Enquiry 2 how do characteristic coastal landforms contribute to coastal landscapes

Question 1

waves

Answer 1

caused by friction between wind and water transferring energy from the wind into the water
force of wind generates ripples
in open sea:
-waves simply energy moving through water
-water itself only moves up and down
-some orbital water particle motion within the wave, but no net forward water particle motion

Question 2

wave size depends on

Answer 2

strength of wind
duration wind blows for
water depth
water fetch

Question 3

waves break as water depth shallows towards the coastline

Answer 3

• wave depth of half the wavelength, internal orbital motion of water within wave touches sea-bed
• creates friction between wave and sea bed= slows down
• wavelength decreases and wave height increases=’bunch’ together
• wave crest move forward much faster than trough
• wave crest outruns trough and wave topples forward

Question 4

constructive

Answer 4

low wave height (1m) and long wavelength (100m)
‘flat’ waves with strong swash and weak backwash
strong swash push sediment up beach and deposits at ridge of sediment (berm)

Question 5

Destructive

Answer 5

13-15 minute frequency 
Remove sediment 
Height over 1m
Length 20m
Stronger backwash than swash
Crest forward and downward = air pocket 
Erodes beach material and carries it offshore= offshore ridge or bar

Question 6

Beaches have landforms that constantly change

Answer 6

Storm beaches- high at back of beach
Results from high energy deposition of very coarse sediment during severe

Berm ridges- typically of shingle/gravel result from summer swell wave deposition

Low channels and runnels between berms

Offshore ridges/ bars formed by destructive wave erosion and subsequent deposition of sand and shingle offshore

Question 7

Hydraulic action

Answer 7

Hydraulic action (wave quarrying)- air trapped in cracks and fissures is compressed by the force of waves crashing against cliff face

Pressure force crack open

More air trapped and greater force experienced in next cycle of compression

Dislodges blocks of rock from cliff face

Question 8

Abrasion (corrosion)

Answer 8

Sediment picked up by breaking waves thrown against cliff face

sediment chisels surface and wears it down

Question 9

Attrition

Answer 9

Sediment moved by waves

Collisions chip fragments

Sediment smaller and rounded

Question 10

Corrosion (solution)

Answer 10

Carbonate rocks vulnerable to solution by rainwater, spray from sea and seawater

Question 11

Erosion coastal landforms

Answer 11

Wave cut notch

Eroded at has if cliff by hydraulic action and abrasion

Notch becomes deeper

Over hanging rock become unstable and collapses as rock fall

Repeated cycle of notch cutting and collapse = recede

Former cliff position shown by horizontal rock platform visible at low tide = wave cut platform

Question 12

Sediment transport and deposition

Answer 12

Sediment transport processes

Traction- sediment rolls along pushed by currents = pebbles, cobbles, boulders

Saltation- sediment bounces along( force of water/wind) = sand sized particles

Suspension- sediment carried on water column (suit and clay particles)

Solution- dissolved material carried in water as solution (chemical compounds in solution)

Question 13

Long shore drift

Answer 13

Net transport of sediment along the beach as a result of sediment transport in the swash and backwash

Most coastlines there is dominant prevailing winds so over time there is dominant direction of LSD

Question 14

Deposition occurs in two main ways

Answer 14

Gravity settling- energy transporting water becomes too low to move sediment

Large sediment deposited first

Flocculation- small particles remain suspended in water. Clay particles clump together through electrical or chemical attraction and become large enough to sink

Question 15

Spit (depositional landform)

Answer 15

Sand/shingle beach ridge extending beyond turn in coastline

Usually greater than 30 degrees

At turn, LSD current spreads out and loses energy

Leads to deposition

Length determined by existence of secondary currents causing erosion (flow river or wave action) which limits strength

Question 16

Bayhead beach

Answer 16

Waves break at 90 degrees to shoreline

Move sediment into a bay where beach forms

Through Wave refraction, erosion is concentrated at headlands and bay is are of deposition

Question 17

Tombolo

Answer 17

Sand or shingle bar links coastline to offshore island

Result of wave refraction around offshore island

Creates area of calm water and deposition between island and coast

Opposing longshore currents may play role

In which case depositional feature is similar to spit

Question 18

Barrier beach/ bar

Answer 18

Sand/shingle beach connecting two areas of land

Shallow water lagoon behind

Features form when spit grows so long that it extends across bay, closing it off

Question 19

Vegetation

Answer 19

Important role in stabilising depositional landforms

Plant succession bonds loose sediment together and encourages further deposition

Question 20

Three interlinked components of sediment cells

Answer 20

Sinks- locations when dominant process is deposition and depositional landforms created (spits/offshore bars)

Transfer zones- sediment moving along shore through LSD and offshore currents( beaches and parts of dunes and salt marshes perform function)

Sources- sediment is generated (cliffs/ eroding sand dunes) some sources= offshore bars and river systems (important source for coast)

Question 21

Natural conditions for sediment cells

Answer 21

Inputs/ outputs/ transfers of sediment

Operate in state of dynamic equilibrium

Question 22

Negative feedback mechanisms help maintain balance by pushing system back towards balance

Answer 22

1. During major erosion a large amount of cliff collapse may occur

Rock debris at base of cliff will slow down erosion by protecting cliff base from wave attack

2. Major erosion of sand dunes lead to excessive deposition of offshore, create offshore bar that reduces wave energy allowing dunes time to recover

Question 23

Disrupted cell

Answer 23

Defences interrupt cliff erosion

Groynes trap LSD (transfers stop)

River straightening slows sediment input

Question 24

Positive feedback leads to disequilibrium in sediment cell

Answer 24

Increased storminess- lead to long term erosion of sand dunes and no chance to recover between events

Rising sea levels- could increase spit/ estuary erosion which removes sediment faster than replaced

Question 25

Weathering

Answer 25

The in situ breakdown of rocks by chemical, mechanical of biological agents (don’t involve any movement)

Subaerial process

Question 26

Mechanical weathering

Answer 26

Breaks down rocks by exertion of physical force and don’t involve Chemical change

Question 27

Chemical weathering

Answer 27

Chemical reaction and generation of chemical compounds

Question 28

Biological weathering

Answer 28

Speeds up mechanical and chemical weathering through action of plants, bacteria or animals

Question 29

Iithology

Answer 29

Different rock types

Question 30

Mechanical weathering

Answer 30

Freeze thaw- water expands by 9% in volume when freezes, exerts force within cracks/ fissures = loosed rocks

Vulnerable rocks- any with cracks/ fissures especially high on cliffs away from salt spray

Salt crystallisation- growth of salt crystals in cracks and pore spaces can exert breaking force

Vulnerable rocks- proud and fractures (sandstone) and effect is greater in hot dry climates (prompts evaporation and precip of salt crystals)

Question 31

Chemical weathering

Answer 31

Carbonation- slow dissolution of limestone due to rainfall producing calcium biocarbonate in solution (limestone)

Hydrolysis- breakdown of minerals to form new clay materials due to effect of water and dissolved Carbon dioxide (igneous and metamorphic containing feldspar)

Oxidation- Addition of oxygen to minerals especially iron compounds which produces iron oxide sand increases volume (sandstones)

Question 32

Biological weathering

Answer 32

Plant roots- roots growing in cracks and fissures forcing rocks apart (important process on vegetated cliff tops which contribute to rock fall)

Rock boring- species of clams that bore into rock and may secrete chemicals that dissolve rocks (sedimentary rocks especially carbonate rocks in inter tidal zones)

Question 33

Weathering contributes to coastal recession in number of ways

Answer 33

Weakens rocks making them more vulnerable to erosion of mass movement processes

Some strata may be more vulnerable to weathering than others

Contributes to formation of wave cut notches and effects overall cliff stability

Rates are v slow

Even hot wet climate , basalt 1-2mm every 1000 years

Question 34

Mass movement

Answer 34

Downslope movement of rock and soil.

Includes landslides/ rockfall/ rotational slide

Some coastlines it’s the dominant process

Classified by how rapid movement is and type of material

Question 35

Fall

Answer 35

Rock/block falls rapid form of mass movement

Blocks of rock can be dislodged by mechanical weathering/ hydraulic action

Undercutting of cliffs by wave cut notches can lead to large falls and talus scree slopes at base

Question 36

Topple

Answer 36

Geological structure influences topples

Very steep seaward dip rock strata

Undercutting by erosion lead to instability and blocks of material toppling seaward

Question 37

Rotational slide/ slumping

Answer 37

Mass movements can occur along a curved failure surface

Hide masses of material slowly rotate downslope over periods (days to years)

Water plays important role

Back-scar and terraced cliff profile

Question 38

Flow

Answer 38

Common in weak rocks (clay)

Become saturated and lose cohesion and slow downslope

Heavy rainfall combined with high waves and tides contribute to saturation