One small hamlet, Birkerthwaite (grid reference SD179982), lies in a shallow valley near the centre of the fell, but other than this the only human habitations are scattered hill farms.
Between these points are a plethora of smaller crags and knolls, separated by shallow valleys and bogs, giving the high fell an uneven and chaotic appearance.
The BVG are thought to have formed in the early Ordovician by island arc volcanic activity, due to subduction during the closing of the Iapetus Ocean.
The south and south-eastern portion of the fell is composed of a sequence of tuff beds with highly variable composition: from rhyolitic through to basaltic.
In the north-western corner of Birker Fell, extensive faulting has juxtaposed the BVG rocks against granites of the late Ordovician Eskdale Intrusion.