It is not a strange kind of moss, it is a lichen. Dog Lichen (Peltigera canina) is the result of a symbiotic relationship between a fungus and cyanobacter algae. It lives in woods, between mosses or on a rotting tree stump. This kind of lichens does not like dry weather, in summer it shrinks into something pale and grey. But in winther when it rains a lot it opens up and shows strong contrasting colours.
The blackish surface is the thallus, a mix of fungus mycelium and algae on the surface, exposed to sunlight. On this thallus grow the reddish brown apothecies that carry the fungus spores.