Wave action and coastal landforms

PART TWO!

Yesterday, we learned about…Waves frictionWave length,

height, crest, trough

Wave action: constructive and destructive

Swash and backwash

Longshore driftWave refraction

Coastline ErosionFour types:

1) Corrosion

2) Corrasion/ Abrasion

3) Attrition

4) Hydraulic action

Corrosion (also sometimes called solution)A type of chemical weathering where

material is dissolved by seawaterThere are weak acids in the sea which wear

rock down (especially some types of rock such as chalk or limestone)

http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalprocessesrev3.shtml

Corrasion/ AbrasionScouring of the rockSand and rock particles in waves wear

down rock surfaces (usually at the base of a cliff)

Leaves rock very smoothLike sandpaper

http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalprocessesrev3.shtml

AttritionRock particles in suspension erode each

otherRock hits rock particles break downHitting each other and getting smaller in size

http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalprocessesrev3.shtml

Hydraulic ActionWhen waves hit the base of a cliff, air is

compressed into cracks. When the wave retreats the air rushes out of the gap cliff material breaks away.

Basically, water and air are compressed into rock fractures water and air in and out of the rock breaks it apart

http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalprocessesrev3.shtml

Undercutting (52-53)Rock eroded and removed at the base of a

cliff Creates a very steep, vertical cliff

Cliff erosion featuresCavesBaysHeadlandsTunnelsArchesStacksWave-cut platforms

Caves, Bays, HeadlandsCAVES: Indentation in the

weakest rock surface of cliff caused by wave refraction and hydraulic action

BAYS: soft rock wears away faster bay between headlands

HEADLANDS: Hard rock more resistant to erosion erodes into jagged shape that juts out from land

Erosion of cliffs caves bays and headlands caves tunnels arch stack wave-cut

platform

Arch: hole in headland caused by wave refractionStack: isolated rock pillar after arch cavesWave-cut platform: undercutting creates a rock

debris platform in water

http://www.geography.learnontheinternet.co.uk/topics/coasts_erosional_landforms.html#baysandheadlands

Shoreline depositional features

Spits

Tombolos

Spit Long ridge of sand created by longshore

drift

Linear accumulation of sediment attached to land at one end.

Spits are typically elongate, narrow features built to several dozen feet by wind and waves.

Where there is an obstruction or the power of the waves is reduced the material is deposited. The sediment which is deposited usually builds up over the years to form a long ridge of material

TomboloWhen sand spit

grows long enough that it joins an island to the mainland

Types of coasts (54) Ria: lower part of V-shaped valley flooded

with water A drowned river valley that remains open to

the seaFjord: Lower part of U0shaped valley flooded

with waterEstuary: lower part of a river valley filled

with sediment and submerged by the sea depending on the tides; mix of salt and fresh water; funnel shape with gently sloping sides

Ria

Coastal Protection1) Sea wall: man-made wall to prevent wave erosion

2) Groynes: artificial barriers built into ocean to stop movement of sand by longshore drift