Destructive waves concentrate hydraulic action and abrasion around the foot of an exposed cliff.
Repeated erosion cuts a wave-cut notch close to the level reached by breaking waves.
The notch deepens until the unsupported overhang becomes unstable.
Weathering, joints and gravity help the overhang collapse.
Waves remove or reduce the fallen debris, exposing the cliff foot to renewed attack.
Repeated undercutting and collapse move the cliff line landward.
The former cliff base remains as a gently sloping rocky wave-cut platform.
Note
The platform records cliff retreat because it occupies ground that once supported the cliff.
Its surface may contain rock pools, joints and abrasion marks that continue to be modified by tides and waves.
Platform width is limited
A wider platform makes waves break farther offshore, reducing the energy that reaches the cliff.
Weathered debris can temporarily protect the cliff foot until waves remove it.
Platform gradient, tidal range and joint pattern affect where wave energy is concentrated.
Example
At Flamborough Head in eastern England, resistant chalk forms high cliffs and broad intertidal rock surfaces.
Joints and bedding planes still provide lines of weakness for notch formation and collapse.
Cliffs Reflect Rock and Process
Cliffs form where erosion removes material faster than deposition can protect the shore.
Rock resistance influences the rate of retreat, but structure determines how failure occurs.
Vertical joints encourage block fall, while seaward-dipping beds may support sliding.
Weak, saturated sediment is especially susceptible to rotational slumping.
A beach can absorb wave energy and slow cliff erosion, while beach loss exposes the cliff foot.
Common Mistake
A steep cliff does not prove that erosion is rapid because resistant rock can maintain a near-vertical face for long periods.
Retreat rate and cliff angle must be explained separately.
Caves, Arches and Stacks Follow Weaknesses
A headland is progressively breached
Wave refraction concentrates energy on the sides and tip of a headland.
Hydraulic action and abrasion enlarge a joint, fault or weaker rock band into a cave.
A cave may deepen from one side or meet another cave from the opposite side.
When erosion cuts through the headland, an arch forms.
Weathering weakens the arch roof while gravity places it under stress.
Roof collapse separates a pillar of rock from the headland, producing a stack.
Further undercutting and weathering reduce the stack to a lower stump.
Tip
The sequence is not automatic because it requires a suitable weakness, sustained wave attack and enough time.
Name the process at each transition instead of reciting cave, arch, stack and stump as a list.
Stacks are temporary remnants
The seaward face receives direct wave attack and may be notched near water level.
Salt weathering, wetting and drying, and biological activity weaken exposed surfaces above the waterline.
The stack eventually collapses when its base or structural weaknesses can no longer support it.
Example
Old Harry Rocks beside Studland in southern England are chalk stacks and stumps developed along a jointed headland.
Their form reflects both resistant chalk and weaknesses that wave erosion can enlarge.
Beaches Are Mobile Sediment Stores
A beach is an accumulation of unconsolidated sediment within the zone affected by waves and tides.
Sediment may consist of sand, shingle, shell fragments or mixed material.
Inputs can come from rivers, cliff erosion, offshore stores and littoral drift.
Outputs include transport alongshore, offshore loss, wind transfer to dunes and extraction by people.
Note
Beach form is an outcome of the sediment budget and recent wave conditions.
A profile measured once is therefore a snapshot rather than a permanent coastal shape.
Constructive waves build berms
A relatively strong swash carries sediment up the beach.
A weaker backwash removes less material, creating net deposition.
Repeated deposition can build a ridge or berm near the limit of normal swash.
Coarser sediment usually forms steeper profiles because rapid infiltration weakens backwash.
Fine sand retains more surface flow and is commonly associated with gentler profiles.
Common Mistake
Grain size influences beach gradient, but wave history, sediment supply and tidal range also matter.
Do not infer one cause from a profile without supporting evidence.
Storms and calmer periods reshape the profile
Storm waves can erode the upper beach and move sediment offshore into bars.
Offshore bars make later waves break earlier and can reduce the energy reaching the shore.
Calmer constructive waves may return some bar sediment to the beach.
Seasonal recovery depends on whether sediment remains inside the coastal system.
Tip
Use a sediment budget to explain beach change: identify inputs, transfers, temporary stores and outputs.
The same storm can narrow one beach while feeding a bar or another section of coast.
A Spit Develops Where Transport Continues Past Land
Littoral drift builds a projecting ridge
Oblique wave approach moves sediment along the shore through littoral drift.
Where the coastline changes direction or crosses an estuary mouth, the transport path may continue into open water.
Wave energy falls in the more sheltered water, so sediment is deposited.
Continued supply lengthens the deposit from the coast to form a spit.
The distal end may become recurved when wave direction changes or tidal currents modify deposition.
Sheltered water behind the spit encourages fine sediment to settle.
Mudflats and salt marshes may develop if tidal conditions and vegetation permit.
A spit remains attached to the mainland at one end, unlike an offshore bar.
A river or strong tidal current can keep an estuary mouth open and prevent the spit from closing the bay.
Example
Spurn Head projects southward across the Humber estuary because sediment from the eroding Holderness coast is transported alongshore.
Its history of growth, breaching and re-formation shows that a spit is dynamic rather than fixed.
Landforms Depend on Connected Conditions
Erosional forms need exposure and weakness
Cliffs, platforms and stacks develop where wave energy reaches rock that contains exploitable weaknesses.
Low sediment cover allows waves to attack the rock directly.
Subaerial weathering and mass movement accelerate failure above the waterline.
Tidal range influences the vertical zone over which erosion operates.
Note
A landform name describes shape, while a strong explanation identifies the processes, material and sequence that produced it.
Similar shapes can therefore form at different rates and through different combinations of controls.
Depositional forms need surplus sediment
Beaches and spits require an available sediment source and a transport pathway.
Deposition occurs where energy or transport competence falls.
Vegetation can trap fine sediment in sheltered zones behind depositional landforms.
Engineering that blocks littoral drift may enlarge an updrift beach but starve a downdrift coast.
Example
Holderness and Spurn form one connected system: cliff erosion supplies material, littoral drift transfers it, and deposition stores part of it at the Humber.
Changing any one part of that chain can alter landforms elsewhere.
Field Evidence Can Test a Formation Sequence
A cliff profile, notch and fresh debris indicate active undercutting and collapse.
Rounded and progressively smaller clasts alongshore can support an attrition and transport explanation.
Changes in beach width, grain size and berm position reveal recent erosion or deposition.
Spit orientation and sediment grading can indicate the dominant transport direction.
Repeated measurements are stronger than one observation because coastal forms vary with tide, season and storms.
Tip
Match each observation to a process before using it as evidence for a formation sequence.
Record tide, recent weather and location because coastal evidence changes across space and time.
Wave Refraction Links Erosional and Depositional Forms
Wave fronts bend as their shallow-water sections slow against an irregular coastline.
Energy converges on headlands, increasing the likelihood of cliffs, caves and stacks.
Energy disperses in bays, encouraging beaches to accumulate where sediment is available.
The growing contrast between headland erosion and bay deposition can make the coastline more regular over time.
Common Mistake
Refraction redistributes wave energy but does not guarantee a landform because geology and sediment supply still control the response.
Use it as one link in a multicausal explanation.
Check Your Understanding
Active recall
How does repeated notch formation produce both cliff retreat and a wave-cut platform?
What conditions allow a cave to develop into an arch and stack?
Why can a beach become narrower after a storm without losing all sediment from the coastal system?
How do littoral drift, a change in coastline direction and sheltered water combine to form a spit?
What field evidence would distinguish an active process from a relict coastal form?
