3.3.1 Landforms Of The Coast Flashcards
What processes cause formation of wave cut platforms?
At high-energy coastlines, hydraulic action and abrasion can cause the formation of wave-cut platforms
Explain the process of creation of a wave cut platform?
Powerful destructive waves attack the base of the cliff at high tide
The hydraulic action and abrasion create a wave-cut notch which over time increases in size
This is called undercutting
Eventually the overhang created by the undercutting collapses due to weathering and gravity
The cliff retreats, leaving a wave cut platform that is exposed at low tide
Explain the chain of processes involved in formation of cave, arch and stack
Wave refraction concentrates wave energy onto the headland and can contribute to the formation of caves, arches, stacks and stumps
Joints in the headland are susceptible to erosion by hydraulic action
Over time the joints widen forming a cave which is enlarged by hydraulic action and abrasion
Eventually erosion cuts through the headland forming an arch
The roof of the cave will eventually collapse due to gravity and the lack of support
This leaves a stack which will over time be eroded by weathering, abrasion and hydraulic action to form a stump
Explain the chain of beach formation (drift-aligned and swash-aligned)
Beaches can be drift-aligned or swash-aligned
Drift-aligned beaches form where longshore drift moves the sediment along the beach as waves approach at an oblique angle
This will often culminate in a spit where the coastline changes direction
Swash-aligned beaches form where the energy is low
The waves are more parallel to the shore in swash-aligned environments so there is very little horizontal or lateral movement of sediment
Explain formation of a spit
Spits are created due to longshore drift
Sediment is transported by waves along a coastline
When the coastline changes direction the waves no longer have the energy to carry the sediment and it is deposited
The build up of deposited sediment out to sea, often into an estuary, is called a spit
The spit often has a curved end or hooks due to a secondary prevailing wind
Explain formation of tombolo and bar
As spits form across an estuary or around a headland there can also be the formation of tombolos and bars where the sediment meets either an island or the opposite side of a headland respectively
These are formed in the same way, through longshore drift and deposition
Bars can also form offshore
These are raised ridges of sediment away from the shore
They form where the sediment level is high and the sea is shallow
Bars that form as spits extend to join two headlands are also known as barrier beaches
Water trapped behind the barrier beach is called a lagoon
Explain formation of salt marshes
Behind spits and barrier beaches the area is very sheltered, tidal currents and river currents meet leading to lots of deposition
This can lead to the formation of salt marshes
Salt-tolerant species colonise these sheltered, flat muddy areas. During the vegetation succession, halosere (algae and zosters), salt marshes develop
They are covered at high tide and exposed at low tide
Explain formation of sand dunes
Deposition can also lead to the formation of sand dunes
Sand dunes are formed in areas where there is a large quantity of sand, a large tidal range and onshore prevailing winds
When sand is trapped towards the back of the beach due to an obstacle dunes will develop
Pioneer plant species hold the sand together and stabilise the dune. Psammosere vegetation succession. Salt-tolerant species such as littoral algae and glasswort.
Other plants are then able to thrive in the environment which leads to the development of the dune ecosystem, this is called plant succession
