2 Higher Coastal Landforms & Processes In this part of the course we will be looking at both:coastal erosionanddeposition.
3 Coastal Erosion We will be looking at the following: Waves our agent of erosionDifferent types of erosionLandforms of erosion
4 Coastal Deposition We will be looking at: a. Beach profiles (X sections) & WaveTypesb. Longshore Driftc. Landforms of deposition
5 Coastal ErosionTo start, we must recognise that waves are responsible for coastal erosion and that generally the bigger the wave, and the more frequent, the greater the erosion.This means that we will need to look at how waves form and differ in size. To do this we will look at Task 1 in your work book.
9 Wave ErosionThere are 3 ways that waves erode the coast. It is very important to describe and explain these as that will get you easy marks in an exam. You’ll need to show how they contribute towards the development of coastally eroded landforms. Watch the slides to find out more.
11 Air Compressed By Water Hydraulic PressureCrack In RockBreaking WaveAir Compressed By Water
12 Hydraulic Pressure Over time rock weakens and breaks off cliff Air explodes out of crack
13 Hydraulic Pressure Key words to describe hydraulic pressure. breaking waves ~ cliff ~ water ~ crackscompresses air ~ air explodes ~rock ~ time ~ breaks ~ force of water pounding ~ erodes ~ time
14 Waves carry rocks, shingle, sand CorrasionWaves carry rocks, shingle, sandRocks hit each otherRocks erode over time
15 Corrasion (abrasive) Key words to describe corrasion. broken rock ~ picked ~ wavesthrown ~ cliff faces ~ hard rock -erode ~ time
16 Small rocks rub against cliff AttritionWaves carry rocksSmall rocks rub against cliff
17 Key words to describe attrition. small rocks ~ H.P. ~ Corrasionwaves ~ rub ~ cliff ~ erosion
18 Corrosion A Fourth Type Of Erosion This is when the rock is broken down by chemicals in the sea such as salt. Rocks can either dissolve or rot and so start to crumble away. This is similar to solution in Limestone areas or the corrosion of stone carried in rivers.
19 Landforms Of Coastal Erosion We shall look at three principal types of landforms:i. Cliffs/Wave Cut Platformsii. Headlands/Baysiii.Headland Erosion (On Sides)
21 Cracks In rock are weak points Sea Cliff ErosionCracks In rock are weak pointsThese are eroded by waves at high tides by the 4 processes we’ve looked
22 Sea Cliff Erosion collapse of overhang cracks get larger & form a cave undercutting of cliff by cave
23 Repeated collapse over time Sea Cliff ErosionRepeated collapse over timeflat terrace remnant of base of cliff
24 Now do Task 3 Question 1 by filling in the key Sea Cliff ErosionNow do Task 3 Question 1 by filling in the key
25 W.C.P. exposed at low tide, but created at high tide Wave Cut PlatformW.C.P. exposed at low tide, but created at high tidefor later
26 Task 3 Question 2Waves ~ erosion ~ 4 types ~ name ~ general effect ~ high tideCracks ~ weak ~ widen ~ wave cut notch ~ cave ~ time ~ overhang ~ collapse of cliff (why) ~ repeats ~ retreatsBase of cliff ~ flat terrace ~ name it ~ exposed low tide
27 Headlands & Bays Task 4 large headland large bay small bay small headland
28 concordant parallel to sea Headlands & Baysconcordant parallel to seatwo typesdiscordant at 90º to sea
29 crack in rock eroded by waves Concordant Headlandscrack in rock eroded by wavessoft rockhard rockhard rock resists waves so narrow crack
30 Concordant HeadlandsBayHeadlandsoft rock erodes easily so wide bay
31 Discordant Headlands soft rock hard rock softer rocks erode more easily than harder ones ~ differential erosion
32 Discordant Headlands bay headland indents or bays form on the coast where the soft rock has receded
33 Task Question 3Geology ~ 2 key factors ~ (1) different rock types ~ hard ~ soft ~ side by side ~ (2) Layers 90º ~ seaWaves erode ~ hard rock ~ slow ~ resistant ~ soft rock ~ fast ~ soft indents ~ bays hard rock ~ sticks out ~ headlands
34 Headland Erosion (On Sides) These are a series of landforms developing one after the other on the side of a headland.
35 Caves/Blowholes/Arches/Stacks Label the sketch below in your work book using the word box for task 7.
37 Caves/Blowholes/Arches/Stacks 1 erosion on side of headlandwaves erode cracks into caves
38 Caves/Blowholes/Arches/Stacks 1 Cont. Explain sedimentary rocks easily exploited many cracksname your 3 types of erosion in exam
39 Caves/Blowholes/Arches/Stacks 2 blowhole in top of headlandwaves crash into back of cave and erode upwards into headland
40 Caves/Blowholes/Arches/Stacks 2 Cont. blowholes are relatively rarevertical cracks in rock help them to form
41 BlowholeRoof collapses due to erosion from waves splashing upwards from back of cave
42 Caves/Blowholes/Arches/Stacks 3 eventual break through to other side forms an archcontinued erosion of back of cave
43 Caves/Blowholes/Arches/Stacks 3 Cont. process can be sped up if cracks on other side being eroded
44 Caves/Blowholes/Arches/Stacks 4 little support so eventual collapse of rooffurther erosion sees widening of arch
45 Caves/Blowholes/Arches/Stacks 4 Cont. process can be aided by blowhole weakening roof
46 Caves/Blowholes/Arches/Stacks Now try and piece together the explanations for all of these landforms Task 7 question 2
47 Caves/Blowholes/Arches/Stacks 1) Waves crash into headlands eroding weaker parts such as cracks.2) The cracks are eroded by 3 different processes:- hydraulicpressure, corrasion & attrition. In an exam you should explain each of these!3) The crack starts to widen and form a cave, it can beundercut causing the roof to collapse due to lack of supportfor the roof. This helps the cave get larger.
48 Caves/Blowholes/Arches/Stacks 4) As the cave gets larger, waves start to hit into itsback wall and on impact are sent crashing into the roofof the cave where erosion occurs.5)The erosion of the cave roof can lead to a blowhole,where waves continue to erode upwards and through thetop of the headland. This is quite rare and needs a vertical crack line to be exploited (Sedimentary Rocks!).
49 Caves/Blowholes/Arches/Stacks 6) At the same time caves and blowholes develop, waveerosion can also lead to the development of an arch. This is when the cave erodes all the way through to the other side of the headland.7) There may be similar cracks on the other side of theheadland with erosion taking place, speeding up thedevelopment of the arch. Arches don’t necessary need blowholes to be present when they develop!
50 Caves/Blowholes/Arches/Stacks 8) Over time the waves continue to widen the walls of thearch leaving less support for the roof, leading to its collapse.This leaves a new headland on the landward side of the arch and the old wall still standing on the seaward side.9) this old wall is called a stack or a pillar and is also subjectto erosion by the sea. As it erodes it gets thinner at its baseand parts of it collapse leaving a narrower pillar called aneedle.
51 Coastal DepositionThis is essentially all about beaches and why they develop. We will look at:Swash & BackwashBeach ProfilesBeach Angle & Wave TypeLongshore DriftLandfroms Of Deposition
52 Why Beaches DevelopBeaches develop where material is deposited due to:Sheltered areas reducing wave velocityA large supply of sediment from eroded featuresLongshore Drift maintaining a beach