Q2: Characteristic coastal landforms contribute to coastal landscapes

Factors affecting wave size: Fetch distance, Water depth and how it changes, Wind strength/duration

CONSTRUCTIVE WAVES: Add sediment, strong swash, weak backwash, generally found in shallow water with gently sloping beaches 

DESTRUCTIVE WAVES: Stronger backwash than swash, removing sediment off the beach, commoon when slower waves approach a steeper beach

WAVE EROSION PROCESSES: 

• Hydraulic action: Wave hits cliff, pressure on rock which loosens it. Air also compressed into cracks, then released when wave falls away, can shatter rock around crack
• Corrosion: Seawater/salt spray may react with rock minerals and dissolve them
• Abrasion: Destructive waves pick up sand/pebbles and throw them against cliff wearing it away
• Attrition: Pebbles/rock particles continually moved around by waves, colliding and eroding one another

THIS CREATES: Wave-cut notches/platforms, cliffs, caves, arches, stacks and stumps

Sediment transportation is influenced by angle of the waves, longshore drift, tides and currents: Longshore drift: Dominate wind and wave dirction determine direction of longshore drift, waves approach at angle, backwash carries same sediments back at right angles to shore due to gravity

Tides and currents: Changes in water level due to gravitational pull of moon, two high tides and two low tides a day. Difference in height between high and low tide is tidal range. High tidal range creates powerful tidal currents as tides rise and fall, important in transporting sediment 

SEDIMENT CELL CONCEPT

Erosion (source), transport (transfer) and depostion (sinks) processes operate in a linked system. Can be regarded as a closed system with little transfer from one cell to another. In theory, sediment cells will be in dynamic equilibrium. Within sediment cells there may be negative or positvie feedback

POSITIVE FEEDBACK: change balance until new equilibrium reached, e,g, storm damages sand dunes, removing sediment preventing dune stabilisation 

NEGATIVE FEEDBACK: maintains balance e.g. erosion causes rock fall which protects cliff base

Beaches: Usually low energy environments. longshore drift brings sediment, mostly by constructive waves. subariel processes of mass movement can also supply sediment.

Spits: 1) recurved spit: forms from dominant main longshore drift direction, plenty of sediment, and when there is a gap in the coastline e.g. bay, Long narrow feature made from sand or shingle, extending into sea.                                                                                                                                         2) double spit: occurs when there ae local variations in longshore drift and a large bay with strong river currents stopping them joining e.g. Poole Harbour, Dorset

Offshore bars: submerged ridges of sand, created by destructive waves eroding sand from beach and backwash deposits it offshore in bars

Barrier beaches (bars): Beach or spit extends across a bay forming a barrier beach e.g. Start Bay in Devon

Tombolos: Beach formed between a small island and the mainland.

Cuspate Foreland: triangular shaped headland, longshore drift from both directions means sediment deposited from both sides, vegetation then grows and stabilises landform.

Weathering: Gradual breakdown of rock (in situ, not moving) 

1) Mechanical: breakdown of rock due to physical processes

• Freeze thaw (water enters cracks, when it freezes it expands forcing the rock apart) 
• Salt crystallisation (waves splash on coastal rocks, water evaporates leaving salt crystals in cracks, grow and exert pressure forcing rock apart) 

2) Chemical: breakdown of rock caused by chemical reactions

• Oxidation (oxygen combines with iron minerals in rock, causing rusting making erosion easier)

3) Biological: breakdown of rock due to the presence of vegetation or living creatures

• Molluscs (live on coastal rocks to get food, boring a hole in the rock to make a home making the rock weaker) 

Mass Movement: the movement of weathered materials down slope as a result of gravity

1) Rock Fall: jointed and steep rock faces (over 40 degrees) exposed to weathering, falls to form scree or talus. This can form talus scree slopes at the base of the cliff

2) Block falls: when joints/bedding planes are roughly parallel to steep slope, water can reduce friction and cause rocks to slide over and fall 

3) Rotational slumping: common in softer materials like clay, rotational movement, vegetation usually still in tact on top of slump. Creating rotational scars in cliff. Sequence of slumps will create a terraced cliff profile

4) Flows: heavy rain and high clay content cuases earth and mud to flow over underlying bedrock