Coastal Key Terms

Front 1

Abrasion/Corrasion

Back 1

The wearing away of cliffs by sediment flung by breaking waves.

Front 2

Arch

Back 2

wave-eroded passage through a small headland. This begins as a cave formed in the headland, which is gradually widened and deepened until it cuts through.

Front 3

Attrition

Back 3

erosion caused when rocks and boulders transported by waves bump into each other and break up into smaller pieces becoming rounder and smoother.

Front 4

Backwash

Back 4

the return of water to the sea after waves break on a beach.

Front 5

Bar

Back 5

where a spit grows across a bay. A bar can eventually enclose the bay to create a lagoon.

Front 6

Beach

Back 6

the temporary deposition of sand and shingle along the coastline. Without its beach a coast is vulnerable to erosion.

Front 7

Biological Weathering

Back 7

the breakdown of rock through the action of plants and animals.

Front 8

Breakwaters

Back 8

offshore coastal defence structures built of stone parallel to the coastline; they help absorb the energy of breaking waves. Deposition occurs in the calmer water created behind the breakwater.

Front 9

Cave

Back 9

found in coasts formed of resistant rock. Corrasion, Corrosion and Hydraulic action widen any weakness within the rock e.g. joint, bedding plane or fault, to form a cave.

Front 10

Chemical Weathering (solution)

Back 10

the decomposition (or rotting) of rock caused by a chemical change within that rock; sea water causes chemical weathering of cliffs.

Front 11

Concordant Coastlines

Back 11

a coastline that has the same type of rock along its length. They tend to have fewer bays and headlands.

Front 12

Constructive Waves

Back 12

found on low-angled beaches and mainly responsible for coastal deposition. They are gently breaking, with a much stronger swash than backwash.

Front 13

Destructive Waves

Back 13

found on steep beaches, are steeply breaking and mainly responsible for coastal erosion. Their backwash is much stronger than their swash.

Front 14

Discordant Coastlines

Back 14

Coastlines where the geology alternates between strata (or bands) of hard rock and soft rock.

Front 15

Dredging

Back 15

excavating sand and shingle from the sea bed; this can contribute to coastal erosion.

Front 16

Exfoliation/Onion Weathering

Back 16

a form physical weathering that occurs in very warm climates when a rock is repeatedly heated and cooled.

Front 17

Fetch

Back 17

the maximum distance of water over which winds can blow. In the case of south-west England the maximum fetch is from the south-west (5000 miles). This also coincides with the direction of the prevailing wind and leads to large storm waves attacking Barton on Sea, particularly in Winter.

Front 18

Freeze-Thaw Weathering/frost-shattering

Back 18

it occurs in cold climates when temperatures are often around freezing point and where exposed rocks contain many cracks. Water enters the cracks during the warmer day and freezes during the colder night. As the water turns into ice it expands and exerts pressure on the surrounding rock, causing pieces to break off.

Front 19

Gabions

Back 19

steel wire mesh filled with boulders used in coastal defences.

Front 20

Groyne

Back 20

a wooden barrier built out into the sea to stop the longshore drift of sand and shingle, and so cause the beach to grow. It is used to build beaches to protect against cliff erosion and provide an important tourist amenity. However, by trapping sediment it deprives another area, down-drift, of new beach material.

Front 21

Headlands

Back 21

areas of land protruding out to sea formed of resistant (harder) rock. They help protect the bay which forms between them from wave attack.

Front 22

Hydraulic Pressure

Back 22

the process by which breaking waves compress pockets of air in cracks in a cliff. The pressure may cause the crack to widen, breaking off rock.

Front 23

Hard Engineering

Back 23

the process of controlled disruption of natural process by use of man-made techniques. Some of the examples of hard engineering are Wooden Groynes, Gabion Groynes, Rock Armour / Rip Rap. These options tend to be very expensive, have high impact and tend to be extremely obvious.

Front 24

Lagoon

Back 24

a former bay cut off from the sea by a bar.

Front 25

Land Reclamation

Back 25

areas of land that were once below the sea; the sea has either been blocked off by dykes and the sea water pumped out (e.g. Dutch Polders), or material has been dumped into the sea to raise the level of the seabed until it becomes dry land.

Front 26

Longshore Drift

Back 26

waves approaching the coast at an angle result in the gradual zig-zag movement of beach materials along the coast.

Front 27

Managed Retreat

Back 27

allowing cliff erosion to occur as nature taking its course: erosion in some areas, deposition in others. Benefits include less money spent and the creation of natural environments.

Front 28

Mass Movement

Back 28

the downhill movement of weathered material under the force of gravity. The speed can vary considerably, from soil creep, where the movement is barely noticeable, to slumps, slides and mudflows, where the movement becomes increasingly more rapid.

Front 29

Physical Weathering

Back 29

the disintegration of rock into smaller pieces without any chemical change in the rock; this is most likely in areas of bare rock where there is no vegetation to protect the rock from extremes of weather e.g. freeze-thaw and exfoliation (or onion weathering).

Front 30

Prevailing Wind

Back 30

the direction from which the wind usually blows.

Front 31

Revetments

Back 31

wooden, steel, or concrete fence-like structures that allow sea water and sediment to pass through, but the structures absorb wave energy. A beach can build up behind the revetment and provide further protection for the cliff. These are used as part of coastal defences.

Front 32

Rip-Rap

Back 32

large boulders dumped on the beach as part as part of coastal defences.

Front 33

Sea Walls

Back 33

aim to prevent erosion of the coast by providing a barrier which reflects wave energy.

Front 34

Slumping

Back 34

involves a whole segment of the cliff moving down-slope along a saturated shear-plane.

Front 35

Spit

Back 35

a long, narrow accumulation of sand and shingle formed by longshore drift and deposited where the coastline abruptly changes direction. One end of the spit is connected to the land and the other end projects out to the sea, often with a curved (hooked) end.

Front 36

Soft Engineering

Back 36

the use of ecological principles and practices to reduce erosion and achieve the stabilization and safety of shorelines, while enhancing the habitat, improving aesthetics, and also saving money. It is achieved through use of vegetation and other materials to soften the land-water interface, thus improving ecological features without compromising the engineered integrity of the shoreline.

Front 37

Stack

Back 37

rock left standing out at sea after wave erosion has separated it from the mainland. This is the next stage from an arch. Waves will continue to erode the foot of the arch until its roof becomes too heavy to be supported. When the roof collapses, it will leave part of the former cliff isolated.

Front 38

Stump

Back 38

formed by continuing wave action attacking a stack until it collapses.

Front 39

Swash

Back 39

forward movement of a wave up a beach.

Front 40

Tombolo

Back 40

a spit joining an island to the mainland.

Front 41

Wave Cut Platform

Back 41

a gently sloping, rocky platform found at the foot of an eroding cliff and exposed at low tide.