Wave action and coastal landforms PART TWO Yesterday

Wave action and coastal landforms PART TWO!

Yesterday, we learned about… �Waves friction �Wave length, height, crest, trough �Wave action: constructive and destructive �Swash and backwash �Longshore drift �Wave refraction

Coastline Erosion �Four 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 seawater �There 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/geogra phy/coastalprocessesrev 3. shtml

Corrasion/ Abrasion �Scouring of the rock �Sand rock particles in waves wear down rock surfaces (usually at the base of a cliff) �Leaves rock very smooth �Like sandpaper http: //www. bbc. co. uk/schools/gcsebitesize/geography/ coastal/coastalprocessesrev 3. shtml

Attrition �Rock particles in suspension erode each other �Rock hits rock particles break down �Hitting each other and getting smaller in size http: //www. bbc. co. uk/schools/gcsebitesize/geography/ coastal/coastalprocessesrev 3. shtml

Hydraulic Action �When 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/coastalprocessesrev 3. shtml

Undercutting (52 -53) �Rock eroded and removed at the base of a cliff �Creates a very steep, vertical cliff

Cliff erosion features �Caves �Bays �Headlands �Tunnels �Arches �Stacks �Wave-cut platforms

Caves, Bays, Headlands �CAVES: 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 refraction �Stack: isolated rock pillar after arch caves �Wave-cut platform: undercutting creates a rock debris platform in water http: //www. geography. learnontheinternet. co. uk/topics/coas ts_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

Tombolo �When 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 sea �Fjord: Lower part of U 0 shaped valley flooded with water �Estuary: 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 Protection � 1) Sea wall: man-made wall to prevent wave erosion � 2) Groynes: artificial barriers built into ocean to stop movement of sand by longshore drift