Coasts 🌊

Question 1

Wave formation

Answer 1

Created by energy passing through water, causing it to move in a circular motion. However, water doesn’t travel in waves. Waves transmit energy, not water, across the ocean, they have potential to travel across an entire ocean basin. Waves are commonly caused by wind. As wind blows accross the surface of the ocean, the continual disturbance creates a wave crest. As the wave approaches the shore disturbance to the circular motion beneath the surface leads to more horizontal wave movement and the wave breaks.

Question 2

Destructive wave

Answer 2

Steep beach profile and caused cliff face erosion. Takes away material from the beach.

Question 3

Constructive

Answer 3

Adds materiel to beach through swash & backwash. Never reaches back of beach, strong swash, low wave with long wavelength.

Question 4

Tides

Answer 4

The periodic rise & fall in sea levels caused by the gravitational pull of the sun and moon. Both time and size of tides depend on a daily basis due to position of sun and moon relative to the earth. -Strength of wind = Bigger wave
-Small range = focussed erosion

Question 5

Spring tides

Answer 5

Occur twice each lunar month all year long without regard to season

Question 6

Neap tides

Answer 6

Occur twice a month but happen when sun and moon are at right angles to one another.

Question 7

“GAIA theory”

Answer 7

If we don’t have human interference, earth will be naturally recovered.

Question 8

Dynamic Equilibrium

Answer 8

A system in dynamic equilibrium has inputs & outputs of energy & matter that balance. Affected by the supply of sand, energy of the waves, sea level changes, location of the shoreline.

Question 9

Sources of energy at the coast

Answer 9

-wind: formed by air moving between areas if different pressure (from low-high) along a pressure gradient. Steeper gradient = faster wind moves = larger pressure & stronger winds.
-Initial energy at the coast is from sun. The wind generates waves from energy in different areas of pressure. Shown where some areas are more exposed than others.

Question 10

Earth sub-systems

Answer 10

Nutrient cycle, Carbon cycle, solar cycle, ocean circulation cycle, rock cycle, water cycle.

Question 11

Factors influencing the coastline

Answer 11

Marine processes: biotic features (eg reefs), waves shape/size, sea level change
Terrestrial processes: tectonics, supply of sediment, fluvial processes
Human intervention: sea defences, pollution, tourism & recreation, global warming, buildings
Atmospheric: winds, precipitation, temperature, sub-aerial processes

Question 12

Fetch

Answer 12

Distance of open water over which wind blows. The longer the fetch, the more powerful the waves. The longest fetch in the UK extends over 3000 miles from Brazil to the UK.

Question 13

Wave refraction

Answer 13

When waves approach a coastline that is not a regular shape, they are refracted and become increasingly parallel to the coastline. As each wave approaches the coast, it tends to drag in the shallow water which meets the headland, this increases wave height and wave steepness and shortens the wavelength. The part of the wave in deeper water moves faster, causing wave to bend. The overall effect is wave energy is more concentrated on the headland, causing greater erosion.

Question 14

Tidal range

Answer 14

Difference in height between the low & high tide marks, a large tidal range is important for providing energy via tidal currents and in transportation of sediment whilst a small tidal range is more important for concentrated erosion at the cliff base.

Question 15

Sediment cell

Answer 15

Stretch of coastline which sediment movement is contained. In total there are 11 cells around the UK, further dividing into sub-cell. Eg. Transfers (flows) or sinks (stores)- rivers, cliff erosion, offshore sediment, and wind are all sources of sediment.

Question 16

Offshore sediment

Answer 16

Can be transformed into the coastal (littoral) zones waves, tides, and currents. Eg. ‘Start Bay’ in Devon.

Question 17

Cliff erosion

Answer 17

Locally in areas of relatively soft/ unconsolidated rocks. Rate of erosion = 10m/year.

Question 18

High energy coastlines

Answer 18

Rocky coastline, erosion exceeds deposition, contains cliffs & headlands, many examples found in Cornwall.

Question 19

Low energy coastlines

Answer 19

Less powerful waves, sheltered areas (bays), beaches & spits found here, Sandy estuarine, deposition exceeds erosion

Question 20

Sand dunes

Answer 20

Depositional landform created by wind. We plant marsh grass or Lyme grass to help it grow. They act as a natural defence. Accumulations of sand are blown into mounds by the wind. Examples: embryo, fore, yellow, grey, dune slack & mature dune.

Question 21

Flocculation

Answer 21

Smaller particles (using clay) binding together & leading to deposition.

Question 22

Biological weathering

Answer 22

Breakdown of rocks by organic activity. Thin plants and animals burrowing can widen rocks & increase risk of chemical weathering.

Question 23

Chemical weathering

Answer 23

Human uses (CO2) oxidation reaction & carbonation.

Question 24

Mechanical weathering

Answer 24

Frost shattering (freeze thaw) water enters & freezes. Salt crystallisation occurs leaving salt crystals behind.

Question 25

River regime

Answer 25

Changes in currents & volume may affect erosion

Question 26

Marine geomorpholigical & sub-aerial processes

Answer 26

Marine (ocean): deposition, transportation (LSD), erosion. Sub-aerial (land): weathering, mass movement, runoff.

Question 27

Mudflows

Answer 27

Wet flow of mud downhill

Question 28

Soil creep/ solifluction

Answer 28

An extremely slow form of mass movement of individual soil particles downhill, wet movement.

Question 29

Run-off

Answer 29

Overland flow occurs, small particles moved downslope into the littoral zone, forming input into the sediment cell, occurs rapidly.

Question 30

Rockfall

Answer 30

Sudden collapse or breaking away of rock fragment at a cliff face. Dry fall occurs rapidly.

Question 31

Traction

Answer 31

Large particle-like boulders pushed along the sea bed by force of the water

Question 32

Suspension

Answer 32

Small particles like silt and clay are carried along the water.

Question 33

Solution

Answer 33

Soluble materials dissolve in water and are carried along

Question 34

Hydraulic action

Answer 34

Sheer force of water itself

Question 35

Wave quarrying

Answer 35

Compressed air into gaps causes huge pressure. Trapped air as wave hits cliff face. Air pressure released = explosive effects. Removes large chunks of rock in the process.

Question 36

Abrasion/ corrosion

Answer 36

Material thrown back thrown back and forth or against rock by waves.

Question 37

Attrition

Answer 37

Rocks worn down to be smaller and rounder.

Question 38

Submergence coastlines

Answer 38

Rise & fall of Uk & global sea level rise. See-saw effect of England, ecstatic rise.

Question 39

Emergence coastlines

Answer 39

Isostatic rebound. Also rise & fall of sea level rise.

Question 40

Isostatic

Answer 40

A global change in sea level resulting from a fall or rise in the level of the sea itself. Isostatic change show overtime land is moving up slowly.

Question 41

Eustatic

Answer 41

Local changes in sea level resulting from land rising & falling relative to the sea. Sea level change is eustatic, it’s due to two main factors: thermal expansion & land ice melt. -If all ice in green land melts = 7m sea level rise. Only 3 ice sheets in earth but contain the potential of 72m of global sea level rise.

Question 42

Bars

Answer 42

Ridges of sand are called offshore bars. A body of water cut off completely from open sea forms a lagoon behind the bar.

Question 43

SMP & ICZMs

Answer 43

Purpose of these is to avoid soft/hard engineering techniques being focussed on a single area often having an undesired effect in adjacent areas of coastline, involving stakeholders. More likely to be managed if it’s an area of outstanding beauty if famous. Coast needs managing for erosion, flooding and failure of former defences.

Question 44

Hold the line

Answer 44

Maintain current defences or build new ones to ensure coastline stays.

Question 45

Retreat the line

Answer 45

Allowing coastlines to retreat due to flooding & erosion but closely managed.

Question 46

Advance the line

Answer 46

Build new defences seaward of existing line

Question 47

Estuary

Answer 47

The point where the river meets the ocean (the mouth)

Question 48

Salt marsh

Answer 48

An area of coastal grass regularly flooded by seawater (a store) Succession in salt marshes: as tidal currents slowed they begin to deposit material, results in large amounts of biodiversity.

Question 49

Formation of a stack

Answer 49

When wave attack and sub-aerial weathering processes take place at the base and the top of the headland as wave refraction. As headland is being constantly attacked, cracks appear and form a cave as they increase in size, constant hit from either side hollow the cave out as an arch. Over time this will separate from the headland forming a stack and become a stump as base is frequently eroded. Eg. “Old Harry (stack) & his wife (stump)”.

Question 50

Wave-cut platforms

Answer 50

Waves breaking at the foot of a cliff produce a wave-cut-notch. Undercutting results in erosion by waves eg. Abrasion etc.. As cliff is undercut, the rock above collapses and so the cliff gradually retreats. A wave-cut platform is left behind where the cliff used to be. This is covered during high tide.

Question 51

Spits

Answer 51

Long narrow feature extending from mainland.

Question 52

Tombolos

Answer 52

They join the mainland to an offshore island via deposition.

Question 53

Factors affecting rate of erosion

Answer 53

Wave power/ speed, constructive/destructive wave, magnitude (size), tidal range (small/large), wind speed (LSD), rock type (hard-slower rate eg.limestone) (soft- faster rate eg.clay), human defences (eg. Sea defences), types of weathering, plant activity, temp/pressure.

Question 54

Concordant coastlines

Answer 54

Rocks on these coastlines run parallel to the sea (present in South Purbeck)

Question 55

Cliff profiles

Answer 55

Refers to how steep the cliff face is at its meeting point with the sea.

Question 56

Beaches

Answer 56

Most common depositional landform, ranging from a few meters in less or a few hundred km.

Question 57

Swash aligned

Answer 57

Waves normally approach at 90 degrees to the beach, no LSD, roughly symmetrical shape

Question 58

Drift aligned

Answer 58

Asymmetrical, LSD, changes along the beach.

Question 59

Discordant coastline

Answer 59

Rocks on these coastlines run perpendicular to the sea (present in East Purbeck)

Question 60

Tectonics (& set amount of water on earth)

Answer 60

Triassic - 200 million years ago Jurassic - 145 million years ago Cretaceous - 65 million years ago Permian - 250 million years ago

Question 61

Causes of change in coastal system [hint: there’s 2 specific causes of change]

Answer 61

1) Water volume: changes due to thermal expansion (gets larger when hot) or addition of extra water from land stores (ice melt) 2) Subsistence: coastal areas sinking often due to excess ground water extraction. Has effect of making sea level (relatively) higher

Question 62

Positive feedback

Answer 62

Effects of an action are amplified by changes to inputs/outputs/processes.

Question 63

Negative feedback

Answer 63

Effects of an action are nullified by changes to inputs/outputs/processes.

Question 64

Emergent coastal landform=

Answer 64

Raised beaches: land rose as a result of Isostatic recovery; common in west coast of Scotland.

Question 65

Submergence coastal landform:

Answer 65

Dalmatian coasts: form in landscape of ridges & valleys & becomes flooded & submerged.

Question 66

Sediment budgets

Answer 66

Material in a sediment cell can be considered in form of sediment budget (where losses & gains occur). Losses = deposition in sediment sinks, whereas gains = coastal erosion or sediment brought into the system by rivers or offshore sources. Budget seeks dynamic equilibrium. A severe storm may upset balance by eroding beach and transferring sediment outside the system.

Question 67

Coastal Morphology

Answer 67

Related to the underlying geology (rock type) but also its lithology (geographical structure).

Question 68

Strata

Answer 68

Layers of rock

Question 69

Bedding planes

Answer 69

Horizontal, natural breaks in Strata, caused by gaps in time during periods of rock formation.

Question 70

Joints

Answer 70

Vertical structures caused by contractions as sediments dry out or by earth movements during uplift.

Question 71

Folds

Answer 71

Formed by pressure during tectonic activity, which makes rock buckle and crumble.

Question 72

Faults

Answer 72

Formed when stress or pressure to which a rock is subject exceeds its internal strength (causing it to fracture). The faults then slip or move.

Question 73

Dip

Answer 73

Refers to an angle at which rock strata lie (horizontally, vertically, dipping towards sea, or dipping inland).

Question 74

Human intervention at coast

Answer 74

According to the UN nations environment programme (UNEP) about 1/2 the world’s population live within 60km of coastline. In addition 3/4 of all cities are coastal. Traditional approaches to coastal management = direct action (hard & soft engineering) focussing on relatively short stretches of coastline intended to reduce erosion or flooding risk.

Question 75

Hard engineering

Answer 75

- Sea walls: concrete/stone walls at foot of a cliff, usually have a curved face to reflect waves back to the sea. Adv: effective, usually have walkway for people to walk. DisA: unnatural look, expensive to build and maintain. - Gyrones: Timber/rock structures built at right angles to the coast. They trap sediment being moved along the coast by LSD- building up the beach. Adv: works with natural processes to build up the beach. DisA: starve beaches further along coast of fresh sediment unnatural and unattractive. - Rip-Rap: (rock armour), large rock at foot of cliff or top of beach. Permeable barrier (only some water can pass, breaks up waves). Adv: cheap & easy to construct. DisA: intrusive. Rocks used are usually not local and can look out of place with local geology.

Question 76

Soft engineering

Answer 76

-Cliff regrading & drainage: reduces angle of cliff to help stabilise it. Drainage removes water to prevent landslides & slumping. Adv: can be effective in clay or loose rock where other methods don’t work. Drainage cost is effective. DisA: causes cliff to retreat. Drained cliffs can dry out & lead to rock collapse. -Beach nourishment: adding sand to beaches. Adv: cheap & easy to maintain. Looks natural & attracts tourists. DisA: Needs constant maintenance because of erosion & LSD.

Question 77

Sources of sediment

Answer 77

-Rivers: sediment transported in rivers accounts for majority of coastal sediment (esp. in high rainfall environments, where river erosion occurs). This sediment will be deposited in river mouths, & estuaries & reworked by wave tides/currents. -cliff erosion: important in areas of relatively soft/unconsolidated rock. -offshore sediment -wind: in glacial/hot environments, wind-blown sand can be deposited in coastal regions.

Question 78

The holderness coastal system

Answer 78

Main input is erosion of weak & unconsolidated cliffs. Eg. Flamborough head in the north or Spurn head.