Geoscience Reference
In-Depth Information
Coastal shape and location
The spectacular 100 km long coastline is the defining feature of this South Coast Re-
gion. As outlined in Chapter 2, worldwide sea level was around 120 m lower than at
present only 18,000 years ago, and has been at or near its current level for only 5,000
years, at the most (Fig. 20). This means that the impressive coastal features that can be
examined along the South Coast today have formed within a very short space of time,
though some of them almost certainly involve relicts of earlier scenic features created
by previous high sea levels (for example during the Ipswichian, 130,000 years ago;
Fig. 13).
The overall east-west trend of the coastline is parallel to the folding that formed
during the mid Tertiary (see above). This is particularly so in the west, where these
folds have locally controlled the arrangement of the resistant Jurassic limestones and
the Late Cretaceous Chalk to produce spectacular, narrow headlands that dominate the
scenery. In the east of the Region, the coastline of Areas 6 and 7 swings northwards
and cross-cuts the mid-Tertiary folds, which themselves curve to the southeast and link
up with similar folds in the bedrock of northern France. This northwards curve of the
coastline was produced during low-sea-level conditions when a river flowed where the
English Channel is now, carving a wide valley through the bedrock structures. At the
end of the Ice Age cold episodes, the sea flooded this valley to create the English Chan-
nel (Fig. 21).
Another feature of the present coastline that strongly influences its local shape
is the presence of large accumulations of gravel in the form of active gravel spits.
Examples of these are Chesil Beach, Hurst Spit (5 km south of Lymington) and Dunge-
ness. In all these cases, the gravel accumulations appear to have been transported into
this area by powerful rivers during Ice Age times, and are now being reworked and re-
shaped by modern-day wave action.
AREA 4: EAST DEVON, SOMERSET AND DORSET
This area (Figs 97 and 98) includes most of the Jurassic Coast, a stretch of the coastline
that became a World Heritage Site in 2001. This coast holds a special place in the his-
tory of geological discovery, providing a beautifully varied and colourful range of bed-
rocks that cover some 250 million years of the Earth's history. It is famous for Jurassic
fossil collecting and also provides a laboratory for studying coastal erosion, land-slip-
ping and sedimentation processes, as well as for exploring the natural history of the
coastal zone. Oil-producing rocks are also visible along the coast and oil is currently
being extracted from parts of southeast Dorset (at Wytch Farm - see Area 5).
