Weather in Iceland is wet and therefore suitable for moss which are not vascular plants and hence have no system to transport water through the plant. They also require sunlight for photosynthesis which is well available to them again as there are almost no trees growing in Iceland. Moss is a common plant in Iceland that helps to give softness to rugged lava fields.
Aa lava covered with moss.
Pictures taken on Snæfellsnes Peninsula in Western Iceland.
Moss carpet is soft but somewhat hazardous to walk on because it hides surface irregularities below.
Close-up of moss cover.
And even more closer view.