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Higher Coasts Lithosphere

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Presentation on theme: "Higher Coasts Lithosphere"— 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:
Waves our agent of erosion Different types of erosion 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 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 Air Compressed By Water
Hydraulic Pressure Crack In Rock Breaking Wave Air 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 ~ cracks compresses air ~ air explodes ~ rock ~ time ~ breaks ~ force of water pounding ~ erodes ~ time

14 Waves carry rocks, shingle, sand
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 Small rocks rub against cliff
Attrition Waves carry rocks Small rocks rub against cliff

17 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 Platforms wave cut platform
(Task 3) wave cut platform sea cliff erosion

21 Cracks In rock are weak points
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 collapse of overhang cracks get larger & form a cave
undercutting of cliff by cave

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

24 Now do Task 3 Question 1 by filling in the key
Sea Cliff Erosion Now 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 Platform W.C.P. exposed at low tide, but created at high tide for later

26 Task 3 Question 2 Waves ~ erosion ~ 4 types ~ name ~ general effect ~ high tide Cracks ~ weak ~ widen ~ wave cut notch ~ cave ~ time ~ overhang ~ collapse of cliff (why) ~ repeats ~ retreats Base 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 & Bays concordant parallel to sea two types discordant at 90º to sea

29 crack in rock eroded by waves
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 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 3 Geology ~ 2 key factors ~ (1) different rock types ~ hard ~ soft ~ side by side ~ (2) Layers 90º ~ sea 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
needle wave cut platform cave arch

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

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

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
eventual break through to other side forms an arch continued 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 roof further 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:- 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: Swash & Backwash Beach Profiles Beach Angle & Wave Type Longshore Drift Landfroms Of Deposition

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

53 Swash & Backwash swash backwash

54 water swashing up a beach
Swash & Backwash water swashing up a beach

55 Why Beaches Develop Swash & Backwash Task 8

56 Gentle Beach Constructive Waves
strong swash circular elliptical 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
elliptical wave circular wave weak swash rotation of wave strong backwash

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 breaking swash breaks at angle on beach
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 direction of longshore drift
swash backwash direction of longshore drift moving sediment

64 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: Spits Bars Tombolos

66 Spit Photograph Longshore Drift Spit

67 Spit bay longshore drift

68 Spit bay spit longshore drift

69 Spit help

70 Bar Photograph Longshore Drift Lagoon Bar

71 Bars Bay longshore drift

72 Bars lagoon bar longshore drift

73 Bar help

74 Tombolo Photograph Island Longshore Drift Tombolo

75 Tombolo bay island longshore drift

76 Tombolo bay spit island tombolo

77 Tombolo help



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