Coasts Flashcards
Name the processes that happen at the coast
- Weathering
- Transportation
- Erosion
What is Mechanical weathering
The breakdown of rock at without changing it chemical composition
Process of Mechanical weathering
- Water fills a crack or joint
- Water freezes -> crack is widened (pressure)
- Repeated FREEZE-THAW-ACTION increases the size of the rock
- Block of rock falls off, loose blocks are called scree
What is Chemical weathering
The breakdown of rock by changing its chemical composition
- Warm wet conditions
Process of Chemical weathering
- Rainwater has co2 dissolved in it -> weak carbonic acid
2. Reacts with rock that contains calcium carbonate, wears away the rock
Process of Biological weathering
- Roots of vegetation grow in cracks
- Splits the rock apart
- Organic acids released speed up chemical weathering
What is mass movement
When material shifts/ moves down a slope/ surface
Sliding (mass movement)
Large chunks of rock slide down the slope QUICKLY without warning
Slumping (mass movement)
(Clay cliffs)
Clay becomes saturated, during heavy rainfall and OOZES down towards the sea
4 Processes of erosion
- Hydraulic action
- Abrasion
- Attrition
- Solution
Hydraulic action
- Water is force into cracks in the rock
- Compresses air
- Wave retreats -> air blasts out
- Rock breaks apart
Abrasion
- Eroded particles in the water SCRAPE and RUB against the rock, removing small pieces
Attrition
- Sediment collides with each other and breaks into smaller pieces.
- Their edges get rounded off
Solution
- Weak carbonic acid in seawater dissolves material from the rock, like chalk and limestone
Which waves carry erosive power
DESTRUCTIVE waves
Formation of a wave cut notch/platform
- Sea erodes the base of a cliff
- The notch increases in size -> cliff collapses, rock above is unsupported
- Collapsed material is carried by backwash
- New wave cut notch starts to form
- Repeated collapsing results in the cliff retreating
Formation of a headland and bay
- Alternating bands of hard + soft rock make up the coast line
- Destructive waves -> erode the soft rock to from bays
- More resistant rock sticks out as a headland (steep sides)
- Bay -> Constructive waves deposit + build up beaches
Formation of a cave, arch and stack
- Waves crash into the headlands + enlarge cracks (HA or ABRASION)
- Repeated erosion causes a cave
- Cave deepens until it breaks through the headland - forming an arch
- Rock supporting arch wears away - collapses
- Forming a stack
4 Processes of transportation
- Traction
- Saltation
- Suspension
- Solution
Traction
LARGE pebbles are PUSHED along the sea bed by water
Saltation
PEBBLE sized particles are BOUNCED along the sea bed by water
Suspension
SMALL particles are CARRIED along the water
Solution
SOLUBLE material dissolve in the water and are CARRIED along
Process of Long shore drift
- Waves follow the direction of the prevailing wind
1. Waves break on to the beach (swash)
2. Particles of sediment are carried with waves
3. Backwash carries material DOWN the beach, at right angles
4. Process repeats along the beach (zigzag)
What is deposition
Material carried by the sea water is DROPPED on the coast
Greater deposition than erosion -> Coast is built up
Formation of a spit
- Longshore drift occurs along the coastline
- Coastline ends -> material is deposited (cant go any further, change in depth)
- Material builds -> ridge of shingle and sand
- Strong winds -> Curve the end around
5.
Formation of a beach bar
- Constructive waves approach in the PVD
- Sediment is moved up the beach is swash
- Some is deposited, rest moves in backwash
- Some sand will be deposited in the bay between 2 headlands, rest is across forming a beach bar
- A lagoon is formed behind, where the bay was
Properties of DESTRUCTIVE waves
- Strong BACKWASH
- ERODE sand FROM the beach
- More frequent than constructive
- Sand is deposited out at sea -> causing an OFFSHORE BAR
Properties of CONSTRUCTIVE waves
- Strong SWASH
- Transports sand UP the beach
- Less frequent than destructive
- Sand is deposited as a BANK or BEACH BERM
When does deposition occur
When a wave LOOSES ENERGY and can no longer carry the sediment load
Examples of Hard engineering
- Sea wall
- Rock armour
- Groynes
Examples of soft engineering
- Beach nourishment
- Dune regeneration
- Marsh creation
- Managed retreat
HUMAN reasons of why a cliff might collapse
- Building on cliffs
- Removal of beaches
- Narrow or no beaches
PHYSICAL reasons of why a cliff might collapse
- Resistance of the rock (geomorphology)
- Saturated ground
- Weathering (biological, chemical, freeze thaw
- Stormy weather (destructive waves)
What is a sea wall with benefits and disadvantages
Wall made out of hard material; concreate, reflects waves back into the sea \+ Prevents erosion \+ Long lasting \+ Acts as a barrier - prevent flooding - Creates a strong backwash - Very expensive (£2,000 per metre) - Hard to maintain - Unattractive
What are Groynes with benefits and disadvantages
Wooden or stone fences built at right angles, trap material transported by LSD
+ Create wider beaches -> Slows waves -> protection from erosion and flooding
+ Fairly cheap
- Stop transport of sediment - increases risk of erosion along the coast
What is Rock armour with benefits and disadvantages
Boulders that are piled up along the coast
+ Absorb wave energy -> reduce erosion and flooding
+ Fairly cheap
- Need replacing often
- Not very natural
What is beach nourishment with benefits and disadvantages
Sand and shingle from elsewhere, added to beaches
+ Creates wider beaches -> slow wave energy -> reduce erosion + flooding
+ Most natural
- Constant maintenance
- Very expensive
What is Dune regeneration with benefits and disadvantages
Creating or restoring sand dunes by either nourishment, or by planting vegetation
+ Provide a barrier between land & sea
+ Wave energy is absorbed
+ Provides habitats
- Can be damaged by storms
- Restricts certain access
Reasons for sea levels rising
- Melting ice -> Increases volume of water in the sea (Antarctic sheet)
- Heating oceans -> Increased global temp -> oceans are warmer, expand -> Sea level rises
