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Physical Geography

Physical Geography. Must be familiar with The sea Rivers Glaciation But only need to study one in detail.

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Physical Geography

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  1. Physical Geography • Must be familiar with • The sea • Rivers • Glaciation • But only need to study one in detail

  2. Wave creation – The wind blowing across the surface of the sea creates waves. The ability of waves to shape the coast is influenced by the strength of the wind and the length of time it blows.The size of the wave depends on the FETCH, Which is the distance a wave has travelled before it reaches the land.Large fetches = BIG WAVES, because the wind has had longer to blow over the surface of the sea, creating bigger swells, e.g. The West Coast of Ireland

  3. Why are waves generally larger in the south west? Wave energy depends on the fetch, the strength of the wind and the length of time over which the wind has blown. fetch = the distance over which the wind has blown Look at an atlas or a wall map to find out the largest fetch around the British Isles.

  4. Swash and backwash Backwash Swash

  5. Waves – Swash & Backwash • Swash – As the wave reaches the shore it breaks. The white foamy water that flows up the beach is called the Swash. • Backwash – When the water runs out of speed it stops and it flows back down the beach into the sea. This is called the backwash.

  6. Constructive waves • They have a strong Swash which transports and deposits material on the beach. • They have a weak Backwash which does not carry much material back to the sea. • As a result they construct/add material to the beach.

  7. Constructive Waves

  8. Destructive waves • They have a weak Swash. • They have a very strong Backwash which wears away and carries away material form the beach. • Therefore, there is a lot of erosion and they destroy/destruct the coastline.

  9. Destructive Waves

  10. Sea erosion Is the breaking down of coastlines by the force of waves

  11. Sea Erosion • Sea erosion is caused by Destructive waves. They erode the coast in 4 ways. • Hydraulic Action • Air Compression • Abrasion • Attrition

  12. How waves erode • Hydraulic action is the power of the water itself • Compressed air is where air gets trapped in cracks by waves. The increase in pressure shatters the rock • Abrasion is when erosion occurs because rocks are slammed against the coast • Attrition is when the stones carried by the waves are themselves worn down

  13. Landforms of Sea Erosion • Like rivers, the sea creates many features or landforms as a result of erosion. These include, • Cliffs • Bays and Headlands • Sea caves, sea arch, sea stack, sea stump • Blowhole

  14. For a landform, you must • Name it • Example • Describe it • How was it formed • Diagram showing formation

  15. Bays and Headlands

  16. Bays and Headlands • A bay is wide deep opening into the coastline. • A headland is a piece of land jutting out into the sea. • Bays and headlands form when there are different types of rocks occur along the coastline. • The softer rocks are eroded quickly creating a bay. • The harder rocks are eroded slowly and so they stick out into the sea • E.g. Dublin Bay & Howth Head

  17. A cliff (2) Ex. Cliffs of Moher or Downpatrick head co. Mayo (2)

  18. Description • A cliff is a high rock face that slopes steeply up from the sea shore (2) • Depending on rock composition the cliff can retreat at a rate of up to 1m per year. (2)

  19. Formation • Often coastlines are made up of hard and soft rocks beside each other. The soft rock is eroded more easily than the hard and so bays and headlands are formed (differential erosion) (2M) • Wave refraction (when the waves bend due to the depth of sea level, book pg 166) means wave energy is greatest at headlands and cliffs begin to form. (2M)

  20. Formation • Destructive waves erode a notch at the base of a headland (2M) • The notch deepens by the processes of Hydraulic action, compressed air & abrasion (explain) (6M)

  21. The notch becomes so deep that the rock above collapses forming a cliff (2M) • The fallen debris lies at the bottom of the cliff, protecting it from further erosion. Gradually the hydraulic force of the sea removes this debris depositing it on the sea bed some distance out to sea. This accumulation of debris is called a wave built terrace. (2M) • Overtime, the repeated collapse of the rock at the cliff face causes it to retreat inland. Eventually the force of the sea is unable to erode a notch this far inland and mass movement, such as slumping, takes over as the primary cause of cliff formation. • As the cliff retreats a wave cut platform (SLOPY ROCKY LANDFORM LEFT BEHIND AS CLIFF RETREATS- EXPOSED AT LOW TIDE) is formed at the cliff base. (2M)

  22. The structure of the rock plays an important part in determining the type of cliff that is formed. (vertical or sloping) • Cliffs made from unjointed rock such as granite or schist are harder to erode and form more gently sloping cliffs, e.g. Slieve in Donegal. (2M) • Soft coastlines made of glacial till are the least resistant to erosive power of the sea. Every tide can wash soil from the base of these cliffs and heavy rainfall may cause slumping, e.g., Killiney in County Dublin. (2M)

  23. Homework 2008, 2007, 2006, 2005 Examine with the aid of a labelled diagram or diagrams, the processes that have led to the formation of any one irish landform of your choice.

  24. Caves, Arches, Stacks & Blowholes

  25. Sea caves Form when waves erode a crack or weakness in a headland

  26. Sea arch • Forms when two caves meet or when one cave burrows right through a headland.

  27. Sea stack • Formed when a sea arch collapses

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