ENQ2: How do characteristic coastal landforms contribute to coastal landscapes
2.4 Marine Erosion Creates Distinctive coastal landforms and contributes to coastal landscapes.
2B.4 a Different wave types (constructive/ destructive) influence 2B.4b The importance of erosion processes (hydraulic action, corrosion,
beach morphology and beach sediment profiles, which vary at a abrasion, attrition) and how they are influenced by wave type, size and
variety of temporal scales from short term (daily) through to longer lithology.
periods.
What is 1. When a wave crashes against the cliff face, the air
hydraulic trapped in cracks is compressed by the force of
Constructive waves: action? the wave.
2. Pressure builds up and forces cracks open which
means more air is trapped.
Features - Low energy – dissipates over wide area so 3. This means that a greater force is experienced in
strong backwash. the next cycle of compression.
- Long wave length. 4. This process loosens blocks of rocks that break
- Short height. away from cliff face.
- Low frequency between 6 and 8 waves per
minute. What is 1. Sediment is picked up by breaking waves (usually
- swash is strong whereas backwash is weak so abrasion? during storm) and is thrown against the cliff face.
deposition is greater than erosion. 2. This repeated motion eventually wears away the
Beach - sand and fine material deposited and left cliff.
morphology/sedim behind.
ent profiles - Builds up each other time making it wider and What is 1. Sediment is moved around by waves.
flatter. attrition? 2. Collision between particles causes parts of rock to
- Creates features like berms – ridges of break away.
deposited sediment – and a sandy surface. 3. Becomes smaller and more rounded over time.
- Since backwash is weak, sediment stays at
beach which grows. What is 1. Carbonate rocks (limestones) are vulnerable to
corrosion? solution by rainwater.
2. Dissolve rocks minerals which are carried away by
wave in solution.
Destructive waves: 3. They are vulnerable to erosion by railway and sea
spray.
Features - High energy.
- Short wavelength. Factors affecting erosion:
- Tall breakers that have high downward Factor Affect on erosion
force and strong backwash. Wave type - Destructive waves -> higher downward force, high
- Encouraged by short steep nearshore zone energy environments, stronger backwash = greater
quickly dropping into deeper water so little erosion (HA + abrasion).
energy lost through friction. - Constructive waves ->low energy, strong swash =
- Frequency – 13 to 15 waves per minute. more deposition than erosion, limited HA.
Wave size - Larger waves = more energy = more erosion.
-
- Wave energy increases with wind speech, wind
Beach - Backwash stronger than swash which pulls duration + fetch.
morphology/sediment sand and finer materials away from each, - Bigger waves have greater force to break rocks
profiles dragging out to sea, eroded. apart and hurl larger sediment at cliff face.
- Creates offshore bars where material Lithology - Granite/basalt -> very hard, erode slowly, resistant
deposited. to all processes.
- Particles left behind on each are pebbles or - Sandstone/limestone -> moderate resistance, erode
shingle which creates narrow, steep beach moderately – limestone is vulnerable to erosion.
profile. - Clay/shale -> soft resistance, erode rapidly, easily
broken by HA and saturated by water.
Evaluate the variety of temporal elements involved and their importance in - Chalk -> soft and chemically weak so vulnerable to
shaping out coasts solution and HA.
Short - 2 high tides (6am+ 630pm) and 2 low tides (12:15pm and - Jointe/fractured porous rocks erode faster as water
term – 12:45am). can penetrate + air compression.
daily/tida - High tide -> waves reach further up each affecting
l backshore. Erode berms or cut small notches in upper CASE STUDY – comparing geology + fetch
beach. In storms high tide + destructive waves = dune 2 natural processes causing coastal erosion:
erosion. Finer sediment may be pushed further inland and - Waves from direction of prevailing wind = longest wind direction and
larger sediment may be deposited at wash zone during
thus increase energy, encouraging high energy coastline.
rougher conditions.
- Fetch = distance the wind has blown. Greater distance, more energy
- Low tide -> wave breaks lower on beach near
and thus more powerful wave.
foreshore. Exposes larger surface area to wave energy.
Cusps, pools created in exposed sand/shingle. Find sand
often found in shallow, low tide areas. South West UK:
Daily weather patterns: - Large fetch of 2-6M.
- Calm weather = constructive waves dominate – more - Due to prevailing winds across Atlantic from Gulf of Mexico.
deposition – sand ridges. - Thus expect high levels of erosion.
- Stormy weather = destructive waves – sudden erosion, - High energy coastline
steepen beach, create storm ridges. - BUT SW geology = igneous rocks such as granite = Lansden.
Neap/Spring Tides 28 day cycle: - Granite = interlocking spurs of crystals, high resistance.
- Spring Tides: - Relatively low levels of erosion.
o During full moon and new moon.
o Sun + moon align, increasing gravitational pull
causing higher high tide ad lower lwer tide = NN Coast UK:
greatest tidal range. - Relatively smaller fetch of 190,000.
o High tide reaches further inland so erode berms, - Relatively low energy coastline – sometimes high during storms from
dunes and cliffs if combined with storms. NE.
o Low tides exposes more of foreshore allowing wave - Mostly constructive waves
erosion or deposition over larger area. - Thus expect low levels of erosion.
o Creates pronounced features = tidal pools, rip - BUT geology. Happisburgh cliffs = glacial till which is permeable, thus
channels etc. saturated by rainwater, slumping.
o Greater movement of sediment due to wider wave - Base of cliffs = unconsolidated boulder clay, freeze thawing.
action. Finer material moved further up beach and - High rates of erosion = average 1m per year and extreme cases 10m.
coarse sediment redistributed more significantly.
- Neap Tides:
South Coast UK: 2m per year
, o Quarter moons. - Low fetch of 100,000.
o Sun + moon at right angles weakening gravitational - Constructive waves.
pool. - But permeable rocks = Chalk.
o Lower high tides and higher low tides = small tidal - Chalk = rolled up of skeleton, zooplankton.
range.
o Wave energy concentrated in smaller area lower on
beach.
o Less erosion + deposition at top of beach so
backshore berns less affected.
o Sediment movement = limited and localized to
foreshore so little change in beach profile unless
storm waves.
Medium - Seasonal changes in wave energy and wind direction.
term – - Summer:
seasonal o Constructive waves.
variation o Wide, flat beaches.
o Multiple berms.
o Sand dunes as dry sand blown inland.
o Finer sediments accumulate.
- Winter
o Destructive waves
o Narrow, steepen beach profile.
o Remove berms
o Offshore bars.
o Coarser sediment – pebbles and shingle
Long - CC, rising sea levels human intervention.
term - Sea level rise + frequent storms:
o Permanent beach erosion.
o Dune loss
o Coastal retreat – narrow, disappear.
- Human intervention.
o Trap sediment, changing beach, width and slope
o Starve sediment downstream causing erosion.
2B.4c Erosion creates distinctive coastal landforms (wave-cut
notches; wave-cut platforms, cliffs, the cave-arch-stack-stump
sequence).
Understand the main types of erosional processes and the landforms
that they create/ Evaluate the importance of wave type, size and
lithology in creating coastal landforms.
Wave cut - HA + abrasion erode base of cliff between low
notches/wa and high tide.
ve cut - Continuous erosion causes cliff to develop a
platforms wave cut notch which is a curved indentation
of about 1 – 2m. undercut area in rock at the
base of cliff.
- As erosion deepens notch, overhanging rocks
becomes stable and eventually collapses.
- Causes the retreat of the cliff and the creation
of a wave cut platform = flat, rocky surface at
the foot of a cliff that is uneroded at low tide.
- Wave cut platform will become more
prominent over time as the cliff continues to
retreat.
Cliffs - Steep slopes that are usually unvegetated.
- Marine erosion of land between the high tide and low tide mark
by HA and abrasion forms a wave cut notch.
- The notch deepens until the overlying rock collapses by mass
movement due to the force of gravity.
- The exposed face forms a cliff.
Cave – arch - Occurs primarily at headlands where
– stack – weaknesses in rock – joints and faults – allow
stump waves to erosde rock more efficiently.
- Old Harry rocks in dorset.
- Cave formation:
o Waves attack weakness in rock through
HA + abrasion.
o Over time, cave is formed as waves
eroded through rock using sand and
other materials to grind in the cracks
until becomes cave.
- Arch formation:
o If cave is eroded all way through is
forms arch.
o Further erosion causes arch to grow
wider and the roof to become more
unstable, forming arch.
- Stack formation:
o Eventually roof of arch collapses due to
2.4 Marine Erosion Creates Distinctive coastal landforms and contributes to coastal landscapes.
2B.4 a Different wave types (constructive/ destructive) influence 2B.4b The importance of erosion processes (hydraulic action, corrosion,
beach morphology and beach sediment profiles, which vary at a abrasion, attrition) and how they are influenced by wave type, size and
variety of temporal scales from short term (daily) through to longer lithology.
periods.
What is 1. When a wave crashes against the cliff face, the air
hydraulic trapped in cracks is compressed by the force of
Constructive waves: action? the wave.
2. Pressure builds up and forces cracks open which
means more air is trapped.
Features - Low energy – dissipates over wide area so 3. This means that a greater force is experienced in
strong backwash. the next cycle of compression.
- Long wave length. 4. This process loosens blocks of rocks that break
- Short height. away from cliff face.
- Low frequency between 6 and 8 waves per
minute. What is 1. Sediment is picked up by breaking waves (usually
- swash is strong whereas backwash is weak so abrasion? during storm) and is thrown against the cliff face.
deposition is greater than erosion. 2. This repeated motion eventually wears away the
Beach - sand and fine material deposited and left cliff.
morphology/sedim behind.
ent profiles - Builds up each other time making it wider and What is 1. Sediment is moved around by waves.
flatter. attrition? 2. Collision between particles causes parts of rock to
- Creates features like berms – ridges of break away.
deposited sediment – and a sandy surface. 3. Becomes smaller and more rounded over time.
- Since backwash is weak, sediment stays at
beach which grows. What is 1. Carbonate rocks (limestones) are vulnerable to
corrosion? solution by rainwater.
2. Dissolve rocks minerals which are carried away by
wave in solution.
Destructive waves: 3. They are vulnerable to erosion by railway and sea
spray.
Features - High energy.
- Short wavelength. Factors affecting erosion:
- Tall breakers that have high downward Factor Affect on erosion
force and strong backwash. Wave type - Destructive waves -> higher downward force, high
- Encouraged by short steep nearshore zone energy environments, stronger backwash = greater
quickly dropping into deeper water so little erosion (HA + abrasion).
energy lost through friction. - Constructive waves ->low energy, strong swash =
- Frequency – 13 to 15 waves per minute. more deposition than erosion, limited HA.
Wave size - Larger waves = more energy = more erosion.
-
- Wave energy increases with wind speech, wind
Beach - Backwash stronger than swash which pulls duration + fetch.
morphology/sediment sand and finer materials away from each, - Bigger waves have greater force to break rocks
profiles dragging out to sea, eroded. apart and hurl larger sediment at cliff face.
- Creates offshore bars where material Lithology - Granite/basalt -> very hard, erode slowly, resistant
deposited. to all processes.
- Particles left behind on each are pebbles or - Sandstone/limestone -> moderate resistance, erode
shingle which creates narrow, steep beach moderately – limestone is vulnerable to erosion.
profile. - Clay/shale -> soft resistance, erode rapidly, easily
broken by HA and saturated by water.
Evaluate the variety of temporal elements involved and their importance in - Chalk -> soft and chemically weak so vulnerable to
shaping out coasts solution and HA.
Short - 2 high tides (6am+ 630pm) and 2 low tides (12:15pm and - Jointe/fractured porous rocks erode faster as water
term – 12:45am). can penetrate + air compression.
daily/tida - High tide -> waves reach further up each affecting
l backshore. Erode berms or cut small notches in upper CASE STUDY – comparing geology + fetch
beach. In storms high tide + destructive waves = dune 2 natural processes causing coastal erosion:
erosion. Finer sediment may be pushed further inland and - Waves from direction of prevailing wind = longest wind direction and
larger sediment may be deposited at wash zone during
thus increase energy, encouraging high energy coastline.
rougher conditions.
- Fetch = distance the wind has blown. Greater distance, more energy
- Low tide -> wave breaks lower on beach near
and thus more powerful wave.
foreshore. Exposes larger surface area to wave energy.
Cusps, pools created in exposed sand/shingle. Find sand
often found in shallow, low tide areas. South West UK:
Daily weather patterns: - Large fetch of 2-6M.
- Calm weather = constructive waves dominate – more - Due to prevailing winds across Atlantic from Gulf of Mexico.
deposition – sand ridges. - Thus expect high levels of erosion.
- Stormy weather = destructive waves – sudden erosion, - High energy coastline
steepen beach, create storm ridges. - BUT SW geology = igneous rocks such as granite = Lansden.
Neap/Spring Tides 28 day cycle: - Granite = interlocking spurs of crystals, high resistance.
- Spring Tides: - Relatively low levels of erosion.
o During full moon and new moon.
o Sun + moon align, increasing gravitational pull
causing higher high tide ad lower lwer tide = NN Coast UK:
greatest tidal range. - Relatively smaller fetch of 190,000.
o High tide reaches further inland so erode berms, - Relatively low energy coastline – sometimes high during storms from
dunes and cliffs if combined with storms. NE.
o Low tides exposes more of foreshore allowing wave - Mostly constructive waves
erosion or deposition over larger area. - Thus expect low levels of erosion.
o Creates pronounced features = tidal pools, rip - BUT geology. Happisburgh cliffs = glacial till which is permeable, thus
channels etc. saturated by rainwater, slumping.
o Greater movement of sediment due to wider wave - Base of cliffs = unconsolidated boulder clay, freeze thawing.
action. Finer material moved further up beach and - High rates of erosion = average 1m per year and extreme cases 10m.
coarse sediment redistributed more significantly.
- Neap Tides:
South Coast UK: 2m per year
, o Quarter moons. - Low fetch of 100,000.
o Sun + moon at right angles weakening gravitational - Constructive waves.
pool. - But permeable rocks = Chalk.
o Lower high tides and higher low tides = small tidal - Chalk = rolled up of skeleton, zooplankton.
range.
o Wave energy concentrated in smaller area lower on
beach.
o Less erosion + deposition at top of beach so
backshore berns less affected.
o Sediment movement = limited and localized to
foreshore so little change in beach profile unless
storm waves.
Medium - Seasonal changes in wave energy and wind direction.
term – - Summer:
seasonal o Constructive waves.
variation o Wide, flat beaches.
o Multiple berms.
o Sand dunes as dry sand blown inland.
o Finer sediments accumulate.
- Winter
o Destructive waves
o Narrow, steepen beach profile.
o Remove berms
o Offshore bars.
o Coarser sediment – pebbles and shingle
Long - CC, rising sea levels human intervention.
term - Sea level rise + frequent storms:
o Permanent beach erosion.
o Dune loss
o Coastal retreat – narrow, disappear.
- Human intervention.
o Trap sediment, changing beach, width and slope
o Starve sediment downstream causing erosion.
2B.4c Erosion creates distinctive coastal landforms (wave-cut
notches; wave-cut platforms, cliffs, the cave-arch-stack-stump
sequence).
Understand the main types of erosional processes and the landforms
that they create/ Evaluate the importance of wave type, size and
lithology in creating coastal landforms.
Wave cut - HA + abrasion erode base of cliff between low
notches/wa and high tide.
ve cut - Continuous erosion causes cliff to develop a
platforms wave cut notch which is a curved indentation
of about 1 – 2m. undercut area in rock at the
base of cliff.
- As erosion deepens notch, overhanging rocks
becomes stable and eventually collapses.
- Causes the retreat of the cliff and the creation
of a wave cut platform = flat, rocky surface at
the foot of a cliff that is uneroded at low tide.
- Wave cut platform will become more
prominent over time as the cliff continues to
retreat.
Cliffs - Steep slopes that are usually unvegetated.
- Marine erosion of land between the high tide and low tide mark
by HA and abrasion forms a wave cut notch.
- The notch deepens until the overlying rock collapses by mass
movement due to the force of gravity.
- The exposed face forms a cliff.
Cave – arch - Occurs primarily at headlands where
– stack – weaknesses in rock – joints and faults – allow
stump waves to erosde rock more efficiently.
- Old Harry rocks in dorset.
- Cave formation:
o Waves attack weakness in rock through
HA + abrasion.
o Over time, cave is formed as waves
eroded through rock using sand and
other materials to grind in the cracks
until becomes cave.
- Arch formation:
o If cave is eroded all way through is
forms arch.
o Further erosion causes arch to grow
wider and the roof to become more
unstable, forming arch.
- Stack formation:
o Eventually roof of arch collapses due to
