Geography: Coasts

A place at which land meets the sea

The break down of rocks at earths surface by rain water, temperature, biological, chemical and physical activity

Roots from plants find a way into gaps in rock and weaken as gaps expand and widen so pieces fall off

Animal burrowing and walking over surface can wear away and weaken surface so prices fall away

Wind can blow small grains of sand against rock and wear it away

Rain and waves hit rock - wear it away

What expands when it freezes, so water enters cracks and freezes, the crack expands and when ice melts it can get further in crack and freeze and melt and so on until crack is so big the rock is to weak so it falls off

Reactions break down bonds holding rock together so they fall apart

More common in location with a lot of water as it is needed for for chemicals to reach the rock

When oxygen combines with other elements to make another type of rock, it’s broken down Becuase it’s become softer

When water combines with substances in rock to form new substances which are softer than original rock

Carbon Dioxide reacts with rock to become a solution and is carried away

Types of mass movements

They occur on steep cliffs that have been weakened by weathering

The saturated mass falls down along a distinct SLIP PLANE which is likely a fault

Occur after heavy rain

Where a large amount of rock slides down the cliff, it happens along a fairly straight slip plane- something along natural plane in rock

Rocks prone to freeze thaw weathering result in falling rocks losing contact with cliff face
Need a vertical cliff and seasonal climates

At bottom of cliff they land and fan out to form a SCREE SLOPD

Soft rock saturates permeable surface but stops at impermeable surface beneath, the saturated rock slips along curved plane towards beach

Happens again as waves undercut cliff base do its unstable and slumps

Downslope movement of rock or mud and soil under influence of gravity

Heavy rain usually triggers it

Scale of movement is determined by extent of weathering

A body of water moving towards the coastline at a higher than average level

First there is a circular orbit in open water

Friction with seabed sorrows the circular orbital motion

There’s an increasing elliptical orbit at the top of wave moves faster

Wave begins to break

Then hits beach

ALWAYS AT RIGHT ANGLE TO SEA its water from a wave that returns

Water that rushes up the beach and goes up at angle of the wind

High wave in proportion to length

A tall wave breaks downwards with great force near Beach

Long fetch

Short wavelength

Strong backwash

Weak swash

Created in storm conditions

Tend to erode coast

Low wave in proportion to length

Strong swash

weak backwash

Long wavelength

Created in calm weather

Break at shore and deposit material to build up beaches

Distance wing travels to create a wave

Break down and removal of rock

Rates of weathering

Power of backwash

Location

Fetch length

Rock type/resistance

Direction of wing

Shape of coastline

Human intervention

Material carried by waves bump info eachother and are smoothed and broken down into smaller pieces

Waves enter cracks (faults ) in coastline and compress air within crack
When wave retreats the wake expands causing a minor explosion

Chemical action of sea water, acids in salt water dissolve rocks on the coast

Limestone and chalk prone to it

This is a process where coast worn down by matieral carried by waves hit the rock sometimes at high velocity

Area of resistant rock which protude (stick out) from coastline

Area of soft rock between 2 headlands that erodes quickly

When there's is variation in rock type the softer rock erodes faster and over hundreds of years a bay is formed

Coves due to rock type changing parallel to sea

Bays due to variation so bands of rock meet at a right angle to sea

Waves break on cliff face and erode

Erosion continues between high and low water mark and undercut(called a wave cut notch) rest of cliff face over hundreds of years

The notch becomes deeper and wider and overhand formed

The overhand collapsed and cliff retreats leaving a wave cut platform (bur of rock at bottom of cliff face)

Lines of weakness in headland form form erosion

Continues to form a small sea cave

Over hundreds of year it deepens and widens to make a cave

Cave erodes back and breaks through other side forming an arch

Weathering breaks down roof of arch and collapsed leaving stack

Erosion weakens it to form a stump as it collapsed

Waves are caused by wind the direction the waves travels depends on sing direction

The direction most win travels in is prevailing wind - it's south westerly in uk

Pebbles and larger sediment rolled along sea bed

Load bouncing/hopping along the sea bed eg small pieces of shingle

Small particles eg silts are carried in water which make it appear cloudy

Dissolved chemicals in sea water carried in solution - not visible

The transport of sediment along a stretch of coastline caused by waves approaching the beach at an angle that's not 90 degrees

When a wave enters shallow water

Waves enter a sheltered area eg a cover or bay

There's little wind

There is a good supply of material

Wide expanse of beach so swash expands out and weakens waves - weaker backwash

Formed by deposition

A beach is a gently sloping area of land between the high and low water marks

Beaches are no permanent they are altered by waves

Material at mouth of rivers

Cliff erosion

Lines to show concentrations of wave energy in wave refraction

As waves approach the coast they are refracted so that their energy is concentrated around headlands(shallow water) but reduced around bays. Waves tend to approach the coastline parallel to it, their energy decreases as water depth increases

Sandy and pebble

Sometime is has sand dunes behind it

Very gently sloping - almost flat

Formed by generally constructive waves

At low tide water filled depressions called tunnels form

Storm beach with large pebbles at the back of it

Pebbles get generally larger towards the back of the beach

Generally quite steep

Don't stretch far inland

Formed largely by powerful destructive waves

Offshore, nearshore, foreshore, backshore, coastal terrain

Destructive waves drag beach depositors offshore from berms or sand dunes: forming an offshore bar- lowers height of beach

Waves are not breaking

This is where waves breaks

Inter tidal zone that is covered then uncovered by changing tides - where sea hits sand

Not usually affected by waves so usually dry

Berms form

Dunes or storm beach

cliffs or plain too

Rarely affected by waves

Terrace in backshore, above the water level at high tide, formed in calm weather when constructive waves transport material

A spit is a finger of land made of sand and shingle thag extends into the sea from a coastline

Longshore drift carries sediment along the coast, the swash is how the material is carried up the beach and the backwash takes it back down, in this way material is moved along the coast in the direction of the prevailing wind. If the coast changes direction then sediment is continued to be dropped in original direction. In this way a long ridge of material is deposited - this is a spit. Further out to sea the end of the spit it often curved due to waves approaching from a different direction

Longshore drift caused by prevailing wind deposits material in that direction

When there is a bay - LSD direction does not change and so form a spit to enclose the bay from headland to headland leaving a lagoon

On the backshore of the beach

Large flat beach - wind can blow sand across beach

Large supply of sand - needed to build up sand dune

Onshore Wind - needed so material can be pushed into beach

Large tidal range - allows sand to dry out to be blown by wind

Obstacle such as drift wood
Sand hits obstacle and so sand can build up around it

Large material rolled along beach surface

Small material bounced along surface by wind

Smaller/ fine sand and material carried in wind

At back of beach there's an obstacle eg drift wood
The heaviest grains settle against obstacle and lighter ones on other side
Side facing wind begins to form a crest
Because the pile of sand is too steep to build up the crest collapses under own weight
Sand stops slipping at a gradient of 30-34 degrees
Sand dunes migrate inland as repeated movement of material up windward side and down leeward side
Sand dune itself becomes and obstacle so others form In front of it

Embryo dune

Fore dune

Yellow dune

Grey dune

Mature dunes

Where bands of different rock types run parralel to coastline

Layers of rock run at right angles to coa

Swanage bay

Christchurch bay

Pool bay

Stud land bay

Lulworth cove

Durlston head

Ballard point

Broad bench beach

Durdle door

Seacombe cliff

Canford cliff

Sandbanks

Hurst spit

Keyhaven salt marsh

A line of weakness in a hard rock eg Portland stone allowed water through
Behind this hard concordant layer, soft rock allows erosion
Over time cove widens due to lateral erosion but neck stays quite narrow
When is reached a hard rock at back of cove, erosion is slowed and lateral erosion of soft rock continues

Do nothing - let sea undertake natural processes

Hold the line- build protection st the current cliff face to prevent further damage

Advance the line - build defences aimed at reclaiming small areas of land to assist with protection

Managed retreats - allow some managed loss

Designed to build up material on one side to prevent it being moved by LSD

Starved material downwind of material
Life span 20-30 years
Relatively cheap £5000 each
Cause barrier for pedestrians

Large boulders piled along shoreline to form a sea wall

Allows some water through to disperse energy but reduces erosion of cliffs

Must be large strong rocks eg granite or basalt with are expensive
Quick to build

Natural looking

Sand added to replace sand washed away

Absorb wave energy so it can't reach cliffs to erode it

Must be replaced regularly
Natural appearance
Little environmental impact

Large steel mesh cages filled with Rocks at right angles to coastline

Absorb wave energy
Cheap £110 a metre
Only work on sandy beaches (pebbles would break them down)

Can be hazardous if not replaced when needed

Concrete walls built to protect coast from erosion
Stops waves hitting coastline

Seen as ugly
Gives tourists place to walk
If poorly maintained could collspse leading to damage

Artificial creation of dunes

Can take several heart for dunes to be established

Must provide walkways to avoid trampling

Cheap £2000 per 100m stretch

Improved coastal Eco systems

Natural and appealing

Creating a man made position for coastline - generally moving coast inland

Less chance of area flooding somewhere else

Long term sustainable

Less money spent on other problems

Can disrupt other area

Compensation for land and housing being destroyed a lot

Very expensive eg medmerry land £28 million

Material moved back by a storm is brought forward to protect areas behind

Expensive £200,000 a year due to time and equipment

Can seem artificial looking as high crest

No new material needed to be bought just added

Tourism £472.8 a year

Toursism employs 11,600

3000 homes at erosion risk

100 businessss at erosion risk

Tourist board

Bournemouth council

People further down coast

Environmental groups

Bournemouth locals

Developers eg builders