The same influence of altered rocks on the topography is well seen in the valley of Great Langdale and its bordering fells hotels in the lake district .Here the Borrowdale Volcanic beds consist of alternating beds of tuffs and lava flows. Where the former have been hardened by heat they tend to stand out as precipitous crags forming minor breaks on the valley side or more spectacular scarps like those along the southern face of the Langdale Pikes.
In contrast the lava beds both above and below the altered tuffs are associated with more gentle slopes. Many of the hard rocks are easily shattered and it was on the scree slopes below Langdale Pikes that Neolithic man found that he could shape the rock fragments in much the same way as flints from the chalk. His axe 'factory' flourished and its products distributed far and wide.
Great Langdale is unique among the Lakeland valleys in that it has a distinc¬tive twisting form rather than that of a straight trough like Borrowdale or Enner¬dale . At its upper end in Mickleden, the valley is running south¬east until it is joined by Oxen dale near Stool End Farm. From this point the direction of the valley changes to run east northeast for about a mile before it resumes its original southeast alignment once again as far as Skelwith Bridge . In its segmented plan Great Langdale exhibits the effects of structural control, viz. folding and faulting of the rock beds.
The Borrowdale Volcanic Series have been folded into a broad elongated dome whose main axis is west¬southwest to eastsoutheast. Both Oxendale and the main section of the Lang¬dale Valley between Stool End and the New Dungeon Ghyll Hotel result from erosion along the anticlinal axis. * In contrast, the other segments of the valley like Mickleden and that downstream from Chapel Stile have been excavated along a zone of shattered rock coinciding with a series of joint planes.
Even away from the main valley floor on the low col which leads over to Blea Tarn , the weaker rock has given rise to a distinct topographic feature. On the hillside above the Bleatarn House there is a narrow wooded gully running diagonally across the main slope which coincides with the same zone of weakened rocks. Much of the country hereabouts and in the Great Lang¬dale valley has been fashioned by ice , but in areas such as this there is no doubt that its erosional tendency has been greatly helped by the preexisting structural control.
Not all the scenery associated with the volcanic rocks is as spectacular as that found around Scafell or the head of Great Langdale with the long ridge of Bow¬fell. Around Ambleside and Grasmere, the countryside is both lower and tamer, and with wider valleys there is not quite the same enclosed atmosphere. It is true that individual beds still give rise to impressive buttresses like that of Nab Scar which towers over Rydal Water. On top the fells have a very broken appearance of humps and hollows forming what is usually termed mammilated* topography.
Bare rock outcrops have been shorn by ice passing over them and in between are damp boggy hollows often with small tarns fringed with reeds and cotton grass. This mammilated topography is characteristic of the thousand foot plateau of Loughrigg Fell and many of the broad ridge tops like that running down from Heron Pike towards Rydal Water. Much farther west, in the aptly described area of the Haystacks , this broken topography with its alternation of rocky knolls and scooped out hollows is . developed to perfection . Many of the upland tarns here are quite large and because of their depth have escaped infilling. Elsewhere the hollows have become morasses of sodden peat.