68
THE INTER-RELATIONS OF
rounded hills with steep-sided coombs and streamless valleys.
A Carboniferous Limestone district will present perpendicular cliffs,
deep river gorges, and large underground cavities, as the cliffs of
Cheddar and the Mendip caves, and the tors and caverns of Derby-
shire. The Triassic New Red Sandstone and Marls give the great
Midland plains of England and the broad Vale Royal of Cheshire.
If hard coast rocks have formed the seaward boundary of glacier-
laden lands, the coast-line will be deeply indented by incut fiords or
inlets, as the west coast of Norway, the west and north coasts of Ice-
land, and the west loch-indented coast of Scotland. When a long
coast-line mainly composed of comparatively soft rocks is varied
by occasional hard strata, the harder rocks will form headlands
and projecting capes, while broad open bays and sweeping con-
figuration will characterise the coast, as the east coast of England
with Flamborough Head and Scarborough Castle Rock.
The great upheaval of Central Europe in Post-Eocene times
gave to the Alps their great elevation, and their "cloud compelling"
tops thus became the depositories for those immense accumulations
of snows which give the river-producing glaciers of the present
Switzerland, and the lake-producing glaciers of pre-historic times.
These same Alps have by the disintegration of the rocks of their
southern precipitous faces furnished the material that filled up an
arm of the sea and now underlies and forms the great Plain of
Lombardy, carrying the Po onward and eastward to the now distant
Adriatic.
On a smaller scale, too, geological structure determines surface
features.
Hard igneous rock that has been ejected through softer beds as
lava will often be the cause of isolated hills being left standing in a
plain. Arthur's Seat and the Castle Hill of Edinburgh are well known
examples, and a less known instance, though a very beautiful and
suggestive illustration, is that of the Clee Hills in Shropshire, where
a capping of hard volcanic rock has preserved the underlying rocks
from denudation, and with them a small coal-field, which has been
worked, that without the overlying igneous mass would not now be
in existence. To Palaeozoic volcanic action we owe some of the
finest and greatest physical features of Great Britain, for Snowdon,
and Cadir Idris, and much of the mountain land of the beautiful
Lake District of Cumberland and Westmoreland are due to the pro-
tecting existence of hard volcanic rock.