Coasts EQ1 And Most Formation Questions Are EQ2 Flashcards
Explain how geological structure affects the development of coastal landforms
Geological structure can refer to concordant and discordant coastlines
It can also refer to the lithology (physical characteristics of a rock/rocks in a particular area)
Concordant coastlines are where the geology runs parallel to the coast and is associated with landforms such as covers as well as Dalmatian and Haff type coastlines
In some cases, such as Lulworth Cove, the band of resistant rock can be exploited by fluvial eriosion
(Fluvial erosion is the detachment of material of the river bed and the sides. Erosion starts when the flow energy of the water exceeds the resistance of the material of the river bed and banks.)
Complex deposition Al features such as spits are more likely to be found on concordant coasts where longshore drift can operate
Discordant coasts are where the geology runs at right angles to the coast and creates landforms such as bays and headlands reflecting variations in rock resistance
The horizontal bedding of resistant rocks such as sandstone leads to vertical cliffs
The exact profile of vertical cliffs can also be determined by the joint pattern of the rock, as well as well-jointed granite or limestone creating blocky profiles
Isostatic vs eusostatic change
Isostatic is the result of an increase/decrease of the land
Eusostatic is when water moves in relation to the land
Explain the formation of the cliff profile shown in photograph 3A (6)
AO1
* Cliff profiles are a consequences of wave attack, sub-aerial processes and the nature of the materials
* Wave action undercuts cliffs through abrasion and hydraulic action
* Softer and more jointed rocks will erode more rapidly because of lower levels of physical strength and cohesion and smaller
surface areas
* Beaches can act as ‘shock absorbers’ to dissipate wave energy and protect cliff lines
AO2
* This cliff is low – about 6 meters and low angled, suggesting rapid erosion rates
* The boulder clay shown is soft and relatively easily eroded
* The impact of abrasion employing the large boulders, seen in the photograph, will make cliff erosion very rapid
* There are clear signs of rotational slumping on the cliffs, suggesting that subaerial processes are significantly de-stabilised
by wave action at the cliff base
Spit formation
- longshore drift carries material along a beach
- A sudden change in coastal shape will initiate a deposition of material
- The presence of a river , or extension to water currents will prevent the spit extending
- Can form recurved and double spits
Barrier beaches (bars)
- Longshore drift extends a spit between two headlands
- These barrier beaches trap water behind as a lagoon
- When it becomes separated from the mainland, it forms a barrier island
Cuspate Forelands formation
- longshore drift occurs in opposite directions
- Sediment is deposited at the point where they meet
- Vegetation then grows and stabilises these landforms
Sand dunes formation
Recap from previous Learning
Offshore bars formation - effectively a spit that is going off a bay
- destructive waves erode sand and coarse sediment from the beach
- The strong backwash pulls it offshore and then deposits it as a bar
- These cause waves to break further out to sea
Tombolo formation
- Longshore drift creates a beach between an island and the mainland
- Sometimes they are covered at high tide
Swash aligned beach formation
- Sediment moves up and down the beach with little lateral transfer
- These occur in tight bays and are so protected from the effects of LSD (longshore drift)
Drift aligned beach
- Sediment is transferred along the coast by longshore drift
2.these beaches tend to be longer and have graded material (I e sediment becomes finer further along the beach)
Offshore bars formation
- Destructive waves erode sand and coarse sediment from the beach
- The strong backwash pulls it offshore and then deposits it as a bar
- This causes waves to break further out at sea
