Geology
The primary rock types in the summit area are the plagioclase-phyric andesite lavas of the Birker Fell Formation. Bands of volcaniclastic sandstone and andesite sills are also present. Rhyolite and lapilli-tuff appear amongst the northern crags, with outcrops of the Craghouse Member on the north west ridge.
Read more about this topic: Pillar (Lake District)