GEOLOGY 
as the Outer Pennine Fault, which extends past the western foot of Cross 
Fell north-westward, through Cumberland, towards Brampton. The 
upward movement brought hard and durable rocks of many different ages 
into contact with the softer rocks (the supposed Cretaceous Rocks). The 
date of the main upheaval was probably coincident with the great vol- 
canic episode, and probably also continued throughout nearly the whole 
of that period. 
In course of time the outer envelope disappeared from the uplands, 
leaving vestiges of its former presence in the gently inclined surface which 
the summit-level of the mountain areas evidently presents, from whatever 
elevated position we may regard it. The softer envelope would disappear 
latest in the parts where its base was nearest the sea level. Hence the 
very obvious plain extending from the foot of the Cross Fell Escarpment 
to Carlisle, thence northward gently rising to the Bewcastle Fells, and 
westward to the Solway. This plain is referred to generally as the Third 
Plain. The diagram-sections which accompany this chapter may serve 
to explain its nature better than any description. 
There are two other surfaces (or plains, as they might still be 
termed). The next older to the third plain is that upon which the New 
Red once lay. It was never very even in form, or perhaps it would be more 
correctly described as originally very uneven. But its re-exposure has 
left features on the outskirts of the Lake district which cannot well be 
mistaken. Lastly, there is the re-exposed surface upon which the Upper 
Old Red and the Carboniferous rocks at one time lay. Like the other 
two surfaces this has shared in all the disturbances that have affected the 
rocks in Post-Carboniferous times ; but its re-exposure has given rise to 
inclined surfaces on the outer margin of the Lake district which form 
important elements in the surface-relief. These three ‘plains’ or 
re-exposed rock-floors, embrace between them the whole of the broader 
surface-features of Cumberland, except the face of the Pennine Escarp- 
ment and the line of the coast. In other words, the whole of Cumberland 
consists of representatives of these three plains, more or less disturbed, 
and variously combined with each other. 
XII. Posr-Priocens CHANGES oF CiimaTE.—(az) One of the 
most important episodes in the geology of Cumberland is undoubtedly 
that connected with the long period of snow and ice which forms 
the closing chapters in the history of the past. The surface-features 
almost everywhere underwent considerable modification, lakes were ex- 
cavated where only river valleys were before, corries were scooped out 
of the mountain flanks, a vast and important series of glacial grooves 
was formed, crags and other irregularities of the surface were rounded 
off, the accumulated results of many thousands of years’ weathering were 
swept away, and, finally, nearly all the lowlands were covered with a 
mantle of boulder clay and other deposits of glacial origin. Important 
changes also took place in the elevation of the land whereby the form 
of the coast-line was greatly modified. Finally, biological changes, 
which have left their mark in many ways connected with the sequence 
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