Coasts
| coasts.pdf |
Waves
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Answer the following questions:
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- Crest: The top of the wave.
- Trough: The low area in between two waves.
- Wavelength: The distance between two crests or two troughs.
- Wave height: The distance between the crest and the trough.
- Wave Frequency: The number of waves per minute.
- Velocity: The speed that a wave is traveling. It is influenced by the wind, fetch and depth of water.
- Swash: The movement of water and load up the beach.
- Backwash: The movement of water and load back down the beach.
Types of waves
Constructive
Small oceans with small fetch develop constructive waves. Constructive waves have low wave height and long wave length with low frequency, between 6 and 8 waves per minute. Constructive waves are associated with weak backwash and strong swash, which builds up wide flat beaches and so more associated with coasts of deposition. Constructive waves also tend to form sandy beaches.
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Destructive
Destructive Waves
Large oceans with large fetch produce large waves, called destructive waves. These waves have large wave height and short wave length and are characterised by tall breakers that have high downward force and a strong backwash. They have high frequency, between 13 and 15 waves per minute. This downward energy helps erode cliifs. In addition, due to a dominant backwash they erode the beach making for narrow steep beach profiles. Localised storms with high wind speed also form destructive waves as well as steep depth gradients around headlands. Destructive waves also tend to form pebbly beaches.
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Marine Processes
Erosion
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Four Types of Coastal Erosion:
Hydraulic action (pressure): This is when sea water and air get trapped in cracks. The increasing pressure of the water and air cause the rocks to crack. It can also be the shear force of the wave pounding on the coast. Corrasion (abrasion): Rocks been thrown into the cliffs by waves and breaking off bits of the cliff. Corrosion (solution): The slight acidity of sea water causing bits of the cliff to dissolve. Attrition: Rocks, sand and stones being thrown into each other by the sea current and waves. |
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Marine Transportation
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Longshore Drift (LSD)
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Deposition
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When the sea loses energy, it drops the sand, rock particles and pebbles it has been carrying. This is called deposition. Deposition happens when the swash is stronger than the backwash and is associated with constructive waves.
Deposition is likely to occur when:
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Erosional Landforms
The land-forms that are created by erosion on the coast depend on:
- Rock type (Hard or Soft rock)
- Bedding Planes
Concordant CoastsA concordant coast occurs where beds, or layers, of differing rock types are folded into ridges that run parallel to the coast. The outer hard rock (for example, granite) provides a protective barrier to erosion of the softer rocks (for example, clays) 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.
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DISCORDANT CoastsA 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. A hard rock type such as granite is resistant to erosion and creates a promontory whilst a softer rock type such as the clays of Bagshot Beds is easily eroded creating a bay. 
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Wave cut platforms
Example of a wave cut platform
Wave cut platforms - process
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One of the most common features of a coastline is a cliff. Cliffs are shaped through a combination of erosion and weathering - the breakdown of rocks caused by weather conditions.
Soft rock, eg sand and clay, erodes easily to create gently sloping cliffs. Hard rock, eg chalk, is more resistant and erodes slowly to create steep cliffs. Forming a wave cut platform
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Caves, arches, stacks and stumps
Caves, arches, stacks and stumps
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Stages of formation:
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DEPOSITIONal Landforms
Beaches
Beach: Is an accumulation of sediment, usually found in a bay. Beaches can be made out of sand, shingle and/or pebbles. Beaches receive their material from longshore drift, constructive waves, cliff erosion and river discharge. All beaches are depositional landforms but if they are made out of sand they have more depositional characteristics than if they are made from shingle and/or pebbles.
Beaches cane be divided into backshore, offshore and foreshore. The backshore is the area above the normal high tide level, the foreshore is the area in between normal high and low tide. The Berm is a ridge (long thin hill) that forms at the top of the foreshore. It is basically sand accumulated on the strand line (twigs, litter, seaweed, etc. deposited at high tide).
Beaches cane be divided into backshore, offshore and foreshore. The backshore is the area above the normal high tide level, the foreshore is the area in between normal high and low tide. The Berm is a ridge (long thin hill) that forms at the top of the foreshore. It is basically sand accumulated on the strand line (twigs, litter, seaweed, etc. deposited at high tide).
Beach diagram
Spits
Spit Diagram
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Farewell Spit, New Zealand
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- The prevailing wind and waves approach the coast at an angle.
- This causes Long Shore Drift to move around the Bay and Headland.
- Deposition occurs on the sheltered side of the Headland and a Spit begins to grow across the Bay.
- Occasionally secondary winds can blow on the coast.
- These cause the sediment of the Spit to bend inland forming a Hook.
- Spits form in bays where rivers prevent the Spit from growing fully across the whole bay.
- The area behind the Spit is protected from wind and waves. Gradually sediment builds up, vegetation begins to establish itself and forms a Salt Marsh.
Sand Dunes
Sand dunes from Steven Heath
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Coastal Sand Dunes
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Coral Reefs
Answer all questions found in the following worksheet.
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Mangrove Swamps
Mangrove Swamp Distribution
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Complete the following worksheet
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Coasts and People
Opportunities
Create a spider diagram of ways in which people use the coastal environment. Use the above images to give you ideas.
Hazards
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Make notes from the videos on how coastal erosion can be a potential hazard.
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Tropical Storms
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Create a report on Tropical storms:
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Hurricanes: A hurricane is a large low pressure system characterised by high winds and heavy rain. Hurricanes are also known as typhoons in East and South-east Asia and cyclones around the Indian Ocean. To be classified as a hurricane, winds must exceed 119km/hr (74 mph). Small low pressure systems are called tropical storms (63-118km/hr) and tropical depressions (0-62km/hr).
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Coastal Management
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Make notes from the Coastal Management PowerPoint, and then create a spider diagram outlining the different methods of coastal management. It should distinguish from Hard and Soft methods and also outline some advantages and disadvantages for each (do not just say expensive and ugly each time but be more specific!). Use can use Popplet or Examtime to do this. Have a look at the outline I have loaded for ideas of the structure.
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Create your 3d pop up beach with coastal management strategies
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Case Study: Create a report on the Holderness Coast. You will need to focus on three distinct areas:
- What opportunities are presented to people living in the area (the benefits the coast brings to them)
- What hazards are present (who is at risk)
- What is being done to manage these hazards.
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| coastal_management_holderness.pdf |
Part 1
Using the map below identify as many opportunities/reasons people have living on the coast. Focus on the town of:
- Hornsea
- Withernsea
- Easlington
- Mappleton
Part 2
Watch the following YouTube and identify factors that make this coast hazardous and also what is being done to protect the coast.
