Location and Formation of a Coastal Landscape

This unique physical landscape drives immense human and economic significance. The coastline receives approximately 24.4 million visits per year, supporting 35,000 to 47,000 jobs (10-13% of all local employment). The tourism industry contributes a massive £1.76 billion annually to the Dorset economy, making the preservation of this landscape critical.

How Geological Structure Shapes the Coastline

You can easily mold wet clay in your hands, but trying to snap a block of solid limestone is almost impossible. This difference in lithology (the physical characteristics and resistance of rocks) dictates the shape of the entire coastline.

The southern side of the Jurassic Coast is a Concordant Coastline, where rock bands run parallel to the shore. Near Lulworth, the sea first meets resistant Portland Limestone, followed by moderately resistant Purbeck Limestone, less resistant Wealden Clay, Greensand, and finally resistant Chalk. In addition, immense tectonic pressure during the Alpine Orogeny caused a major rock fold called the Purbeck Monocline, tilting the rock strata and creating the folded beds known as the "Lulworth Crumple."

Conversely, the eastern side features a Discordant Coastline, where rock bands run perpendicular (at right angles) to the shore. Here, differential erosion creates alternating headlands and bays. Destructive waves quickly erode the less resistant Wealden Clay via hydraulic action to form Swanage Bay, while the resistant Chalk erodes much more slowly, left protruding out to sea as a steep headland called The Foreland.

Physical Processes Driving Landscape Change

Why do some coastlines face massive, destructive waves while others are perfectly calm? The Jurassic Coast has a South/South-Westerly aspect, facing directly into the UK's prevailing winds.

It experiences a long fetch of over 3,000 miles extending across the South Atlantic. Because wave energy increases exponentially with height ($E \propto LH^2$), this massive fetch generates powerful, high-energy destructive waves that constantly batter the shoreline. Driven by the prevailing South-Westerly winds, sediment at Swanage is continually transported from South to North in a zig-zag motion via longshore drift.

Simultaneously, the cliff faces are weakened by sub-aerial processes such as weathering and mass movement above the high-tide mark. Mechanical weathering like freeze-thaw shatters resistant Chalk, while chemical weathering targets limestone through carbonation:

$$H_2O + CO_2 + CaCO_3 \rightarrow Ca(HCO_3)_2$$

Once weakened, heavy rainfall can trigger severe mass movement. At Black Ven, porous limestone sits on top of impermeable clay. Rain saturates the limestone, lubricates the clay to create a slip plane, and gravity triggers dramatic rotational slumping, forming Europe's largest mudslides.

Formation of Distinctive Coastal Landforms

Understanding how wave energy concentrates and spreads explains exactly why specific coastal shapes form. At Lulworth Cove, waves eventually breached a fault in the highly resistant Portland Limestone, creating a narrow entrance. Once through, wave diffraction caused the waves to spread out into an arc, rapidly eroding the less resistant Wealden Clay behind it to form a wide, circular cove.

Further east at Old Harry Rocks, marine erosion has carved a classic sequence of coastal landforms into a resistant Chalk headland. Destructive waves exploited faults to form caves, which broke through into arches, eventually collapsing to leave isolated stacks (Old Harry) and stumps (Old Harry's Wife, which collapsed in 1896).

In contrast, Chesil Beach is an extraordinary depositional landform. It is an 18-mile-long tombolo (barrier beach) reaching heights of 15 metres. By connecting the Isle of Portland to the mainland, it encloses the low-relief, low-energy Fleet Lagoon behind it.

Factors Influencing Contemporary Landscape Change

Every time a major winter storm hits the UK, the coastline can change dramatically overnight. Climate heavily dictates the rate of coastal retreat; during the 2014 Valentine's Day Storm, 80 mph winds and 30-foot waves breached sea defences at Chesil Beach and caused the famous "Pom Pom" rock to collapse entirely.

Human intervention also drastically alters how the landscape changes. At Lyme Regis, a massive £43 million environmental improvement scheme involved hard engineering, including 390m of new sea walls and pinning the cliffs with 19m long steel nails. Meanwhile, Swanage underwent soft and hard engineering, installing 18 timber groynes and spending £2.2 million on beach nourishment (adding 90,000 m³ of sand).

However, human activity often creates negative impacts or management conflicts. High visitor numbers cause trampling, which wears down footpaths and destroys protective vegetation on chalk cliff tops. Furthermore, groynes built at Swanage successfully protect the town but "starve" beaches further north of sediment, ultimately increasing erosion rates further down the coast.