Erris, in common with most of inland Ireland, became covered in extensive native woodland a few thousand years after the last Ice Age retreated (approx 15,000 years ago) but its northern and western shores remained relatively lightly afforested. Across inland Erris, the remains of these forests can be seen across the blanket bog landscape in the form of fossilised greying tree stumps which are mainly the remains of ancient Scots pine trees. These become most obvious where there has been harvesting of turf (peat) for fuel. The odd petrified bog oak can be found too.