Coastal Recession Flashcards
(19 cards)
When coastal recession is caused by erosional processes what are three factors?
Due to mineral composition, rock classification and the structure of the cliff
Erosion - What does mineral composition refer to?
How reactive the minerals are is how easily they are eroded
Calcite = reactive = easily chemically weathered
Quartz = not reactive (inert) = slower chemically weathered
Erosion - What does rock class/bedrock lithology refer to?
Sedimentary = limestone = least resistant - from from lithification
Igneous = Granite/Basalt = most resistant - form by molten rock from the mantle cools and hardens
Metamorphic = Slate/Marble = second most resistant - forms when sedimentary and igneous rocks are altered through heat and pressure, but do not melt in the process
Igneous can be intrusive or extrusive
Intrusive = within the ground, large crystals
Extrusive = Earth’s surface, small crystals
What is differential erosion and what does it lead to?
More resistant rock = slow erosion
Less resistant rock = fast erosion
Alternating types = headlands and bays
Permeable/porous rock = mass movement likely
How is vegetation important?
Binds soil
reduces wind speed
sparse in coastal environments due to lack of nutrients in salty water
100m of mangroves reduce wave height by 13-66%
What are pioneer species?
The first to grow + trap and stabilise sediment and add organic matter
What does psammosere mean?
Refers to the succession of dunes
Succession = ecosystem changes over time
Why do sand dunes form at the back of beaches?
Wind pushes them back - forms embryo dunes around obstacles
What is the process of sand dune formation?
Embryo = trapped sediment begins
Fore = Marram grass protects
Yellow = organic matter adds humus to soil
Grey = Shrubs and bushes grow
Mature = can support flora and oak trees
This is called climax vegetation
How do salt marshes form?
Estimated to reduce wave height by 80% in UK
Succession in salty water = halosere
Adapted plants = halophytic
50% lost since 1950 due to sea walls, reclamation of land, shrimp farming, tourism
Form due to
- steady supply of sediment
- shelter from strong waves
- fresh and salty water mix = flocculation
- algae bid and trap sediment
- saline levels drop and lead to other plants colonising
What human actions affects coastal recession?
Dredging = remove sediment from river or sea
Dams = trap sediment beyond dam wall = 100bn tonnes
Coastal management = sea wall + rip rap reduce erosion, groynes reduce LSD
What are the three factors affecting coastal recession?
Erosion
Sea level rise
Submergence
Can also be influenced by marine and sub-aerial processes
Permeability of rocks can lead to slumping
What is salt marsh succession?
A succession in salty water is called a halosere
The plants which are adapted to these conditions = halophytic plants
Salt marshes develop in estuarine areas because of:
- A steady supply of sediment from the river
- Shelter from strong waves
- In the estuarine environment fresh water and seawater mix
This causes flocculation where clay particles stick together
The deposited sediment is colonised by algae which:
Binds the sediment together
Increases organic matter
Traps more sediment
The sediment builds up and is covered by the tide for less and less time = other plants such as cord grass to colonise
Saline levels decrease and other plants colonise
This continues until a climax community is achieved
Coastal advancement
Depositional processes dominate
Rocky coasts
Rocky coasts form where there is more resistant geology - in the UK this is mainly in the north and west of the country
Cliffs of varying heights and steepness can be found along rocky coastlines:
Steep cliffs tend to be found in high energy environments
Cliffs with a gentler slope tend to be found in low energy environments
Erosion is more dominant than deposition
Two types of erosion may dominate along rocky coastlines:
Marine erosion - the action of waves
Sub-aerial erosion - weathering and mass movement
Coastal morphology
The shape and form of the coastline is known as coastal morphology
This is influenced by the rock type (geology) and structure
Lithology vs geology
Geology refers to the broad study of the Earth’s structure, processes, and history, encompassing everything from rocks and minerals to landforms and geological hazards.
Lithology, on the other hand, is a specific aspect of geology that focuses on the physical characteristics and composition of rocks themselves
Factors affecting rates of recession
Tides
Wind direction and fetch
Weather systems, seasons and storms
Economic and social losses
Business loss
Infrastructure damage
Reduction in house value due to the recession of cliffs
Displacement of communities
Isolation from others
Amenity value lost
Loss of livelihood
Fatalities
