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Higher Coasts Lithosphere. Higher Coastal Landforms & Processes In this part of the course we will be looking at both: coastal erosion and deposition.

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Presentation on theme: "Higher Coasts Lithosphere. Higher Coastal Landforms & Processes In this part of the course we will be looking at both: coastal erosion and deposition."— Presentation transcript:

1 Higher Coasts Lithosphere

2 Higher Coastal Landforms & Processes In this part of the course we will be looking at both: coastal erosion and deposition.

3 Coastal Erosion We will be looking at the following: 1)Waves our agent of erosion 2) Different types of erosion 3) Landforms of erosion

4 Coastal Deposition We will be looking at: a. Beach profiles (X sections) & WaveTypes b. Longshore Drift c. Landforms of deposition

5 Coastal Erosion To 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.

6 Fetch = Distance + Wind

7 Coastal Erosion Now for Task 2 all about waves actually breaking down rock, or erosion.

8 Crashing Waves Erode Land

9 Wave Erosion There 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.

10 The Three Main Types Of Erosion

11 Hydraulic Pressure Breaking Wave Crack In Rock Air Compressed By Water

12 Hydraulic Pressure Air explodes out of crack Over time rock weakens and breaks off cliff

13 Hydraulic Pressure Key words to describe hydraulic pressure. breaking waves ~ cliff ~ water ~ cracks compresses air ~ air explodes ~ rock ~ time ~ breaks ~ force of water pounding ~ erodes ~ time

14 Corrasion Waves carry rocks, shingle, sand Rocks hit each other Rocks erode over time

15 Corrasion (abrasive) Key words to describe corrasion. broken rock ~ picked ~ waves thrown ~ cliff faces ~ hard rock - erode ~ time

16 Attrition Small rocks rub against cliff Waves carry rocks

17 Attrition Key words to describe attrition. small rocks ~ H.P. ~ Corrasion waves ~ 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 Platforms ii. Headlands/Bays iii.Headland Erosion (On Sides)

20 sea cliff erosion wave cut platform Sea Cliff Erosion Wave Cut Platforms (Task 3)

21 Sea Cliff Erosion Cracks In rock are weak points These are eroded by waves at high tides by the 4 processes we’ve looked

22 Sea Cliff Erosion cracks get larger & form a cave undercutting of cliff by cave collapse of overhang

23 Sea Cliff Erosion Repeated collapse over time flat terrace remnant of base of cliff

24 Sea Cliff Erosion Now do Task 3 Question 1 by filling in the key

25 Wave Cut Platform for later W.C.P. exposed at low tide, but created at high tide

26 Task 3 Question 2 1)Waves ~ erosion ~ 4 types ~ name ~ general effect ~ high tide 2) Cracks ~ weak ~ widen ~ wave cut notch ~ cave ~ time ~ overhang ~ collapse of cliff (why) ~ repeats ~ retreats 3)Base of cliff ~ flat terrace ~ name it ~ exposed low tide

27 Headlands & Bays Task 4 large headland small headland large bay small bay

28 Headlands & Bays two types concordant parallel to sea discordant at 90º to sea

29 Concordant Headlands crack in rock eroded by waves soft rock hard rock hard rock resists waves so narrow crack

30 Concordant Headlands Bay Headland soft rock erodes easily so wide bay

31 Discordant Headlands soft rockhard 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 3 1)Geology ~ 2 key factors ~ (1) different rock types ~ hard ~ soft ~ side by side ~ (2) Layers 90º ~ sea 2)Waves 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.

36 Caves/Blowholes/Arches/Stacks cavewave cut platform blowhole arch stack needle

37 Caves/Blowholes/Arches/Stacks 1 erosion on side of headland waves erode cracks into caves

38 Caves/Blowholes/Arches/Stacks 1 Cont. name your 3 types of erosion in exam Explain sedimentary rocks easily exploited many cracks

39 Caves/Blowholes/Arches/Stacks 2 blowhole in top of headland waves crash into back of cave and erode upwards into headland

40 Caves/Blowholes/Arches/Stacks 2 Cont. blowholes are relatively rare vertical cracks in rock help them to form

41 Blowhole Roof collapses due to erosion from waves splashing upwards from back of cave

42 Caves/Blowholes/Arches/Stacks 3 continued erosion of back of cave eventual break through to other side forms an arch

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 further erosion sees widening of arch little support so eventual collapse of roof

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:- hydraulic pressure, corrasion & attrition. In an exam you should explain each of these! 3) The crack starts to widen and form a cave, it can be undercut causing the roof to collapse due to lack of support for the roof. This helps the cave get larger.

48 Caves/Blowholes/Arches/Stacks 4) As the cave gets larger, waves start to hit into its back wall and on impact are sent crashing into the roof of 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 the top 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, wave erosion 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 the headland with erosion taking place, speeding up the development of the arch. Arches don’t necessary need blow holes to be present when they develop!

50 Caves/Blowholes/Arches/Stacks 8) Over time the waves continue to widen the walls of the arch 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 subject to erosion by the sea. As it erodes it gets thinner at its base and parts of it collapse leaving a narrower pillar called a needle.

51 Coastal Deposition This is essentially all about beaches and why they develop. We will look at: 1)Swash & Backwash 2)Beach Profiles 3)Beach Angle & Wave Type 4)Longshore Drift 5)Landfroms Of Deposition

52 Why Beaches Develop Beaches develop where material is deposited due to: 1)Sheltered areas reducing wave velocity 2)A large supply of sediment from eroded features 3)Longshore Drift maintaining a beach

53 Swash & Backwash swashbackwash

54 Swash & Backwash water swashing up a beach

55 Why Beaches Develop Swash & Backwash Task 8 Backwash Swash

56 Gentle Beach Constructive Waves circular elliptical strong swash weak backwash

57 Gentle Beach Constructive Waves Now for Task 9 Question 1 Complete the passage using the word box

58 Steep Beach Destructive Waves strong backwash weak swash circular wave elliptical wave rotation of wave

59 Steep Beach Destructive Waves Now for Task 9 Question 2 wave ~ friction ~ seabed ~ elliptical ~ just before breaking ~ steep wave ~ rotates back ~ weak swash ~ strong backwash ~ sediment lost ~ destructive wave

60 Longshore Drift breaking swash breaks at angle on beach

61 Longshore Drift Swash loses energy & backwash returns straight down beach due to gravity

62 Longshore Drift Zigzag movement of sediment with swash & backwash means sediment moved along beach

63 Longshore Drift swashbackwash direction of longshore drift moving sediment

64 Longshore Drift Explaining longshore drift Task 10 swash angle ~ energy loss ~ backwash ~ gravity ~ straight down ~ carries sediment ~ up ~ down ~ along beach

65 Landforms Of Coastal Deposition We will look at three main landforms other than standard beaches: 1)Spits 2)Bars 3)Tombolos

66 Spit Photograph Spit Longshore Drift

67 Spit bay longshore drift

68 Spit spit bay longshore drift

69 Spit help

70 Bar Photograph BarLagoon Longshore Drift

71 Bars Bay longshore drift

72 Bars lagoon longshore drift bar

73 Bar help

74 Tombolo Photograph Island Tombolo Longshore Drift

75 Tombolo island bay longshore drift

76 Tombolo island bay tombolo spit

77 Tombolo help

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