The formation and characteristics of cliffs

Cliffs are steep rock faces along coastlines, shaped by a variety of factors that influence their profile and stability.

Factors influencing cliff profiles

• Geological structure - The type and arrangement of rock layers affect how cliffs form and erode. For instance, rocks with low resistance erode more easily and cannot support overhangs.
• Jointing and dip angle - Weaknesses in the rock, such as joints or cracks, create points of vulnerability. The angle at which rock layers are tilted (dip) can also control the overall shape of the cliff.
• Subaerial and marine processes - Weathering from rain, wind, and temperature changes (subaerial) combines with wave action (marine) to erode cliffs over time.
• Undercutting - Waves erode the base of cliffs, creating overhangs that may eventually collapse.
• Rates of removal - The speed at which eroded material is carried away impacts how quickly the cliff retreats.
• Stage of development - Younger cliffs may be steeper, while older ones show more gradual slopes due to prolonged erosion.

The development of stacks and stumps

Stacks are isolated rock pillars standing in the sea, formed through the progressive erosion of coastal headlands. Their creation involves a sequence of stages driven by wave energy and rock weaknesses.

Stages of stack and stump formation

1. Cave formation - Wave refraction focuses energy on the sides of headlands, exploiting weaknesses like joints or cracks in the rock to form caves.
2. Arch creation - As caves on opposite sides of a headland enlarge, they eventually meet, forming a natural arch through the headland.
3. Stack emergence - Continued erosion, weathering, and mass movements cause the arch's roof to collapse, leaving a standalone stack.
4. Stump development - Over time, relentless wave action erodes the stack down to a low-lying stump.

The evolution of wave-cut platforms

Wave-cut platforms, also known as shore platforms, are flat or gently sloping rock surfaces at the base of cliffs, created by wave erosion. They are commonly found in high-energy coastal environments.

Characteristics of wave-cut platforms

• Types of platforms - Include intertidal platforms (exposed between high and low tides), high-tide platforms, and low-tide platforms.
• Dimensions and slope - Typically less than 500 metres wide with a gentle slope of around 1 degree.
• Formation process - Waves erode the base of a cliff, causing it to retreat over time. This leaves behind a lengthening platform while the cliff angle becomes less steep, shifting the dominant erosion from marine to subaerial processes.
• Alternative origins - Some platforms may result from frost action, salt weathering, or biological processes during periods of lower sea levels or different climatic conditions.

The features and formation of beaches

Beaches are accumulations of sediment, such as sand or shingle, found in sheltered coastal areas or regions with a plentiful supply of material.

Formation and influencing factors of beaches

• Sediment accumulation - Beaches form in areas protected from strong wave action or where there is a large input of sediment.
• Material characteristics - The size, shape, and composition of sediment affect beach form. Sediment size affects beach profile through its percolation rate.
• Tidal range - The difference between high and low tides influences how sediment is distributed across the beach.
• Wave characteristics - The energy and direction of waves shape the beach profile.

Key features of a beach profile

• Storm beach - A prominent ridge of larger sediment, formed at the level of the highest spring tides, often semi-permanent.
• Berms - Small ridges built up by successive tides or storms, marking different water levels on the beach.
• Cusps - Semi-circular hollows typically found in shingle or at the boundary between shingle and sand.

The structure and formation of spits

Spits are elongated ridges of sand or shingle attached to the land at one end, extending into the sea or across a bay.

Characteristics and formation of spits

• Location - Commonly found on indented coastlines with alternating headlands and bays, or near river mouths like estuaries, where wave energy is reduced.
• Structure - Spits have a narrow, attached end called the proximal end, and a broader, free end known as the distal end, often featuring smaller hooked curves called recurves.
• Formation process - Waves transport sediment along the coast. Where wave energy decreases, such as at a bay or river mouth, sediment is deposited, building up the spit over time.
• Curved shape - Spits often bend due to wave refraction, where waves change direction as they approach shallower water. Cross-currents or occasional storm waves can also contribute to the hooked formation at the distal end.