Coasts, Last Minute Flashcards
(24 cards)
What are the 4 types of transportation?
- Traction - large heavy material is dragged along the sea floor
- Saltation - smaller sediment bounces along the sea / river floor.
- Suspension - lighter material carried through the river flow.
- Solution - Soluble materials (like calcium carbonate from limestone or chalk) are chemically dissolved by acidic seawater and carried through the flow.
What is the main factor affecting the direction of sediment transport.
The direction that the waves are coming from is the main factor affecting the direction of sediment transport.
Why do waves lose energy?
- The wind slows or changes direction
- The wave experiences friction, usually with the sea floor as the depth decreases
- When the coastline changes direction such as at an estuary or headland
Where do Depositional Landforms occur?
Depositional landforms occur at low energy coastlines when the waves do not have enough energy to carry a large sediment load
Describe High vs Low Energy Coastlines sediment landscape
High energy coastlines deposit large rocks and shingle but generally maintain enough energy to carry smaller sediment particles
- This is why these types of coastlines tend to have rocky beaches, such as Brighton on the south coast of England
Low energy coastlines deposit smaller sediment due to low wave velocity, creating sandy beaches
Where is the most common depositional landform
The most common depositional landform is a beach
- Beaches build up due to constructive waves
- They form in sheltered areas such as bays
- Beach formation is more common in summer when there are fewer destructive waves
Explain drift aligned beaches be drift aligned?
Beaches can be drift-aligned or swash-aligned
- Drift-aligned beaches form where longshore drift moves the sediment along the beach as waves approach at an oblique angle
This will often culminate in a spit where the coastline changes direction
Explain swash aligned beaches?
Beaches can be drift-aligned or swash-aligned
- Swash-aligned beaches form where the energy is low
The waves are more parallel to the shore in swash aligned environments so there is little horizontal or lateral movement of sediment
What is fetch?
Fetch is the uninterrupted distance over water that the wind blows in a single direction, generating waves.
- Longer fetch = more time and space for wind to transfer energy into the sea = larger and more powerful waves.
- Shorter fetch = less energy transferred = smaller, lower energy waves (often constructive).
barrier beach vs bar?
The main difference between a bar and a barrier island is that a bar joins two headlands, whereas a barrier island is open at one or both ends
Define weathering?
Weathering is the breakdown of rock in its place of origin (in situ)
3 core types of weathering?
- **Mechanical (Physical) ** - When rocks break down, with no chemical changes
- Biological - Rock breaks down due to organic activity
- Chemical - Rock breaks down due to a chemical reaction - rock changes
Explain mechanical weathering in depth?
- Freeze Thaw - places where night temps reach below 0 - water from rainfall collects in a crack of a rock. When it freezes, it expands wideining the crack and then melts. - this repeats until rock breaks apart.
- Salt crystallisation - Salt crystallisation occurs because salt crystals are bigger than water molecules and DO NOT evaporate away when the sun evaporates the water. This exerts pressure on the rock, causing the rock to break down.
- Exfoliation/onion skin weathering - This happens in hot climates. When rocks warm up during the day the rock expands. At night the rock cools and contracts. Over time this causes very thin layers of rock to flake off.
Explain biological weathering in detail
- Plant roots - grow and enter cracks in the rock under soil, as the plant and roots grow, the roots put strain on the cracks, causing them to get larger. Rock breaks away.
- Nesting birds and small burrowing animals like rabbits can also cause rock to breakdown through biological weathering
Explain the 3 chemical weathering techniques in depth?
Carbonation
* Process: Rainwater (which is slightly acidic due to dissolved COâ‚‚) reacts with calcium carbonate in rocks like limestone or chalk.
- Effect: The rock slowly dissolves, widening joints and forming features like limestone pavements or karst landscapes.
Oxidation
Process: Iron-rich rocks (e.g. sandstone with iron minerals) react with oxygen in air or water.
Effect: Forms iron oxide (rust), which weakens the rock and causes it to crumble or break apart.
Solution
* Process: Soluble minerals like halite (rock salt) or gypsum are dissolved by freshwater or seawater.
- Effect: Gradual removal of material, contributing to rock breakdown in coastal and arid environments.
Define mass movement and what the type of movements are
The downhill movement of material under the influence of gravity
- Soil Creep
- Flow
- Slide
- Fall
- Slump
What are the factors that affect the type of mass movement?
- Angle of slope (the steeper the slope the faster the movement)
- Nature of regolith (weathered material)
- Amount and type of vegetation
- Water
- Type and structure of rock
- Human activity
- Climate
Explain soil creep
Common in humid climes with the movement of less than 1cm per year
Soil expands when it freezes, gets wet or is heated up in the sun
As the soil expands, it lifts at right angles to the slope
When the soil shrinks, it falls straight back down
Soil creep takes a long time because the soil moves only a millimetre to a few centimetres at a time
Essentially just the slow movement of soil from its freezing and cooling over time.
Explain slumping
- Usually found on weaker rock types (i.e. clay), that become saturated and heavy.
- This is common at the coast and is also known as rotational slip
- It involves a large area of land moving down the slope in one piece
- Because of the way it slumps, it leaves behind a curved indented surface
Enhanced by saturation / water / rainfall or even human activity.
What are the mass movement landforms?
- Rotational scars
- Talus scree slopes
- Terraced cliff profiles
What are sub ariel processes?
Sub-aerial processes = processes that attack the land from the air (i.e. above the waterline), weakening the rock and making it more vulnerable to erosion.
It is MASS MOVEMENT AND WEATHERING
4 types of EROSION
Abrasion - sediment and stones are picked up by the waves and wear away at the cliff/headland
Hydraulic action - this is the shear force of the waves forcing air at high pressure into cracks in the cliff over time this weakens the rock and causes the joint to widen
Corrosion - weak acids in seawater dissolve the rock particles
Attrition - as rocks are moved around by the water they knock into each other gradually becoming smaller and rounder
Alternative explanation of Hydrualic action?
Hydraulic action is the mechanical erosion caused by the force of waves crashing against a rock surface.
When waves hit the cliff, air is forced into cracks and joints at high pressure.
As the wave retreats, the compressed air rapidly expands — this sudden release can cause mini explosions inside the rock.
Over time, this pressure cycle causes the rock to weaken, fracture, and eventually break apart.
