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HOW ARE COASTAL LANDFORMS DEVELOPED - Coggle Diagram
HOW ARE COASTAL LANDFORMS DEVELOPED
erosional landforms
WAVE CUT PLATFORMS
waves undercut cliffs creating a notch, the cliff collapses and retreats
horizontally bedded
seaward dipping- undercut causes sliding towards the sea
landward dipping- profile is lowered
HEADLANDS AND BAYS
found on discordant coastlines, resistant rock isn't eroded (headland) weak rock is eroded in wards (bay
GEOS AND BLOWHOLES
geo-narrow bay/inlet formed by eroded faults and joints, cave is formed then roof collapses
blowhole- formed when only part of the roof collapses creating a vertical shaft where water is forced out from during storms
CRACK, CAVE, ARCH, STACK, STUMP
crack is eroded by hydraulic action into a cave until it reaches through into an arch where the roof eventually collapses, separating the stack which is slowly eroded until it is a short stump
depositional landforms
SPIT
when longshore drift drags material beyond the mainland, and it begins to curve round when wind changes direction
BEACHES
deposited sand
90% fluvial deposits
5% cliffs
5% offshore
sand is compact and impermeable- deposited easily
shingle allows more percolation and creates steeper beaches
beach features
cusps- temporary semi-circular depressions formed by waves reaching the same point and the backwash and swash are equal in strength.
ripples, berms, cusps, runnel, ridges
TOMBOLOS
spits that connect mainland to offshore islands e.g., chesil beach 7m (sand) to 13m (shingle) west to east, material was already there due to flandrian transgression and been moved by longshore drift.
Flandrian Transgression- sea level rise 9m over 1000 years during the upper Pleistocene period (17,000-6000bp). progressive decline in the rate of sea level rise during the Holocene (6000bp- present)
BARS
when spits close a bay forming a lagoon behind e.g., Slapton sands
SALT MARSH
the area behind a spit, shallow, stagnant salt water. Low energy, lots of vegetation but low biodiversity, saline and turbid rushes.
DELTAS
The Nile delta- low energy coastline
Physical factors
Hot and dry climate in Egypt so rock is weak and easily eroded
low energy water and low wind short fetch of 750km
uneven coastline
Weak rock composition, easy erosion, transportation and deposition
How are the landforms interrelated
Foreshore plain : elongated ridges parallel to shoreline. Lagoons, salt marshes, and alluvial deposits in the depressions between them
Frontal plain: south of foreshore plain- scattered eroded limestone outcrops and clay deposits
sandy zone: composed of different sand formations like sheets, dunes and hammocks
alluvial deposits at the Aswan are 4m but 9.6m in Cairo
nearshore underwater bars that are crescentic in the in the west and parallel in the east
How has the landscape changed over time
Before the 1964 construction of the Aswan Dam the Nile would flood and cover the delta each year in a thick layer of silty mud
northwesterly winds over the med for most of the year, moving the water eastward
surface velocity changes throughout the year
summer: 9.26-13.5 cm/s
autumn/winter: 4.46-23.14cm/s
spring: 8.4cm/s
the dam reduced sediment accretion from 120million tonnes a year to to barely traceable amounts but caused a faster retreat of the coastline - an imbalance between acting erosion and accretion.
Rising sea levels have caused higher erosion rates
Flanborough head- high energy coastline
Physical factors
Cold/wet climate, strong winds North York moors are 400m above sea level
mainly sandstone/limestone formed during the Jurassic period
Flanborough head is a chalk headline topped with deposit from glaciers during the Devensian glacial period.
How are the landforms interrelated
Dominant waves are from the north/northwest and have a fetch of 1500km so have the highest energy
the stretch between Saltburn and Flanborough is a subcell of cell 1/11
sediment in 1D has come from the nearshore area driven onshore by sea level rise, cliff erosion and deposition from the river esk
Shore platforms (cliffs are retreating) are horizontally bedded with a gentle slope
Flanborough 30-40m high chalk cliffs
Saltburn- steeper cliffs
How has the landscaped changed over time
2010-2011 wave height often exceeded 4m
most exposed areas have highest input of wave energy but variations in rock resistance so erosion rates differ
clay and shale erode 0.8m a year
sandstone and limestone 0.1m a year
2008-2011 net increase in beach sediment of 9245m3 at saltburn
landforms formed within the last 6000 years of interglacial periods
calm waters deposit sediment at estuaries, splitting it up and making it longer as the distributaries stick out, they began forming around 7000 years ago.
structure- alluvial valley, levee, upper plain, lower plain, submerged plain, front, crevasse splays (branches)
types of deltas- birds foot, arcuate delta, cuspate delta
flows
WEATHERING
mechanical
freeze-thaw- water enters cracks/pores and freezes and expands putting pressure on the space until it splits
pressure release- expansion and fracture (pseudo bedding planes) of underlying rocks after the removal of overlying rocks (dilation).
crystallisation- salt solution enters pores and crystalises, expanding and applying pressure until it splits or disintegrates
thermal expansion- repeated heated and cooling of rock (expansion and retraction) causes layers to flake off
chemical
oxidation- rock minerals react with air and water and become soluble, destroying original structure
solution- salt minerals in rock dissolve in water
hydration- water expands rock and it begins to flake off
hydrolysis- reaction between rock and water producing secondary materials e.g silicates+ water- clay
Van't Hoffs law- a 10degree increase in temperature leads to a 2.5x increase in the rate of reaction
carbonation- dissolved c02 in rain created a weak carbonic acid which reacts with CaC02 in limestone making it soluble
biological
organic acids- animal and plant decomposition makes soil acidic which weathers rock (chelation)
tree roots- roots grow into cracks in rocks, applying pressure causing it to break.
MASS MOVEMENT
linear slides-movement along a straight plane due to underlying wave action
rotational slide- weak rocks become heavier when wet creating a downward force. water can permeate sand but not clay
rockfall- rocks become detached from cliffs because of weathering and fall
mud slide- saturated soil becomes heavy and flows down a slope
WAVES
erosion-abrasion, attrition, solution, pounding, hydraulic action
transportation- traction, solution, suspension, saltation
deposition- reduction in velocity, swash
wave refraction- waves approaching discordant coastlines slow down due to friction and shallow water. the wave crest in deeper water by the bay isn't slowed down, the wave refracts round the headland and the orthogonal waves converge. wave energy is concentrated around the headland but dissipates at the bay
RIVERS
transportation- traction, solution, suspension, saltation
deposition- reduction in velocity in the lower course
erosion- abrasion attrition, solution, pounding, hydraulic action
WIND
deposition- surface friction reduces wind speed
transportation- surface creep, deflation, saltation, suspension (0.05-0.14mm). material can be carried at velocities as low as 20km/h
erosion- velocity increases erosional force of the wind, dry particles are easier to pick up. attrition and abrasion. particles can be carried for greater distances by wind and there is no water to prevent collision. abrasion isnt effective higher than 1m