LITHOSPHERE CORE COASTLINES 1 MARINE DEPOSITION PROCESSES.

LITHOSPHERE CORE COASTLINES 2 BEACHES Beaches are a buffer zone between the waves and the coast. They usually lie between high and low tide marks, but storms can throw material up beyond high tide marks.

LITHOSPHERE CORE COASTLINES 3 The main activity of constructive waves is to deposit pebbles, sand and mud to form a beach. The sea sorts this material into different sizes according to its weight as it moves it about in the water.

LITHOSPHERE CORE COASTLINES 4 LONGSHORE DRIFT On-shore winds make waves approach at an angle ( swash), but they go back down ( backwash) at right angles to the beach. What is the result of this process? Backwash direction Low tide mark Intertidal zone High tide mark Splash zone Swash direction

LITHOSPHERE CORE COASTLINES Some help for your explanation Waves reach the beach at an angle. Waves deposit material in their swash. The prevailing wind is the direction that the wind blows most of the time. Longshore drift is the result of wave action. As the waves move up the beach they remove and deposit materials like sand and pebbles. The direction of the waves is dependent on the prevailing wind. Constructive waves remove material from the beach in their backwash.

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LITHOSPHERE CORE COASTLINES 9 Make sure that you can explain how longshore drift works and draw a labelled diagram.

LITHOSPHERE CORE COASTLINES 10 How do Sand Spits form? Longshore drift moves large amounts of material along the beach until there is a sudden change in the direction of the coastline. The sand keeps on moving in the original direction, even though there is not a coastline to follow. The sea has to be relatively shallow and sheltered allowing the accumulation of sand usually beyond a headland. Sometimes a curve develops if the on- shore wind changes direction. Spits can become permanent if the prevailing wind picks up sand and blows it inland forming sand dunes.

LITHOSPHERE CORE COASTLINES 11 Hurst Spit in Hampshire is an example that you can quote in the exam.

LITHOSPHERE CORE COASTLINES 12 On page 289 of WIDER WORLD there is a diagram to copy; fig HURST SPIT, HAMPSHIRE

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LITHOSPHERE CORE COASTLINES 14 How Do Bars and Lagoons form? A bar is a barrier of sand stretching right across a sheltered bay. It usually stretches across the bay due to the absence of any large river that might wash it away. It can cut off a lagoon to the landward side. A lagoon is a body of brackish water- part salty, and part fresh. It often supports specialised plants and animals, and is protected as a nature reserve.

LITHOSPHERE CORE COASTLINES 15 This spit will become a bar if it reaches the other side of the estuary. Can you work out the direction of longshore drift?

LITHOSPHERE CORE COASTLINES 16 If a bar links up with an off-shore island, it creates a tombolo. Chesil Beach- one of the most famous bars in the UK has a tombolo called Portland Bill. Chesil beach from Portland Bill; the shingle is 29kms long. bar tombolo

LITHOSPHERE CORE COASTLINES 17 Chesil Beach Barrier beach and tombolo which retains The Fleet (lagoon)

LITHOSPHERE CORE COASTLINES 18 ORDNANCE SURVEY MAPWORK You need to be able to recognise coastal deposition landforms from a map. To practice this skill, take a copy of the question sheet and the two O.S. maps and tackle the questions. THEY ARE NOT ALL EASY !! 9

LITHOSPHERE CORE COASTLINES 19 As you revise this topic, for each feature mentioned, look back through your textbooks and this presentation. You are looking for named examples of as many features as possible.

LITHOSPHERE CORE COASTLINES 20 You have now completed the deposition section of this unit. You should be familiar with the following terms and be able to define and use them in your answers. BEACH BAY BAR SPIT TOMBOLO HEADLAND SORTING GROYNE LONGSHORE DRIFT LAGOON SALT MARSH SHINGLE SWASH BACKWASH ON-SHORE WIND

LITHOSPHERE CORE COASTLINES 21 Assess out of 6, award up to 2 marks for grid references and/or names. Do not credit repeated features. Descriptions could include: Cliffs eg Newton Cliff (GR ). Headland eg Pwlldu Head (GR ). Caves eg Mitchin Hole Cave (GR ). Blow Holes eg Bacon Hole (GR ). Shore (wave-cut) platform (GR ). Stack eg Mumbles Head (GR ). Skerries (stack or stump) eg Rothers Sker (GR ). Bay (GR592874) – Caswell Bay