Geoscience Reference
In-Depth Information
Review of the landscape history
Most of the inland slopes and valleys have been created during the evolution of the
river and stream systems that occupy the valley bottoms. These systems have not only
drained the landscapes, but they have also generated sediment as they have eroded and
carried it away, causing an overall lowering of the ground surface.
FIG
123.
Main river pathways and coastal flooding zone for Area 5.
The present-day drainage provides a template for this key aspect of the landscape
evolution, though the exact locations of the rivers will have changed considerably over
time. We can simplify the pattern by selecting the main valleys and labelling them as
the 'main river pathways', as in Figure 123. This general pattern is likely to be over 20
million years old.
The coastline of this area has taken up its familiar form and position only in the
last few thousand years. During the previous 12,000 years, the coastline has advanced
inland great distances because of a rise in sea level of about 120 m, due to the melting
of the ice sheets formed during the last cold episode of the Ice Age.
At the time of the Devensian Glacial, about 20,000 years ago, a continuous belt
of hilly ground underlain by Chalk extended across most of the southern part of Area
5 (now largely covered by the sea), from an area south and east of the present Isle of
Wight to the present Isle of Purbeck. The headland of Culver Cliff at the eastern end of
