This picture is from the Laugavegur trail in Iceland. The mountain pictured is Stóra Súla (E. Big Column), on the section between the Hvanngil and Emstrur huts. The hyper green moss along the river banks is typical for Iceland. We call it dýjamosi (E. bog moss). It will often cover considerable areas and although it may look stable it can typically swallow an unexperienced hiker up to his waist. This is a much more entertaining experience for his companions than himself.
Here is another picture of dýjamosi on a black sand in south Iceland. Also check out other great pictures of Iceland by Alex Nail.