Coasts

Question 1

Describe the negative feedback loop in a coastal environment?

Answer 1

1) Sediment is eroded during storm
2) Sediment is deposited offshore forming an offshore bar
3) Waves now break before reaching the beach, dissipating their energy and reducing further erosion
4) When the storm calms, normal waves conditions place the sediment in its original position.

Question 2

Name the inputs of a Coastal system ?

Answer 2

• energy from waves, winds, tides and sea currents
• sediment
  -geology of the coastline
  -sea level change

Question 3

Name the outputs of a Coastal system ?

Answer 3

• dissipation of wave energy
• accumulation of sediment above the tidal limit
• sediment removed beyond local sediment cells

Question 4

What is Backwash ?

Answer 4

The action of water receding back down the beach towards the sea.

Question 5

Key features of Constructive Waves ?

Answer 5

Waves with a low wave height, long wavelength and low frequency (6-8min). Swash tends to be more powerful than their backwash, therefore sediment builds up

Question 6

Key features of Destructive Waves ?

Answer 6

Waves with a high wave height, a steep form, a high frequency (10-14min). Their backwash is stronger than their swash, so more sediment is removed.

Question 7

Describe the process of wave refraction ?

Answer 7

High energy waves strike the headland. The waves are then refracted with a lower energy. Erosion is concentrated at the Headland. Deposition occurs at the bays.

Question 8

What is Longshore Drift ?

Answer 8

When waves hit the coastline at an angle. This creates a current which runs parallel to the shoreline, resulting in sediment to be transported along the coastline, in the direction of the prevailing wind.

Question 9

What are Rip Currents ?

Answer 9

These are strong currents moving away from the shoreline. These occur when seawater is piled up along the coastline before flowing into the breaker zone, where the coast direction changes. (dangerous for swimmers)

Question 10

What is Upwelling ?

Answer 10

The movement of cold water from the deep ocean towards the surface. This creates nutrient-rich cold ocean currents forming part of the global ocean circulation currents.

Question 11

What are tides ?

Answer 11

The periodic rise and fall of the level of the sea in response to the gravitational pull of the Sun and Moon.

Question 12

What are spring tides ?

Answer 12

Twice a year when the Moon, Sun and Earth are in a straight line, the tide raising force is strongest. Producing a spring tide.

Question 13

What is a Sediment Cell ?

Answer 13

A distinct area of coastline separated from other areas by well defined boundaries, such as headlands and stretches of deep water. There are 11 sediment cell in England and Wales.

Question 14

What is the Coastal Budget ?

Answer 14

Sediment is transferred across the sediment cell, through accretion or erosion.

Question 15

What are Marine Processes ?

Answer 15

Only operate onto a coastline and are connected with the sea, such as waves, tides and longshore drift.

Question 16

What are Sub-Aerial Processes ?

Answer 16

This includes processes that slowly break down the coastline, weaken the underlying rock and allow sudden movements or erosion to happen more easily. All of this occurs in situ. This includes weathering, mass movement and run-off.

Question 17

Examples of Marine Erosion ?

Answer 17

Hydraulic Action, Wave Quarrying, Abrasion, Attrition, Solution.

Question 18

What is the difference between a concordant and discordant coastline ?

Answer 18

Concordant coastline - one type resistant rock that protects the land from erosion. ( Dalmation Island, Croatia)
Discordant coastline - various types of rock face the coastline therefore weaker clays and gravel produce bays (Swanage Bay)[ bay and headlands ].

Question 19

Processes of Marine Transportation ?

Answer 19

Traction - large stones and boulders and rolled along the seabed.
Saltation - small stones bounces or leapfrog along the seabed.
Suspension - very small particles of sand and silt are carried along by the moving water.
Solution - dissolved materials are transported within the mass of moving water.

Question 20

What is Surface Creep ?

Answer 20

A process similar to traction, where wind rolls or slides sand grains along the surface.

Question 21

Examples of Mechanical / Physical Weathering ?

Answer 21

Freeze Thaw - water enters cracks in the rocks, freezes. As it freezes, the water expands by almost 10%. Exerting pressure on the rock, this processes repeats until pieces of the rock break off.
Pressure Release - As overlying material is removed, the rock beneath experiences a pressure release. The rock is now able to expand causing cracks and joints. Making it susceptible to erosion and weathering.

Question 22

Examples of Biological Weathering ?

Answer 22

These processes lead to the breakdown of rocks by the action of vegetation and coastal organisms.
-Marine organisms such as the piddock (shellfish) have specially adapted shells that enable them to drill into solid rock.
-Seaweed attaches itself to rocks and the action of the sea can be enough to cause swaying seaweed to prise away loose seabed.
-Some organisms, e.g. algae, secrete chemicals capable of promoting solution.
-Animals can weaken cliffs as they burrow or dig into them, such as rabbits or cliff nesting birds.

Question 23

Examples of Chemical Weathering ?

Answer 23

This occurs when rocks are exposed to air and moisture.
-solution
-oxidation causes rocks to disintegrate when the oxygen dissolved in water reacts with some rock minerals, forming oxides and hydroxides. It especially affects iron rich rocks and is evident when browning is visible on surface.
-Hydration addition of water to rocks, causing expansion and stress.
-Hydrolysis a mildly acidic water reacts with minerals to create weaker. (does not disintegrate rock!!)
-Carbonation
-Acid Rain

Question 24

Name the different types of Mass Movement ?

Answer 24

Landslides
Rock Falls
Mudflows
Rotation slip, or slumping

Question 25

What is a Swash Aligned beach ?

Answer 25

-Oriented parallel to the incoming wave crests.
-Experiences minimal longshore drift
-can be found on irregular coastlines where longshore drift is impressed, and waves hit sections of the coast head on.

Question 26

What is a Drift Aligned beach?

Answer 26

-Oriented parallel to the direction of the dominant longshore drift.
-develop on regular coastline and waves are at an angle to the beach.

Question 27

What is a Spit ?

Answer 27

Longshore drift moves material along the coastline in the direction of the prevailing wind. The angled swash brings material onshore, while the backwash removes the material in a straight line, perpendicular to the coastline.

This continues in a zig zag movement along the coast.

If the coast changes direction, material will continue to be deposited in the original direction in a shallow sea.

This build up of material is called a spit.

A spit needs a constant supply of material, or it will be removed by tides.

Over time, the spit grows and develops a hook if wind direction changes further out.

Waves cannot get past a spit, which creates a sheltered area where silt is deposited and mud flats or salt marshes form.

Longshore drift moves material along the coastline in the direction of the prevailing wind. The angled swash brings material onshore, while the backwash removes the material in a straight line, perpendicular to the coastline.

This continues in a zig zag movement along the coast.
If the coast changes direction, material will continue to be deposited in the original direction in a shallow sea.

This build up of material is called a spit.

A spit needs a constant supply of material, or it will be removed by tides.

Over time, the spit grows and develops a hook if wind direction changes further out.

Waves cannot get past a spit, which creates a sheltered area where silt is deposited and mud flats or salt marshes form.

Spurn Head, Holderness Coast

Question 28

What is a Tombolo ?

Answer 28

A spit that joins an island to the mainland. E.g. Chesil Beach UK

Question 29

What is Eustatic Change ?

Answer 29

A global change in sea level resulting from an actual fall or rise in the level of the sea itself.

Question 30

What are Rias ?

Answer 30

Rising sea levels drown river estuaries. The floodplain of a river will vanish beneath the rising water. This will deepen and widen the river

Question 31

Describe a coastal positive feedback loop ?

Answer 31

1. People walking over sand dunes destroys vegetation growing there and causes erosion.
2. As the roots from the vegetation have been holding the sand dunes together, damaging the vegetation makes the sand dunes more susceptible to erosion. This increases the rate of erosion.
3. Eventually the sand dunes will be completely eroded leaving more of the beach open to erosion taking the beach further away from its original state.

Question 32

What is the Littoral Zone ?

Answer 32

The littoral zone is the area of land between the ​cliff’s or dunes on the coast and the offshore area that is beyond the influence of the waves​. It is therefore covered by the sea at different points in time. The littoral zone is constantly changing because of:

● Short-term factors​ like tides and storm surges
● Long-term factors​ like changes in sea level and human intervention

Question 33

Describe a Salt Marsh succession

Answer 33

1. Algal Stage​ - Gut weed & Blue green algae establish as they can grow on bare mud, which their roots help to bind together.
2. Pioneer Stage​ - Cord grass & Glasswort grow, their roots begin to stabilise the mud allowing the estuarine to grow.
3. Establishment Stage​ - Salt marsh grass & Sea asters grow, creating a carpet of vegetation and so the height of the salt marsh increases.
4. Stabilisation​ - Sea thrift, Scurvy grass & Sea lavender grow, and so salt rarely ever gets submerged beneath the marsh.
5. Climax vegetation​ - Rush, Sedge & Red fescue grass grow since the salt marsh is only submerged one or twice a year.

Question 34

What is an Embryo Dune ?

Answer 34

Upper beach area where sand starts to accumulate around a small obstacle (driftwood, wooden peg, ridge of shingle)

Question 35

What is a Yellow Dune ?

Answer 35

As more sand accumulates and the dune grows, vegetation may develop on the upper and back dune surfaces, which stabilises the dune.

Question 36

What are Grey Dunes ?

Answer 36

Sand develops into soil with lots of moisture and nutrients, as vegetation dies, enabling more varied plant growth

Question 37

What is Dune Slack ?

Answer 37

The ​water table rises closer to the surface, or water is trapped between hollows between dunes during storms, allowing the development of moisture-loving plants (e.g. ​willow grass​)