Discordant coastline

Durlston Head (limestone) to Handfast Point (chalk), with Peveril Point (limestone) dividing Durlston Bay from Swanage Bay

A discordant coastline occurs where bands of different rock type run perpendicular to the coast.

The differing resistance to erosion leads to the formation of headlands and bays. A hard rock type such as granite is resistant to erosion and creates a promontory whilst a softer rock type such as the clays of Bagshot Beds is easily eroded creating a bay.

Part of the Dorset coastline running north from the Portland limestone of Durlston Head is a clear example of a discordant coastline. The Portland limestone is resistant to erosion; then to the north there is a bay at Swanage where the rock type is a softer greensand. North of Swanage, the chalk outcrop creates the headland which includes Old Harry Rocks.

The converse of a discordant coastline is a concordant coastline.

Examples

The coastline around Swanage (50°36′24″N 1°57′54″W / 50.60667°N 1.96500°W / 50.60667; -1.96500) is an example of a discordant coastline.

Coastal geography

Landforms	Anchialine pool Archipelago Atoll Avulsion Ayre Barrier island Bay Baymouth bar Bight Bodden Brackish marsh Cape Channel Cliff Coast Coastal plain Coastal waterfall Continental margin Continental shelf Coral reef Cove Dune cliff-top Estuary Firth Fjard Fjord Freshwater marsh Fundus Gat Geo Gulf Gut Headland Inlet Intertidal wetland Island Islet Isthmus Lagoon Machair Marine terrace Mega delta Mouth bar Mudflat Natural arch Peninsula Reef Regressive delta Ria River delta Salt marsh Shoal Shore Skerry Sound Stack Strait Strand plain Submarine canyon Tidal island Tidal marsh Tide pool Tied island Tombolo Windwatt

Beaches	Beach cusps Beach evolution Beach morphodynamics Beach ridge Beachrock Pocket beach Raised beach Recession Shell beach Shingle beach Storm beach Wash margin

Processes	Blowhole Cliffed coast Coastal biogeomorphology Coastal erosion Concordant coastline Current Cuspate foreland Discordant coastline Emergent coastline Feeder bluff Fetch Flat coast Graded shoreline Headlands and bays Ingression coast Large-scale coastal behaviour Longshore drift Marine regression Marine transgression Raised shoreline Rip current Rocky shore Sea cave Sea foam Shoal Spit Steep coast Submergent coastline Surf break Surf zone Surge channel Swash Undertow Volcanic arc Wave-cut platform Wave shoaling Wind wave Wrack zone

Management	Accretion Coastal management Integrated coastal zone management Submersion

Related	Bulkhead line Grain size boulder clay cobble granule pebble sand shingle silt Intertidal zone Littoral zone Physical oceanography Region of freshwater influence

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Discordant coastline

Examples

See also