Types of Cliffs and Their Formation

Cliffs are prominent features of coastal landscapes and their shapes are determined by the interplay of marine and sub-aerial processes, as well as the underlying rock type.

Different Types of Cliffs

1. 90° Profile Cliffs: These have a steep, vertical face due to strong marine erosion at the base.

2. 40° Profile Cliffs: These have a more gentle slope, often due to a balance between marine and sub-aerial processes.

3. Bevelled Cliffs: These have a steep lower section and a more gentle upper section, resulting from different erosion rates.

4. Plunging Cliffs: These descend directly into deep water, with waves hitting them directly.

Definition: Sub-aerial processes refer to weathering and erosion that occur above the water level, such as frost action and rainfall.

Formation of Cliff Types

• 90° Profile Cliffs: Form in areas with strong marine erosion and resistant rock.
• 40° Profile Cliffs: Develop when there's a balance between marine erosion and sub-aerial weathering.
• Bevelled Cliffs: Result from differential erosion rates, with less resistant rock at the top.
• Plunging Cliffs: Form in areas of exceptionally deep water, where wave energy is not dissipated before reaching the cliff.

Highlight: The type of rock and the balance between marine and sub-aerial processes determine the shape of cliffs.

Slope-Over-Wall Cliffs

These cliffs have a unique formation process:

1. Initial cliff formation by marine processes during warm periods.
2. Sea level drop during ice ages leads to sub-aerial processes dominating.
3. Permafrost causes solifluction, creating a gradient slope at the base.
4. Freeze-thaw processes at the top create a bevelled profile.
5. Rising sea levels remove the soliflucted material, revealing the original cliff face.

Vocabulary: Solifluction - The slow downslope movement of water-saturated sediment due to recurrent freezing and thawing of the ground.

Beach Formation and Profiles

Beaches are dynamic coastal features that change in response to wave action and sediment movement. Understanding beach formation is crucial in coastal landforms PDF studies.

Swash-Aligned Beaches

Swash-aligned beaches form when:

• Waves approach perpendicular to the shore.
• There are no prevailing winds, resulting in no longshore drift.
• The swash and backwash are aligned, limiting longshore sediment movement.
• They are common on indented coastlines where longshore sediment movement is limited.

Example: Cardigan Bay in Wales is an example of a coastline with swash-aligned beaches.

Drift-Aligned Beaches

Drift-aligned beaches are the stereotypical beach type and form when:

• Waves approach at an oblique angle to the shore.
• Sediment is moved via longshore drift.
• Waves break at different times along the beach due to imperfect refraction.
• They are associated with the formation of spits.

Vocabulary: Longshore drift - The movement of beach material along the coast by wave action.

Storm Cut and Swell Fill Beach Profiles

Beaches exhibit different profiles depending on wave conditions:

1. Storm Profile:

   • Created by steep, destructive waves.
   • Sediment is moved offshore.
   • Quick succession of waves reduces swash ability to transport sediment.
   • Results in a gentler overall gradient.

2. Swell Profile:

   • Created by constructive waves with long intervals between them.
   • Strong swash takes sediment from lower beach and deposits it higher up.
   • Creates a steeper overall gradient.

Highlight: The alternation between storm and swell profiles demonstrates the dynamic nature of beach environments.

Beach Ridge and Berm Formation

• Beach ridges form as waves are refracted on approach to the seafloor.
• Berms develop at the upper limit of wave action during normal conditions.

Definition: A berm is a nearly horizontal portion of the beach formed by the deposit of material by wave action.

Sand Dune Formation and Coastal Depositional Features

Sand dunes are important coastal landforms that develop in areas with abundant sand supply and onshore winds. Their formation is a key topic in types of coastal landforms with pictures.

Sand Dune Formation Process

1. In macrotidal areas, sand dries out during low tide.
2. Wind transports dry sand through saltation.
3. Sand accumulates around obstacles on the beach, such as vegetation or debris.
4. Embryo dunes form on the strand line, stabilized by pioneer plants like marram grass.
5. Fore dunes develop behind embryo dunes, featuring yellow dunes with more diverse vegetation.
6. Grey dunes form further inland, with a more stable environment and diverse plant communities.

Vocabulary: Saltation - The bouncing movement of sand particles caused by wind action.

Coastal Vegetation Succession

The vegetation on sand dunes changes as you move inland:

1. Blue-green algae and sea couch grass on embryo dunes.
2. Marram grass on fore dunes.
3. Sea buckthorn and other shrubs on yellow dunes.
4. Heath plants dominating grey dunes.

Highlight: The succession of plant communities on sand dunes reflects the changing environmental conditions from the beach to inland areas.

Other Coastal Depositional Features

• Spits: Form where longshore drift deposits material along a coastline, often at the mouth of estuaries.
• Salt Marshes: Develop in sheltered areas where fine sediment can accumulate and halophytic plants can grow.
• Shingle/Pebble Deposits: Form in shallow water in the lee of headlands.

Example: The formation of spits, such as Spurn Head in East Yorkshire, UK, illustrates the power of longshore drift in shaping coastal landscapes.

These coastal depositional features play crucial roles in coastal ecosystems and provide natural defenses against erosion and flooding.

Bays, Headlands, and Wave-Cut Platforms

Coastal landscapes are shaped by the interaction of waves with different rock types, creating distinctive features such as bays, headlands, and wave-cut platforms.

Bays and Headlands Formation

Bays and headlands form along coastlines with alternating bands of hard and soft rock. The process involves:

1. Waves eroding the coastline through hydraulic action and attrition.
2. Soft rock erodes faster, creating bays.
3. Hard rock resists erosion, forming headlands that stick out to sea.
4. During calm periods, sheltered bays allow for deposition, forming beaches.

Highlight: The differential erosion of hard and soft rock is key to the formation of bays and headlands.

Wave-Cut Platforms

Wave-cut platforms are flat areas of rock formed at the base of cliffs. Their formation process includes:

1. Waves form a wave-cut notch at the cliff base through undercutting.
2. As the notch grows larger, the cliff eventually collapses due to lack of support.
3. The process of undercutting and collapse repeats, causing the cliff to retreat and increase in height.
4. A wave-cut platform is exposed at low tide as the cliff continues to retreat.

Vocabulary: Wave-cut notch - An indentation formed at the base of a cliff by wave erosion.

Caves, Arches, Stacks, and Stumps

These features form through the continued erosion of headlands:

1. Waves enter faults or cracks in the headland, eroding through hydraulic action and abrasion.
2. A cave forms and widens due to marine erosion and sub-aerial processes.
3. The cave may erode through the headland, creating an arch.
4. The arch widens until it collapses, leaving a stack.
5. Continued erosion at the base of the stack leads to its collapse, forming a stump.

Example: The formation sequence of caves, arches, stacks, and stumps can be observed in many coastal areas, such as the Old Harry Rocks in Dorset, England.