Coastal Features and Landscapes (Litoral Zone)

  • Created by: Woden
  • Created on: 17-02-19 17:29

The Coast

backshore - area between high water mark and landward limit of marine activity. changes normally take place during storms 

foreshore - between high & low water mark and an important zone for marine activity 

nearshore - LSD occurs, between the low water mark & where the waves cease to effect the land beneath them 

offshore - beyond point of waves impacting land beneath, sediment is deposited 

littoral zone: wider coastal zone including adjacent land areas & shallow parts of the sea just offshore 

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Concordant Coastlines

Occurs where beds, or layers, of differing rock types are folded into ridges that run parallel to the coast. The outer hard rock provides a protective barrier to erosion of the softer rocks further inland. Sometimes the outer hard rock is punctured, allowing the sea to erode the softer rocks behind. This creates a cove, a circular area of water with a relatively narrow entrance from the sea.

E.g. West Dorset Coast: Lulworth Cove in Dorset is situated on a concordant coastline. The outer hard rock is Portland Limestone. The sea has broken through this barrier and easily eroded the clays behind it. A chalk cliff face at the back of the cove slows further erosion. Erosion is just starting to the west, where the sea has again broken through the Portland Limestone barrier at Stair Hole.

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Discordant Coastline

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.

E.g. East Dorset Coast: 

Part of the Dorset coastline in the UK 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 Swanage Bay where the rock type is a softer greensand.

North of Swanage, the chalk outcrop creates the headland which includes Old Harry Rocks.

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High Energy Coast

Where erosion>deposition

Waves have long fetches therefore are high energy, with a more powerful backwash than swash, meaning that they are destructive waves.

This will form a rocky coastline which result from resistant goelogy (to the erosive forces of sea, rain and wind), often in a high energy environment.

E.g. Holderness Coastline, Yorkshire

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Low Energy Coast

At these coastlines deposition>erosion

The waves here have a small fetch, therefore little energy, with more swash than backwash, meaning that they are construcive waves.

These form coastal plain landscapes (sandy and estuarine coasts) which are found near areas of low relief and result from supply of sediment from different terrestrial and offshore sources, often in a low energy environment.

E.g. Rhosilli Bay, Gower

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Isostatic Sea Level Change

Localised Sea Level Change

Brought about by the melting of glaciers, due to the end of the Ice Age.

The weight of the glaciers caused the continent to sink into the mantle, whilst where there was no glaicer the land rose up.

With the mass gone, the sunken land is now rising, and the risen land is now sinking into the mantle, this is called isostatic readjustment. 

E.g.  The southeast of the British Isles is sinking while the northeast is rising. This reflects that the ice sheets were thickest in northern Scotland and that this was the last area in the UK where the ice sheets melted. 

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Eustatic Sea Level Change

Global Change in Sea Level

Brought about by melting land ice and rising temperatures after the end of the Ice Age.

The melting land ice makes its way into the sea, therefore increasing the water contained there, thus increasing the level.

The increase in temperature leads to Thermal Expansion, which is when the water molecules have more energy, therefore the IMF (intermolecular forces) are not as strong, causing them to spread out.  This means that the water is less dense, so the same mass of water requires more space.

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