2.a - coastal landforms develop Flashcards
where do swash-aligned beaches form?
form in low energy environments such as bays that are affected by waves arriving roughly PARALLEL to the shore
swash-aligned sediment moves up and down rhe beach with little lateral transfer
where do drift-aligned beaches form?
orm where the waves approach the coast at an angle.
longshore drift moves sediment along the beach culminating in the formation of a spit
which landforms are associated with swash-aligned beaches?
bay-head beaches/curved beaches
which landforms are associated with drift-aligned beaches?
ridges of sand/shingle beaches
erosional landforms - CLIFFS AND SHORE PLATFORMS
cliffs are usually at a steep angle of more than 40° but may be vertical/overhanging
they are often found at the coast with a shore platform
what is a wave cut notch?
may be found at the base of cliffs due to long-term wave-attack and is the point at which cliffs are undercut
the overhanging cliff face will eventually fall under the force of gravity, driven by subaerial weathering and mass movement processes.
may be rapidly created and pronounced on coastlines with a microtidal range (less than 2m tidal range) as the sea’s erosive energy is concentrated over a smaller area.
when and how is a shore platform created?
as a cliff retreats over time
it is usually covered at high tide.
1. the sea attacks a weakness in the base of the cliff (e.g. a joint in chalk)
2. a wave cut notch is created by erosional processes such as hydraulic action and abrasion
3. the cliff retreats inland
4. the material from the collapsed cliff is eroded and transported away, this leaves a wave cut platform
5. the process repeats over time
how is cliff morphology influenced by the geology of a coastline?
most particularly by the STRUCTURE and LITHOLOGY of the rock type as this will affect how cliffs respond to erosion and sub-aerial processes.
cliffs receede mainly during storms when they are subject to attack from wave erosion, and hydraulic pressure and abrasion dominate.
when do cliffs mainly receede?
cliffs receede mainly during storms when they are subject to attack from wave erosion, and hydraulic pressure and abrasion dominate.
how are cliffs formed?
erosional processes:
- abrasion
- hydraulic action
- pounding
- corrosion
weathering processes:
- freeze-thaw
- salt crystallisation
- carbonation
erosional landforms - CAVES
caves are natural cavities in rock faces which form when weaknesses in local geology are attacked by marine erosion.
they are common in areas in which the rock has many joints, faults or weaknesses.
caves are less likely to form in weaker rocks as the cave will likely collapse soon after it is created and undercuts the rock above.
they occur when waves force their way into cracks in the cliff face. the water contains sand and other materials that grind away at the rock until the cracks become a cave. hydraulic action is the predominant process.
erosional landforms - ARCHES
a sea arch is an opening through a mass of rock, commonly seen at the coast where waves have eroded through a cave.
arches form when caves extend through headlands due to powerful wave action.
the arch will gradually become bigger untill it can no longer support the top of the arch. when the arch collapses, it leaves the headland on one-side and a stacks on the other.
erosional landforms - STACKS
coastal promontories may be dissected over time
a natural arch roof may collapse as it grows thinner through prolongued attack by weathering and erosion processes to leave a stack, an isolated pillar of rock which rises steeply from the sea, which stands separately from the cliffed coast that is was previously connected to.
the stack will be attacked at the base in the same way that a wave-cut notch is formed
erosional landforms - STUMPS
further erosion at the base of a stack may cause further collapse, leaving a small, flat portion of the original stack as a stump.
this may only be visible at low tide.
erosional landforms - GEOS
a geo, or a coastal gorge, is created when a faultline is differently eroded to form a narrow inlet, or gulley.
they are created by the wave driven erosion of cliffs along faults and bedding planes in the rock
geos can have caves at their heads
those caves may collapse, extending the geo, or leaving depressions inland from the geo
