Geomorphology & Coastal Processes

The geomorphology expressed on the Jurassic Coast itself is connected to landforms inland as well as on the seabed, which have been shaped (and will continue to be shaped) by the wider marine and terrestrial processes. The appearance of the Site is largely defined by sub-aerial processes (rain, frost, wind, and streams, among others) which sculpted the present landscape, for example the valleys between Worbarrow Tout via Lulworth to White Nothe.

Furthermore, the geology of those cliffs reveals very recent (in geological time-scales) Earth surface processes. Similarly, many of the present-day landslides depend on groundwater draining to the coast from catchments inland.

Offshore, the processes which shape the coast and affect its dynamics exist in a zone of variable width where waves influence sediment movement both onshore-offshore and alongshore, as well as in areas in which currents transport sediment, mainly sand, on-and offshore.

---

Processes and landforms along the Jurassic Coast

The cliffs are at one and the same time both dynamic and unchanging.  The long geological history of this coast has produced rocks and structures which are varied in age, alignment and strength on which the forces of sea and air, and occasionally humans, have worked to erode and mould the present coastal landscape.

The wide variety of landforms and processes that occur along the Jurassic Coast enable a great diversity of marine and coastal habitats.  The sea cliffs support varied plant and invertebrate communities of particular conservation significance. Underwater, this is also a diverse and dynamic landscape, on which sand and pebbles are moved by the waves and currents and sometimes cover existing rocky outcrops.  

Internationally renowned erosional features include Lulworth Cove, Stair Hole, Worbarrow Bay, Durdle Door and Old Harry Rocks.  Chesil Beach is recognised as a unique shingle and cobble ridge supplied by eroding cliffs which and separates the equally important Fleet, one of Britain’s few lagoons, from the sea.

Aspects of the ancient geomorphological history are preserved on hill-top surfaces at White Nothe and in East Devon.  Some landforms directly influence the Site’s  character as seen from the sea, especially hanging Chalk dry valleys and small coastal valleys, e.g. Winspit.  The inland features, notably in Purbeck, show how the underlying rocks influence the landscape of the Site and its evolution.

Although the coastal streams and rivers influence the overall shape of the landscape, they supply hardly any sediment to present-day beaches.  Typically streams are deflected at their mouths by longshore sediment movements or flow directly through shingle ridges.  Occasional flooding may breach these ridges and alter the position of the river mouth.