Coastal Landscapes and Geology
1. Explain how the geological structures influences the development of
Costal landscapes:
1. Rock Type (Lithology)
Hard Rocks (e.g., granite, basalt) are more resistant to erosion, which
leads to the formation of features like headlands, cliffs, and wave-cut platforms.
These types of coastlines are rugged and tend to erode more slowly.
Soft Rocks (e.g., clay, sandstone) are more easily eroded, creating features
like bays and beaches. Soft rock areas tend to retreat more quickly due to
erosion from wave action.
2. Faulting and Folding
Faults create zones of weakness in the coastline, where waves can erode
the rock more rapidly, forming caves, arches, and stacks.
Folding occurs when rocks are compressed and bend. Uplifted, folded rock
may form headlands or cliffs, while the less resistant areas erode more quickly,
creating bays or inlets.
3. Rock Dip
The angle at which rock layers are tilted (the dip) affects coastal stability:
Seaward dip: Rock layers dipping towards the sea tend to be less stable,
leading to the formation of gentler cliffs that are prone to landslides or slumping.
Landward dip: Rock layers dipping inland create steep, stable cliffs
because erosion tends to occur at the base, leading to undercutting and eventual
collapse.
Horizontal layers: These can form high, vertical cliffs, which erode at the
base, often leading to large collapses as erosion undercuts the cliff.
4. Concordant vs. Discordant Coastlines
Concordant coastlines occur when rock layers run parallel to the shoreline.
Erosion rates are relatively even, but weak points in the rock can lead to features
like coves (e.g., Lulworth Cove).
Discordant coastlines occur when rock layers run perpendicular to the
coast. Hard and soft rocks erode at different rates, creating alternating
headlands and bays (e.g., the Dorset Coast).
5. Joints and Bedding Planes
Joints (natural cracks) provide zones of weakness in rocks where waves
can force air and water into the rock, leading to erosion and the formation of
features like blowholes and geos.
Bedding Planes (horizontal layers of rock) also create weaknesses that
waves can exploit. Erosion along bedding planes can result in the formation of
wave-cut platforms
, In Summary:
Geological structures such as rock type, faulting, folding, rock dip, and the
alignment of rock strata significantly shape the coast. These factors dictate how
quickly parts of the coastline erode, the type of coastal features that form, and
the overall landscape of a coastline. Understanding these elements helps explain
the formation of cliffs, bays, headlands, and more.
2. Outline the physical factors that influence rates of coastal recession
Coastal recession, or the retreat of the coastline due to erosion, is
influenced by several physical factors. Here’s an outline of the key factors:
1. Geology (Rock Type and Structure)
Lithology (Rock Type): Hard rocks like granite are more resistant to
erosion, while soft rocks like clay erode more quickly, leading to faster coastal
recession in soft rock areas.
Rock Structure: The presence of joints, bedding planes, and faults creates
weaknesses in rocks that waves can exploit, accelerating erosion.
2. Wave Energy
High-energy waves (Destructive Waves): These carry more energy and are
more effective at eroding coastlines, especially during storms.
Low-energy waves (Constructive Waves): These are less powerful and tend
to deposit material rather than erode the coast.
3. Tides
Tidal Range: A large tidal range means waves can affect a larger area of
the coast, increasing the overall rate of erosion.
High Tides: During high tides, waves reach further up the shore, affecting
areas that are otherwise protected.
4. Weathering
Mechanical Weathering (e.g., freeze-thaw): This breaks down rock, making
it more vulnerable to erosion.
Chemical Weathering (e.g., carbonation): This weakens rocks by dissolving
minerals, especially in limestone or chalk.
Biological Weathering: Plant roots and burrowing animals break down rock,
increasing susceptibility to erosion.
5. Climate and Weather Conditions
Storms and Extreme Weather: Storm surges and high winds increase wave
energy, leading to more rapid erosion.
Rainfall: Heavy rainfall can lead to saturation of cliffs, making them more
prone to collapse through mass movement.
