coasts ppt for year 11

8/17/2019 Coasts Ppt for Year 11

http://slidepdf.com/reader/full/coasts-ppt-for-year-11 1/62

COASTS



The coast is a narrow contact zone

between land and sea. It isconstantly changing due to theefects o land, air and marine

processes. The power o the waves the seacarries determines the type oprocesses that take place.



Wave Energy

1. Waves are created when wind blowsover the surace o the sea creatingriction.

. The size and energy o a wave variesaccording to its speed and theamount o time the wave has been

moving.

• Waves are biggest and have themost energy when the wind isstrong, has been blowing or a longtime and has come a long way.

• The distance over which a wave has

travelled is called fetch.!. "riction with the sea bed slows down

the bottom o the wave but the topo the wave continues moving at thesame rate and topples orward,braking against a clif or beach.

• Swash is water that washes up abeach



The size of the wave depends on…

• The strength of thewind.

• How long the wind blowsfor.

• The length of the waterthe wind blows over –called the fetch.

Extension: which waveswould be stronger? Why?

A: aribbean – !"#: $outh A%erica & Africa

A

B

#$oasts lesson % wave ormation



#rea'ing waves

• &s waves approachthe shore, thebottom o the wave

catches on the seabed ' causing thewave to build up(become taller).

The wave thenspills over (breaks)onto the beach.

(otice how the wave is )falling forward* – ithas built up and is brea'ing onto the shore.

*$oasts lesson % wave ormation

Extension: Tsunami+s are a

type o wave but are notcaused by wind. $an yousuggest what causes themLO1: I can describe how a wave



T"#ES O$ WA%E

There are two types o wave-

• $onstructive

• estructive



Constr&ctive

This wave haslimited energymost o this is used

by the swash totransport materialup the beach.



'estr&ctive

This wave hasmuch more energy./ost o this is used

by the backwash totransport materialback down thebeach.



0ot all waves are the same. The beachprole (shape o the beach) can be diferentdepending on how the waves break

Constr&ctive

• 2uild beaches.

/aterial is carried upthe beach in thestrong swash and isdeposited as thebackwash is weak '3ummer.

'estr&ctive

• estroy beaches. They

are very high andre4uent. Thebackwash is strongand transports beachmaterial out to sea 'Winter.

5

$oasts lesson % wave ormation

Extension: add 6beach prole+ toyour glossary with an accuratedenition.

LO(: I can identify the di)erences between constr&ctive and



$wash +s #ac'washSwash * oveent of water

&+ the beachBac,wash * oveent ofwater down the beach

Happens when the wave breaks:water rushes up the beach

Happens after the swash, when thewater is draining back into the sea.17

$oasts lesson % wave ormatio

Extension: 8ow might seasons afect theswash and backwash



The #each ,rofile

Constr&ctive 'estr&ctive

Gentle beaches are formed by

constructive waves.

Steep beaches are formed by

destructive waves. 11


Extension: name e9amples oplaces you might nd constructiveand destructive beach proles.

LO-: I can ex+.ain how di)erent waves can sha+e a variety



Which parts of the #ritish -sles willreceive the biggest waves and why?

Thin, abo&t the $ETC/0.ength of the water

Extension: Which +arts ofthe British Is.es wi.. receive

the sa..est waves andwhy2

he !epublic of "reland, and South#$est England %&ornwall' receive

the biggest waves as the fetch stretches across the (tlantic )cean.

$ e t c h

1


LO1: I can describe how a wave



Coasta. #rocesses

There are three main processes atwork in the sea-

:rosion

Transportation

eposition



Erosion

This is destructive waves wearing away the coastline. It happenswhen the waves are packed with energy. :rosion destroys landorms.

Waves erode in fo&r ways-

• /ydra&.ic action% Is when waves crash against clifs trapping and

compressing air and water in rock cracks. &s the waves move back,pressure is released causing the air and water to e9pand. Thise9plodes breaking of rock ragments.

• Abrasion%Is when breaking waves pound rocks and pebbles againstthe clifs wearing the land away in a sandpaper efect.

• Attrition%Is when waves smash rock ragments against each othermaking pebbles smoother, rounder and smaller. In time, the particlesare ground into grit and sand.

• Corrosion% Is when the chemicals in the sea water dissolve or rotrocks like limestone and chalk



What is coastal erosion % ;ouTube.mp#



The waves $O3CEwater into crac,s in

the roc,s!

This is ca..ed/"'3A4LIC

ACTIO5



This isca..ed

AB3ASIO5

The +ebb.esact .i,e

sand+a+er!

3o&gh seas 6ing+ebb.es against the

roc,s



The waves ,noc, ch&n,s of roc,together!

The roc,s end&+ as +ebb.eson the beach

This is ca..edATT3ITIO5



The water 'ISSOL%ES

so.&b.e ateria. frothe roc,s!This is ca..ed

SOL4TIO5

$ f t



he waves throw

sand, pebbles andlarge stones againstthe rock. hey wear

it away like sand

paper. his is calledabrasion.

he water dissolves

the rock. his iscalled solution.

&hunks of rock getknocked together

and worn into

smaller pieces. hisis called attrition.

$aves force waterinto cracks in therock, this pressurebreaks up the rock

# called hydraulicaction.



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CO#" T/E 'IA73A8 A5' A'' T/E CO33ECT LABEL$3O8 T/E $OLLOWI57:• 3eova. of stac, to create a st&+9• en.argeent of cave to for an arch9

• geo.ogica. wea,ness 0e!g fa&.t9• foration of sea cave by erosion9• co..a+se of arch to for st&+



Trans+ortation

Is the movement o material in the sea and along thecoast by waves.

• Transport along the coast is when waves move material

across a beach. This is long shore drit.• The prevailing wind causes the waves to break on the

beach at an angle

• 3wash carries the material up the beach at an angle.2ackwash drags the material back down the beach at right

angle.• :ach wave pushes material urther along the beach.

• /aterial is moved along the beach in the direction o theprevailing wind.



ransport *rocesses



ransport

*rocesses

+ongshore rift

raw an annotated diagra% to e/plain the process of longshoredrift.



'irection of+revai.ing wind

'irection of .ongshore driftoveent

swash

Bac,wash

Backwash isalways at rightangles to thebeach

>ongshore drit



Evidence forLS'



Which way is LS' oving sedient2



What is a storm beach



'e+osition

Is the dumping oeroded material onthe land by

constructivewaves. It happenswhen the waveshave less energy.

eposition createsland orms such asbeach,spit, marshand dune belts.



Beach

& beach is alandorm along theshoreline o an

ocean, sea, lake orriver. It usuallyconsists o looseparticles which are

oten composed orock, such as sand,gravel, shingle,pebbles or

cobblestones



S+it

& spit is ane9tended stretch obeach material that

only ?oins themainland at oneend. They start toorm where there is

a change in thedirection o thecoastline.



i



3tages o spitdevelopment-



Spits and salt marshes



Sa.t arsh

3alt marshes maybe ormed behind aspit. The zone

behind a spitbecomes asheltered area.Water movement

slows down and somore material isdeposited.eposition may

orm a salt marsh.



A sa.t arsh fors when incoing tides carry andde+osit sedient across .ow.ying .and; res&.ting in

wet &d6ats! Sa.twater grasses then s.ow.y ta,eho.d and s+read; stabi.ising the .and thro&gh thegrowth of root systes! As the +.ants decay andsedient b&i.ds &+; +eat de+osits acc&&.ate;

foring a rich habitat that s&++orts the growth of



Salt -arshes



They often deve.o+in the .ee 0she.tered+art of a s+it!



The sand dunes

at HengistburyHead are in the

early stages of

formation…

Sand unes

Sand une formation.



f

$hat you need is:



$actors which a)ect the s+eed that



$actors which a)ect the s+eed thatthe coast.ine is eroded:

. !ock type

/. $ave type

0. "f there1s a beach

2. Human activity

%pollution3walking'

4. 5egetation

ask: 0ist thesefactors which affectthe speed of coastal

erosion. 1or each2write one sentencee/plaining how this

affects erosionspeed.



These are sea stac's. -n groups of two write down a shortparagraph about how you thin' that they for%ed.



How do we protect the coast• To be able to e/plain how different types of coastal

defences wor'.• To be able to e/plain the advantages and the disadvantages

of all of the different %ethods of protection.

Coasta.8anageent



SEA WALLAbsorb wave energyso the c.i) foot is

+rotected froerosion



3i+ra+: @ip%rap is basically giantboulders placed at the oot (bottom) oclifs. @ip%rap is designed to absorb thewaves energy and protect the clifsbehind. @ip%rap can be efective, butdoes look ugly, may reduce access tothe beach and can be e9pensive.

@IA% @&A



7royne

s

Wooden ences built out into thesea. They stop long shore drit andbuild up the beach. & wide beachabsorbs more wave energy



3E%ET8E5T

They are similar to sea walls, but oten builtout o wood. Bten ound at the oot o clifsthey are designed to absorb the waveenergy. &gain they need replacing regularly

and do not protect against big storms.

CLI$$



CLI$$3E73A'I57

This means make clifs less steep. $lifsoten become unstable because oundercutting. 2y reducing the angle youshould reduce the undercutting and the

risk o the clif collapsing.

$lifs oten collapse because they



p ybecome saturated and theincreased stress causes them tocollapse. 2y removing some o thee9cess water you should reduce

stress on the clif.

Beach'rainage



BEAC/

$EE'I57

:9tra sediment is dumpedon the beach to increase itssize. & wider beach willabsorb more wave energy

and protect clif

How can the coastline be protected?



p

Hard engineering techniques aim to stop coastal processes

from occurring. Soft engineering methods try to work with

nature to protect the coast.

coasts ppt for year 11

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