Geoscience Reference
In-Depth Information
swampy river conditions. Similar beds have not been found further downstream, sug-
gesting that downward movement and marine conditions were more continuous there.
One fascinating feature of the shoreline of this Landscape is the Medway Estuary,
which is remarkable for its width and its large number of islands. Most of the islands
appear to have grown recently as mud and sand have been brought into the estuary by
the tides, creating isolated salt marshes and other expanses of intertidal sediment. The
width of the estuary suggests that it formed under Ice Age conditions, prior to the re-
cent rise in sea level, as an extensive, flat-lying lowland. This lowland area may have
grown in size through freeze-thaw slumping of its hilly margins, similar to the areas
of south Essex described below (Landscape
D
). In the aerial photograph (Fig. 220),
Rochester's Norman castle and cathedral can be seen in the foreground, overlooking
the River Medway.
FIG
220.
The Medway river and estuary, with Rochester castle and cathedral. (Copyright
Dae Sasitorn & Adrian Warren/www.lastrefuge.co.uk)
The rising sea level did not just flood valleys and streams. Sea storms moved large
quantities of soft sand and mud, which were then deposited against the new coastlines.
The ancestral Thames and its associated tributaries also supplied large quantities of
mud and sand to the coastline, transported from further upstream. Plants stabilised the
sediment, and eventually it developed into wide expanses of salt marsh and estuarine
mud flats.
The efforts of humankind have also had a large impact on the estuary: man-made
sea walls encourage the deposition of sand and mud, accelerating the growth of the salt
marshes and mud flats. The new land is reclaimed from the sea and new sea walls are
