2.4 How do coastal processes shape the land? Part B

What landforms are created by coastal processes? A Erosional landforms Blow-hole Sea arch Geo Stack Sea cliff Sea cave Wave-cut platform

What landforms are created by coastal processes? B Depositional landforms Beach Spit Bar Tombolo

Is wave action the only factor in shaping the coast? No, there are several factors interacting with each other to create coastal landforms.

Subject to active wave erosion Uplifting (or lowering) of land Is wave action the only factor in shaping the coast? 1 Tectonic movement Subject to active wave erosion Tectonic movement can cause land to rise or fall. The uplifting or lowering of the coastline changes the zone of active wave erosion. Sea Uplifting (or lowering) of land Plate Compressional force

Is wave action the only factor in shaping the coast? 2 Nature of rocks Horizontal bedding plane Wave undercutting enlarges the notch and causes collapse of rock above the notch. Parallel retreat of cliffs is resulted. Land Sea Notch

Is wave action the only factor in shaping the coast? 2 Nature of rocks Bedding plane dipping seawards Rocks loosened by wave erosion and mass movement slide down along the bedding plane. Sea Land

The slope is more resistant to wave erosion. Is wave action the only factor in shaping the coast? 2 Nature of rocks Bedding plane dipping landwards The slope is more resistant to wave erosion. Sea Land

Is wave action the only factor in shaping the coast? 3 Weather and climate Global warming leads to a rise in sea levels because of the thermal expansion of water and melting of polar ice caps. Changes in sea levels are changing the position of the zone of active wave erosion.

Is wave action the only factor in shaping the coast? 3 Weather and climate A warmer world would generate more storm surges, thereby affecting coastal landforms.

Is wave action the only factor in shaping the coast? 4 Fluvial processes Rivers bring sediment to the coast as they flow to the sea. Delta Deposition occurs at the coast where wave action is weak. Sediment may gradually build up to form depositional landform such as a delta. River Nile Red Sea The River Nile, Africa (Credit: NASA)

Is wave action the only factor in shaping the coast? 5 Marine organisms Some marine organisms protect the coast from wave erosion and favour deposition. Mangroves For example, coral reefs and mangroves.

What landforms are created by coastal processes? A Erosional landforms Sea cliffs and wave-cut platforms Undercutting continues and the notch is enlarged. The overhanging part above the notch collapses. It forms a sea cliff. A notch is formed by undercutting. Waves repeatedly pound against the coast. The waves erode the part of the coast between high tide and low tide.

What landforms are created by coastal processes? A Erosional landforms Sea cliffs and wave-cut platforms Over time, a gently sloping or flat surface called a wave-cut platform is developed at the base of the sea cliff. Erosion continues, the sea cliff retreats inland.

What landforms are created by coastal processes? A Erosional landforms Sea cliffs and wave-cut platforms Sea cliff Wave-cut platform Ping Chau in Mirs Bay

What landforms are created by coastal processes? A Erosional landforms Sea caves and geos Block diagram Cross-section Sea Land High tide level Low tide level Line of weakness Geo Sea cave Collapse of cave roof Sea cave When waves splash against the roof of a narrow sea cave, the roof may collapse. A geo is formed. A line of weakness in the cliff is exposed to waves. Active wave erosion widens the line of weakness to form a sea cave.

What landforms are created by coastal processes? A Erosional landforms Sea caves and geos A sea cave in Sai Kung A geo in Sai Kung

What landforms are created by coastal processes? A Erosional landforms Sea arches and stacks This leaves a mass of rock with steep sides standing offshore. This is the stack. Further erosion may cause the sea arch to collapse. When a sea cave gets eroded from time to time, it might cut through to form a sea arch.

What landforms are created by coastal processes? A Erosional landforms Sea arches and stacks A sea arch and a stack in Canada (Credit: Getty Images)

What landforms are created by coastal processes? A Erosional landforms Blow-holes A vertical or near vertical tunnel is formed along the vertical weakness as a blow-hole. When waves break into the sea cave, hydraulic action of waves takes place along the vertical weakness in it. A sea cave is developed along a horizontal line of weakness. w

What landforms are created by coastal processes? A Erosional landforms Blow-holes Halona Blow-hole in Hawaii (Credit: Getty Images) During storms, waves breaking into the sea cave may force water or just air out of the blow-hole.

What landforms are created by coastal processes? B Depositional landforms Beaches Wave energy is dispersed in sheltered bays. Deposition takes place to form beaches. Sand and shingle are built up between the lowest and the highest water levels.

What landforms are created by coastal processes? B Depositional landforms Beaches Waikiki Beach, Hawaii

Materials are built up to form a spit What landforms are created by coastal processes? B Depositional landforms Spits The sediment accumulates and builds up into a spit, with one end attached to the land, and the other end extending out to the sea. Materials are transported along the coast by longshore drift. Wind direction Change of coastline Land Marshland Longshore drift Longshore drift Materials are built up to form a spit Where the coastline changes, the materials are deposited in slack water. Area behind the spit is of low energy, mud and marshland begins to develop Spit extends Sea The spit extends as sediment continues to accumulate. Wave crest Longshore drift

End of the spit is bent or recurved What landforms are created by coastal processes? B Depositional landforms Spits A Spit in Greece As the waves are refracted, the end of the spit becomes hooked. Land Marshland Longshore drift spit Sea Longshore drift End of the spit is bent or recurved Wave crest (Credit: Corbis)

What landforms are created by coastal processes? B Depositional landforms Bars When a spit develops and extends across a bay, a bar is formed. A lagoon is formed behind the bar.

What landforms are created by coastal processes? B Depositional landforms Bars Chesil Beach in England is formed from a bar (Credit: Corbis)

What landforms are created by coastal processes? B Depositional landforms Tombolos When the spit builds up and joins an island to the mainland or two islands together, a tombolo is formed.

What landforms are created by coastal processes? B Depositional landforms Tombolos The Cheung Chau tombolo is formed when two spits join together.