Geoscience Reference
In-Depth Information
this slope may reflect the way the weak mud material of the Weald Clay has tended to
collapse and flow down-slope.
As the coastal town of Hythe is approached, the Weald Clay bedrock becomes
covered up by the surface blanket of Romney Marsh. The area underlain by the Weald
Clay generally becomes much narrower in Area 7, at least partly because the total
thickness of the Clay in the bedrock succession decreases here to just over 100 m, com-
pared with some 500 m near Guildford in Area 11. Changes of thickness of this sort
usually reflect variations in the downward movements of the Earth's crust during the
accumulation of the sediment, but may also reflect variations in the amount of sedi-
ment supplied to the environment in which the Weald Clay accumulated.
Landscape C: The Wealden Greensand
Coastal erosion in the Hythe and Folkestone area has produced vegetated cliffs cut into
Early Cretaceous Lower Greensand and Gault bedrocks (Fig. 142). These units have a
combined thickness of about 150 m in the Folkestone area and consist largely of mud-
stones, except for a lower sandstone layer (the Hythe Beds) and an upper sandstone
layer (the Folkestone Beds). The sandstones have preferentially resisted erosion to pro-
duce slopes in the local scenery, particularly in the case of the Hythe Beds, which con-
tain thin, hard limestone layers inter-bedded with sandstones containing grains of the
dark green, iron-bearing mineral glauconite. These alternations of hard and soft bands
were known as 'rag and hassock' by local quarrymen in earlier times, and 'Kentish
Rag' is still a source of road stone and concrete aggregate.
The Hythe beds have been eroded into a distinct scarp for some 10 km along the
northern margin (
c1
) of Romney Marsh, west of Hythe. In more recent times, the mar-
gin of this scarp has been made less distinct by land-slipping and surface modification,
as the Hythe Bed sandstones have collapsed downwards over the underlying softer
mudstones.
