Coasts Flashcards
Concordant
Alternating bands of rock parallel with the waves
Discordant
Alternating bands of rock perpendicular with the waves
Isostatic change
Localised rise or fall in land
Eustatic change
Global rise or fall in sea level
Sediment cell
Region of shoreline that encompasses sediment movement
SMP
Strategies to manage flood/erosion risk
ICZM
Overviews the strategies put in place to protect coasts, accounting for all parties of interest.
Rock types and examples
Metamorphic - Slates & marbles
Sedimentary - Limestone & sandstone
Igneous - Granite & basalt
Unconsolidated - Sand & clay
Factors for dune creation
Abundant sediment supply
Macro-tidal range
Predominant onshore wind
Vegetation
Factors affecting waves
Fetch
Power of wind
Water depth
Weathering
Decomposition through direct contact with the atmosphere in-situ
Exfoliation
Expands when hot and contracts when cold so layers peel away
Freeze thaw
Cracks fill with water, which expands when frozen, this repeats causing pieces to break off
Salt crystallisation
Salt water evaporates, leaving salt crystals which grow and widen cracks, breaking off rock
Biological weathering
Plant roots clump soil together and loosen the ground
Chemical weathering
Rock is weakened through hydrolysis, carbonation or oxidation. (usually acid rain)
Topple (mass movement)
Forward rotation of rock on vertical lithology , where weaknesses exist at bedding planes.
Rotational slumping
Cliffs made of sands or clay become saturated and slide down with a rotational movement, leaving behind a terraced profile and rotational scar
Rockfall
Rapid movement on cliffs exceeding 40 degrees caused by weathering. Leaves a talus slope at the foot (debris)
Earthflow
Steeper slopes that have become saturated and masses of earth slides down the slope
Flocculation
Clay particles suspended in water gain an electrostatic charge from the salt, so clump together and sink.
Sediment sources
Rivers
Beaches
Cliff erosion
Attrition of boulders
Sediment stores
Offshore bars
Beaches
Sediment outputs
Offshore
Humans & animals
Ria
Flooded river valley, dentritic shape
Fjord
Flooded glacial valley, not dentritic, far deeper than ria
SMP examples
Do nothing
Managed realignment
Hold the line
Advance the line
Limited intervention
Beach nourishment
Adding sediment to beach
+Natural, supports tourism
-Storms can destroy, needs to be repeated
Groynes
Walls that stop LSD
+Not as expensive as others, supports tourism
-£1000 per m, ugly, disrupts sediment cells
Revetments
Sloped walls in front of backshore
+Effective, LSD continues
-Very expensive(£1500/m), less accessible
Sea wall
Wall/pier that reflects waves
+Very effective and lasts, supports tourism
-£5000/m, interrupts cells by stopping erosion and deposition
Rock armour
Boulders that dissipate waves
+Long lasting, effective
-Expensive if shipped from abroad, may not fully prevent erosion
Gabions
Pebbles in wire basket
+Relatively cheap and easy, can also prevent mass movement
-Not very effective against high energy, frequent repair needed
Formation of tombolo
Waves are refracted by an island so have low energy and deposit sediment, connecting it to the land.
Formation of cuspate forelands
Two spits either side of a triangular headland meet.
Dune succession
Embryo - Sand piled up by an object
Yellow - Vegetation grows as the dune gets bigger (Marram grass)
Grey - Moisture & nutrients from plant death create soil, so more plants can grow
Dune slack - Water table rises to the surface or sea water trapped in between
Heath & woodland - Trees can now grow
Wave quarrying
When air is trapped and compressed against a cliff, causing rock fragments to break off
Negative feedback loop eg
Beach is eroded by storm waves, creating an offshore bar. This then dissipates wave energy and is eroded, eventually returning to normal conditions.
Clastic vs Crystalline
Clastic - Sandstone, limestone etc
Crystalline - Igneous/metamorphic
Short-term sea level change
-Tide
-Wind strength/direction
-Atmospheric pressure (lower pressure = higher sea level)
