Coasts Flashcards
Low-energy vs high-energy coast
Low:
•constructive waves
•longshore drift, deposition
•spit, tombolo, beach bar, salt marsh, beach
•east coast
•Anglian coast
High:
•destructive
•erosion - hydraulic action, abrasion, attrition, solution
•headland, bay, cave, arch, stack, stump, wave cut platform + notch
•west coast
•Atlantic coast
The coastal system
Inputs -> processes -> outputs
Define dynamic equilibrium
Moving balance
If we alter the coast it will shift back to maintain its system
Processes that affect contrasting coastlines
•geology (rock type):
-Igneous - hardest
-Metamorphic - changed - heat - pressure - mostly very hard
-Sedimentary - young are very weak, old are quite hard
•level of energy:
-wave caused by wind
-open ocean, long fetch - lots of energy
-enclosed seas, short fetch - lower energy
•balance between erosion + deposition
•changes in sea level - emergence & submergence:
-emergence = growing/getting bigger
-submergence = sinking
-10000 years ago - ice age, covered half UK, crustal loading - ice pushed Scotland down but dynamic equilibrium means south England rose (emergent) so Scotland is now emerging + England is now submerging = isostatic rebound
Littoral zone
Coast -> backshore -> foreshore -> nearshore -> offshore
Explain spring tide
An extra high tide due to the alignment of the earth, moon and sun creating an extra gravitational pull on the tidal bulge
Define sediment cell
Length of coastline + nearshore area within which the movement of coarse sediment is largely self-contained
Explain the three different coastlines
•cliffed coast: short littoral zone -> cliff to sea -> lack of beach
•sandy coastline: full range of littoral zone - coast, backshore, foreshore, nearshore, offshore
•estuarine coastline: mouth of rivers, mud flats, salt marsh -> long transition from land to sea -> lots of deposition
Field sketch
•outline drawing highlighting the important geographical points
•annotated
•key terms
•not coloured
•label features + processes
•doesn’t include items of general interest
Discordant vs concordant coastlines
Discordant: hydraulic action, abrasion, attrition, solution erode coast. Soft rock e.g. young sedimentary erode quickest = bay. Harder rock e.g. old sedimentary erode slower = headland. Coastline perpendicular to sea
Concordant: hard rock -> igneous, metamorphic or old sedimentary. Erode at same rate so fairly straight coast. Parts may erode with soft rock behind + form bays. Coastline parallel to sea. If water gets behind hard rock could lead to strips of land with ocean behind.
Explain wave refraction
Waves reorientated as they approach coast. Frictional drag exerted by sea floor turns wave to break parallel to shore
Explain tidal currents
Incoming + outgoing tides produce currents in opposite directions but one direction is stronger so causes one-way transport of sediment
Explain weathering
Breakdown of rock by chemical, mechanical or biological agents - doesn’t involve movement
•chemical - carbonation, hydrolysis, oxidation
•mechanical - freeze-thaw, salt crystallisation
•biological - plant roots, rock boring
Mandala grid
Geological factors affecting the shape of the coastline
•horizontal dip - vertical profile with notches reflecting strata that are more easily eroded
•Seaward dip, high angle - Sloping, low angle profile with one rock layer facing the sea; vulnerable to rock slides down the dip slope
•Seaward dip, low angle - Profile may exceed 90° producing areas of overhanging rock; very vulnerable to rock falls
•Landward dip - Steep profiles of 70-80° producing a very stable cliff with reduced rock falls
Define strata
Layers of rock
Define bedding planes (horizontal cracks)
These are natural breaks in the strata, caused by gaps in time during periods of rock formation
Define joints (vertical cracks)
These are fractures, caused either by contraction as sediments dry out, or by earth movements during uplift
Define folds
Formed by pressure during tectonic activity, which makes rocks buckle and crumble (e.g. the Lulworth Crumple)
Define faults
Formed when the stress or pressure to which a rock is subjected, exceeds its internal strength (causing it to fracture). The faults then slip or move along fault planes
Define dip
This refers to the angle at which rock strata lie (horizontally, vertically, dipping towards the sea, or dipping inland)
Define relief
Height and slope of land
Define morphology
Shape
Define wave period
Time taken for two crests to pass a given point
Equation for wavelength
Wave length = velocity x wave period
Explain the two types of waves
•constructive - strong swash + weak backwash - deposition
•destructive - weak swash + strong backwash - erosion
Ways sediment is transported in water
Traction - rolling
Saltation - skip
Suspension - flow of water
Define gravity settling
Sinking
Define flocculation
Particles have electrical charge and when big enough they will deposit
Define sediment cell
Area of coastline where erosion, transport + deposition happens
Define sources
Where the material comes from
Define transfer zones
Transport (longshore drift)
Define sinks
Store
Explain sediment cells
•11 in the UK - sediment tends to stay in the same cell
•’theory’ - sediment can move to another cell in extreme cases - storms
Define sub-aerial
Below air e.g. weathering and mass movement
Acts on cliff face, whereas marine processes act on cliff foot
Define and explain Mass movement
Any large-scale movement of earths surface that aren’t accompanied by a moving agent (sub-aerial + marine processes)
•flow
•slide
•falls
•slumps
•avalanches
Define weathering
The breakdown of rocks by 3 different processes (no movement is involved)
The different types of weathering
Biological:
•plant/tree roots expanding
•rock detached
•seaweed acids
Mechanical:
•salt crystallisation
•pressure release
•frost shattering
•exfoliation
Chemical:
•oxidation
•hydration
•hydrolysis
•carbonation
•solution
•acid rain
Block-fall landslide case study
Burton Bradstock cliff collapse
Define isostatic change
When the land rises or falls, relative to the sea
Define eustatic change
When the sea level itself rises or falls
Define accretion
Accumulation of sand or land mass over time along coastal regions
Define post-glacial isostatic adjustment
Ice sheets retreat - land begins to rise
Define ria
Sheltered winding inlets with irregular shorelines
Define barrier islands
Deposit of sand parallel to coast
Two case studies suffering from sea level rise
•Kiribati
•south/south east of UK
Isostatic v eustatic
Isostatic:
Land rises + falls, crustal loading
Eustatic:
Global water rise, melting ice sheets
Coastline protected from erosion by the stabilising influence of plants
•coastal sand dunes
•coastal salt marshes
•coastal mangrove swamps
Vegetation stabilises sediment:
•roots of plants bind sediment together - harder to erode
•plants provide protective layer, surface of sediment isn’t directly exposed to moving water
•decreased wind speed at surface due to friction with vegetation - decreased wind erosion
Plants that grow in coastal environments:
•halophytes can tolerate salt water
•xerophytes can tolerate very dry conditions
Define succession
The changing structure of a plant community over time as an area of initially bare sediment is colonised by plants
Define pioneer species
Specialised plants that grow in bare sand or mud
Define seral stage
Each step in plant succession
Define climatic climax community
A new ecosystem area
Define psammosere
A sand dune ecosystem
Define halosere
A salt marsh ecosystem
Embryo dune pioneer plants:
•stabilise the mobile sand with their root systems
•reduce wind speed at surface, allowing more deposition
•add dead organic matter to sand, begin soil formation
Define fore dune
New plant species colonise embryo dunes
Define grey dune area
Once an embryo dune but due to plant colonisation + succession, the dunes have grown upwards + out to sea
Define dune slack
Low areas within dune systems
Marram grass
Tough, long, flexible waxy leaves - can deal with ‘sand blast’ in strong winds, limit water loss through transpiration
3m roots - reach water
Tolerate 60 degree temp
Grow up to 1m a year - keep up with deposition
Why are Estuaries ideal for salt marshes
Sheltered from strong waves - deposition
Salt marsh succession
•Grow in mud - bind it together
•roots stabilise mud
•vegetation, salt marsh height increases
•rarely submerged
•developed soil profile + only submerged once or twice a year
Case study for rapid coastal erosion
Holderness
Name for increased erosion due to groynes
Terminal groyne syndrome
Define dredging
Digging
Define river discharge
Flow of a river (cumecs)
Case study for DAM’s
Alexandria
Define adaptation
Learning to live with the problem
Define mitigation
Stopping the problem
Define reclamation
Someone drains the land + reclaims it
Define environmental refugees
Have to move due to environment
Define tropical cyclone
Warm weather low pressure systems, air rises, cools, condenses + precipitation, pull air from sides, spin of earth causes wind to rotate around the low pressure - coriolis force
Where does a depression happen
Mid latitudes - 40-60 degrees N/S of equator
Where does a depression happen
Mid latitudes - 40-60 degrees N/S of equator
Define storm surge
Higher than average waves caused by strong winds pushing water to land, air rises and pulls surface water up
Case study for flooding and low level of development
Bangladesh
Define non-governmental organisations (NGO)
Charity
Define fisheries
Huge areas where people farm fish
Mega projects
Define return period
Time before you get your money back
2 case studies of coastal flooding
•Australia
•Philippines
Define internally displaced people
Within a country
Define environmental refugees
Forced to move by natural causes
Case study for coastal community at risk due to climate change
Maldives
Coastal management
•groynes
•sea walls
•rip-rap
•revetments
•offshore breakwaters
•gabions
•beach nourishment
•cliff regrading
•cliff drainage
•dune stabilisation
•managed retreat
Environmental impact assessment
Cost-benefit analysis
Compare costs + benefits before coastal management project to decide if it should go ahead
Tangible + intangible costs/benefits
Define coastal realignment
Managed retreat
Two case studies for coastal management
•Namibia
•Essex, UK
Sand dune case study
Morfa Bychan, North Wales
•nature reserve
•recreation
•holidays
•tourism
•golf course
Coastal dune development case study
Morfa Bychan
Coastal landscapes and change case study
Criccieth
Define ICZM
Integrated coastal zone management
Coastal action options
Do nothing
Managed realignment
Hold the line
Move seaward
Limited intervention
Case study for coastal management
Holderness coastline
Case study for conflicts over coastal management strategies
Happisburgh
Use of the coast in Bangladesh
•ship breakering
•expanding due to globalisation
•ship life span = 25-30 years
•environmental standards low (laws)
•use flat beaches to ground ships, then cut it up
•dangerous work - toxic
•aim to recycle the metal
•15 deaths per year
Case study for coastal management in countries at different levels of development
Chattogram in Bangladesh
