2.a. Coastal landforms develop due to a variety of interconnected climatic and geomorphic processes. Flashcards
The influence of flows of energy and materials on geomorphic processes
- weathering
Physical- the breaking apart of rock -> due to changes in temperature + rainfall
- freeze-thaw (only occurs in places where temperatures drop below 0C)
- salt crystallisation
- pressure-release- erosion of overlying rock -> reveals rocks underground -> this rock fractures due to the realise of pressure
Chemical- a chemical change of the rocks composition -> causing it to wear away
- Oxidation- when minerals in the rocks react with oxygen in air + water -> iron is very vulnerable
- Carbonation- when carbon dioxide in the atmosphere mixes with rainwater -> forming a weak carbonic acid -> acid rain then dissolves carbon in calcium carbonate rocks -> limestone + chalk are very vulnerable -> whereas non-carboniferous rocks less affected
- Solution- including hydrolysis + hydration
- Hydrolysis- minerals react with water -> may make a new mineral -> this breaks up the rock internally
- Hydration- when water molecules are added to the minerals -> increasing the volume -> causing surface flaking
Biological- the breaking apart of rocks -> from living things e.g. tree roots getting bigger, animals burrowing, chemical acids released from decaying organic matter
The influence of flows of energy and materials on geomorphic processes
- mass movement
Risk of mass movement is dependant on the…
- Steepness of slope
- Degree of conhesion of material
- Amount of water in material
Water = adds weight + lubricates surface
Slumping-
material slumps down a steep slope in a rotational manner -> creating a ‘stepped’ terrace cliff profile with material at the base (scree)
Sliding-
material moves as one mass in a straight line down a steep slope
Rockfall-
large pieces of rock fall off a steep cliff face -> causing a build up of material at the base (scree)
- freeze-thaw weathering on cliff face can cause rock to disintegrate + break off into pieces
The influence of flows of energy and materials on geomorphic processes
- wave erosion, transportation and deposition
erosion – the wearing away and removal of sediment by waves
- hydraulic action
- abrasion
- solution
- attrition (this one doesn’t shape the coastline- only the sediment)
transportation – the movement of sediment along a coastline by waves
- suspension
- saltation
- traction
- solution
- longshore drift
deposition – the dropping of sediment as a result of decreased wave energy
The influence of flows of energy and materials on geomorphic processes
- fluvial erosion, transportation and deposition
erosion – water in rivers erodes the river bank -> via hydraulic action, abrasion + solution
transportation – water transports sediment -> via suspension, saltation, traction + solution
deposition – where the river meets the sea -> water looses energy -> sediment is deposited (source of sediment for coastal landscape)
sediment brought by the river -> will the be transported via LSD -> contributing to the development of depositional landforms e.g. spits
The influence of flows of energy and materials on geomorphic processes
- aeolian erosion, transportation and deposition
erosion and transportation- winds carry sediment via suspension and hits against a cliffs face via abrasion
especially in dry landscapes
deposition - where wind speed falls -> wind deposits sediment -> contributing to the development of depositional landforms e.g. dunes -> only in landscapes with on-shore winds
The formation of distinctive landforms, predominantly influenced by erosion
- headlands and bays
found at discordant coastlines -> where bands of different rock types + permeability run PERPENDICULAR to the coastline
-> differing rates of erosion (via hydraulic action, abrasion + solution) -> soft rock erodes faster (forming a bay) -> leaving harder rock jutting out (the headland)
The eroded material is then transported away by waves
The bay is sheltered by the headland -> meaning it is a low energy environment -> allowing for deposition
Wave refraction-
Water is deeper at the headland -> meaning there is less friction with the sea bed -> resulting in stronger waves -> meaning more energy is concentrated at the headland
Water is shallower in the bay -> meaning wave energy is dissipated -> resulting in more deposition -> creating beaches in the bays
The formation of distinctive landforms, predominantly influenced by erosion
- cliffs
Horizontal bedding planes -> lie horizontal to the sea -> creating a steep cliff profile
Seaward dripping strata -> produce low angle cliff profiles -> due to mass movement causing sediment to slide into the sea
a steep outcrop of hard rock
they can then develop into a wave-cut platform
The formation of distinctive landforms, predominantly influenced by erosion
- shore platforms (wave-cut platform)
area between high and low tide mark at base of cliff eroded
forming a wave-cut notch
continued undercutting weakens support for the rock above
causing it to fall under gravity (mass movement event)
process repeats
causing the cliff to retreat
forming a wave-cut platform
The formation of distinctive landforms, predominantly influenced by erosion
- geos and blow holes
Geo-
waves attacks a vertical joint or crack in a cliff -> making it bigger -> the roof looses support and will fall in -> forming a vertical gap in the cliff
Blowholes-
formed in the early stages of a geo -> waves push water up narrow inlet
or
in a cave -> constant upwards wave movement into cave can erode the headland
The formation of distinctive landforms, predominantly influenced by erosion
- caves, arches, stacks and stumps
The formation of distinctive landforms, predominantly influenced by deposition
- beaches
formed in low energy environments -> enabling deposition
more constructive waves -> stronger swash -> deposit -> net gain of sediment
Positive feedback system -> wider beaches dissipate more wave energy -> meaning more sediment deposited
Sediment is composed of either sand or shingle
Sand -> allows little percolation of water -> meaning backwash is strong -> flatter beach profile
Shingle -> more water can percolate -> meaning less water can move back -> meaning a weaker backwash -> steeper beach profile
Features that can be found-
Storm beach - when large sediments accumulate at the back of the beach -> after storm conditions
Berm - a ridge of sediment running parallel to the sea -> formed as a result of the high tide pushing sediment up -> this acts as a marker for where water at high ride reaches
Cusps - semi-circular depressions -> formed as a result of the movement of swash and backwash
Seasonal changes (summer vs winter beach profile)-
Winter -> more storms -> stronger winds + waves -> more destructive waves -> more sediment removed from beach -> flatter beach profile
Summer -> calmer conditions -> weaker winds + waves -> more constructive waves -> more sediment added onto beach -> steeper beach profile + berms build up
The formation of distinctive landforms, predominantly influenced by deposition
- spits
a deposit of sediment -> formed by longshore drift transporting sediment towards the distal end of the beach in the direction of the prevailing wind -> and depositing it where wave energy in reduced -> where there is an indentation in the coastline i.e. a rivers mouth
salt marshes often form behind
The formation of distinctive landforms, predominantly influenced by deposition
- on-shore bars and tombolos
on-shore bars-
a spit that extends across a bay + connects one headland to another -> a lagoon is formed behind this
tombolos-
a spit that extends out into the ocean + joins to an island
The formation of distinctive landforms, predominantly influenced by deposition
- salt marshes
this is a depositional landform with salt-tolerant vegetation growing out of it
only forms in sheltered environments e.g. behind spits
rivers deposit silt and clay -> creating a mudflat -> this allows pioneer species to develop -> they the die -> adding nutrients into the soil -> allowing for more plants to grow -> this continues until the climax ecosystem is reached
