North of Sadgill, the valley of Longsleddale narrows considerably with walls of crag on either side, the most prominent feature on the eastern side being Buckbarrow Crag. Above this and set back out of sight from the valley is a second tier of rock, Tarn Crag. Being near to the summit, this has given its name to the fell as a whole. Tarn Crag is generally held to mark the transition from Lakeland to Pennine country. Away from the fierce western flank, the fell falls in long easy slopes of coarse grass and heather, with little outcropped rock in evidence.