tolerant plant species that grow up over the
remains of earlier generations, creating layers of peat. Bogs generally form in
depressions in the terrain leaving them at or near the water table, so the surface
is always wet and usually covered with mosses and low-growing plant life.
Lacking nutrients, decomposition of plant debris is slow, resulting in a low PH
factor and the mineral content is virtually nil due to seepage and by flooding from
rains. Bogs also form from old lakes that have slowly been filled in with debris and
silt until there is more land than water. A few variations are Sedges, Fens,
Poccosins, Savannahs and others that I can't remember right now.
Hope this helps, but it is only the "tip of the iceberg" as they say.
Dyflam, those are great pictures. Hope mine look like that this Spring!