Coasts EQ2

Question 1

What are constructive and deconstructive waves?

Answer 1

Deconstructive waves have a weak swash and strong backwash.

Constructive waves have a strong swash and weak backwash.

Question 2

What is hydraulic action?

Answer 2

Shear power of the waves wear away the cliff face.

Question 3

What is abrasion?

Answer 3

Known as corrasion. Waves break at the base of the cliff, throwing sediment at it.

Question 4

What is attrition?

Answer 4

Rocks hit each other, forming smaller, rounder rocks.

Question 5

What is corrosion?

Answer 5

Also known as solution. Rock particles dissolve due to weak alkaline waters.

Question 6

How is a wave cut notch and platform formed?

Answer 6

1) The sea attacks the base of the cliff between the high and low water mark.

2) A wave-cut notch is formed by erosional processes such as abrasion and hydraulic action - this is a dent in the cliff usually at the level of high tide.

3) As the notch increases in size, the cliff becomes unstable and collapses, leading to the retreat of the cliff face.

4) The backwash carries away the eroded material, leaving a wave-cut platform.

5) The process repeats. The cliff continues to retreat.

Question 7

What is the cave, arch, stack, stump sequence?

Answer 7

1) Cracks are widened in the headland through the erosional processes of hydraulic action and abrasion.
As the waves continue to grind away at the crack, it begins to open up to form a cave.

2) The cave becomes larger and eventually breaks through the headland to form an arch.

3) The base of the arch continually becomes wider through further erosion, until its roof becomes too heavy and collapses into the sea. This leaves a stack (an isolated column of rock).

4) The stack is undercut at the base until it collapses to form a stump.

Question 8

How do headlands and bays form?

Answer 8

Bands of soft rock such as clay and sand are weaker therefore they can be eroded quickly. This process forms bays. A bay is an inlet of the sea where the land curves inwards, usually with a beach. Hard rock such as chalk is more resistant to the processes of erosion. When the softer rock is eroded inwards, the hard rock sticks out into the sea, forming a headland.

Question 9

What is traction?

Answer 9

Large and heavy rocks roll along the seabed.

Question 10

What is saltation?

Answer 10

Smaller, lighter rocks bounce along the seabed.

Question 11

What is suspension?

Answer 11

Lighter sediment is carried by the flow of water.

Question 12

What is solution?

Answer 12

Dissolved sediment carried by the flow of water.

Question 13

What’s the process of longshore drift?

Answer 13

The movement of material along the shore by waves. It happens when the waves approach the beach at an angle. The swash carries material up the beach.

Question 14

How are spits formed?

Answer 14

An extended stretch of sand or shingle jutting out in the sea from the land. Form drift-aligned beaches. Sand and shingle are moved along the coast by longshore drift. If the coastline changes direction, sediment will build up and become deposited (e.g. due to an estuary mouth), forming a spit. The outward flow of the river will prevent the spit from extending the full width of an estuary. The end of the spit curves round and carries the material around behind the spit which is known as a recurved spit and forms salt marshes behind them.

e.g. Spurn head

Question 15

How are offshore bars formed?

Answer 15

Long ridge of sand or pebbles formed a short distance out to sea parallel to the coast in an offshore zone. They form from sediment eroded by destructive waves and carried seawards by backwash.

Question 16

How are swash aligned beaches formed?

Answer 16

Form in low energy environments e.g. bays. Sediment moves up the beach with lateral transfer. They tend to form curved concave beaches. The beach face is orientated parallel to the fronts of dominant waves.

e.g Chesil beach in Dorset

Question 17

How are drift aligned beaches formed?

Answer 17

Forms when waves approach the coast at an angle. Sediment transferred by longshore drift along the coast. Often form a spit.

Question 18

How are barrier beaches formes?

Answer 18

Where a spit or beach extends across a bay to join two headlands. Formed from rounded shingle deposited. Barrier beaches can trap lagoons behind them.

Question 19

How is a tombolo formed?

Answer 19

A tombolo is formed when a spit connects the mainland coast to an island. A spit is a feature that is formed through deposition of material at coastlines. The process of longshore drift occurs and this moves material along the coastline.

Through this process material is constantly moved along the coastline. When the coastline changes direction or there is a river estuary the process of longshore drift continues. This causes the material to be deposited in a long thin strip that is not attached to the coast and is known as a spit. If this feature moves in the island’s direction and connects it to the mainland, it becomes a tombolo.

Question 20

How are double spits formed?

Answer 20

Double spits are where two spits extend out in opposite directions from both sides of the bay, towards the middle. They form where longshore drift is operating in different directions on opposite sides of the bay.

Question 21

How are cuspate forelands created?

Answer 21

A cuspate foreland is a triangular-shaped headland that extends out from the main coastline. It occurs where the coast is exposed to longshore drift from opposite directions. Sediment is deposited at the point where the two meet which forms a natural triangular shape as it builds up. Vegetation begins to grow on the deposited sediment, it helps to stabilise the landform and protect it from storms that could erode. Cuspate forelands can be smaller or they can be larger features.

Question 22

What is mechanical weathering?

What is biological weathering?

What is chemical weathering?

Answer 22

Also known as freeze thaw. Occurs when water enters a crack or joint. Then freezes in cold weather. It expands about 10%, it exerts pressure, forcing the rock apart.

The process in which plants, animals and bacteria break down rocks into smaller pieces.

Erosion of rocks caused by a chemical reaction e.g carbonation.

Question 23

What is mass movement and the different categories?

Answer 23

Movement of surface material caused by gravity.

Flows and slides.

Question 24

What is soil creep?

Answer 24

Slow down-slope movement of earth materials under the influence of gravitation.

Question 25

What is rock falls/ block falls?

Answer 25

This occurs on slopes >40’, where a rock fragment breaks away and either drops vertically (so it isn’t in contact with the cliff) or bounces downslope.

It’s initiated:
- By mechanical weathering
freeze-thaw
salt crystal growth
which breaks the cohesive bonds in the rock
- By marine erosion
Hydraulic action
Abrasion
Undercutting cliff by creating a wave-cut notch
Notch removed supporting material that supplied the resistive force holding up the rock

• Cliffs prone to block fall have:
  A geological structure with many joints, faults or bedding planes
  steep, near vertical dip of strata.
  They’re often also in earthquake-prone areas.

Blockfall is very rapid, taking only a few seconds to occur.

They may involve the detachment of single fragments or a whole cliff section that breaks up as it descends (which occurs by the undercutting of a wave-cut notch).

Question 26

What is rotational slumping?

Answer 26

• Rotational slumping involves rock failure and movement along a curved rock plane.
• The slumping material usually moves intact as a single mass, without any internal deformation of the material.
• It’s slower than block fall, often occurring in ‘slow motion’, and may take minutes, hours, days, or even years (for huge masses) to occur.
• Rotational slumping occurs in:
  ​weak rocks, e.g. clays and shales
  unconsolidated material, e.g. boulder clay, sands, gravels
  in rocks with complex geology, e.g. where permeable rock strata overlie impermeable beds
• Slumping is facilitated by the presence of water, which adds weight (increasing the gravitational force) as well as lubricating it, reducing friction.

Question 27

What is a landslide?

Answer 27

• A landslide is the downslope movement of discrete blocks of rock down a flat/linear slip plane, maintaining contact with the cliff surface throughout.
• The discrete blocks are released by mechanical weathering of well-jointed rocks, (e.g. carboniferous limestone). Gravity then pulls the loosened block down the relatively flat slip plane of the joint or bedding plane, to the cliff foot.
• Landslides can also be caused by marine erosion of a cliff foot undercutting blocks weakened by jointing. The removal of support allows gravity to release the block, resulting in sliding.
• Rainstorm events can encourage a landslide, lubricating the slip plane, and reducing the resistance.
• Landslides occur in consolidated rocks with joints or bedding planes sloping seawards.

Question 28

What are the 3 components of sediment cells?

Explain each one.

What is positive and negative feedback?

How many sediment cells are there in total and give examples?

Answer 28

Sources, sinks and transfers

Sources: Where sediment is generated. e.g cliff erosion, river transport.
Sinks: Locations where the dominant process is deposition and depositional landforms are created, including spits and offshore bars.
Transfers: Where sediment is moving alongshore through longshore drift and offshore currents. e/g swash, tides, backwash.

Positive feedback: Amplifies an impact.
Negative feedback: Reduces an impact.

The coastline of England and Wales is divided into 11 primary sediment cells.

Question 29

What is a geographical example of a source, sink and transfer?

Answer 29

Flamborough head: Source region

Holderness coast: Transfer region

Spurn Head: Sink region