Higher Coasts Lithosphere. Higher Coastal Landforms & Processes. In this part of the course we will be looking at both: coastal erosion and deposition. Coastal Erosion. We will be looking at the following: Waves our agent of erosion Different types of erosion Landforms of erosion.
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In this part of the course we will be looking at both:
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.
Fetch = Distance + Wind
Now for Task 2 all about waves actually breaking down rock, or erosion.
There are 3 ways thatwaves 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.
Crack In Rock
Air Compressed By Water
Over time rock weakens and breaks off cliff
Air explodes out of crack
Key words to describe hydraulic pressure.
breaking waves ~ cliff ~ water ~ cracks
compresses air ~ air explodes ~
rock ~ time ~ breaks ~ force of water pounding ~ erodes ~ time
Waves carry rocks, shingle, sand
Rocks hit each other
Rocks erode over time
Key words to describe corrasion.
broken rock ~ picked ~ waves
thrown ~ cliff faces ~ hard rock -erode ~ time
Waves carry rocks
Small rocks rub against cliff
Key words to describe attrition.
small rocks ~ H.P. ~ Corrasion
waves ~ rub ~ cliff ~ 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.
We shall look at three principal types of landforms:
i. Cliffs/Wave Cut Platforms
iii.Headland Erosion (On Sides)
Wave Cut Platforms
wave cut platform
sea cliff erosion
Cracks In rock are weak points
These are eroded by waves at high tides by the 4 processes we’ve looked
collapse of overhang
cracks get larger & form a cave
undercutting of cliff by cave
Repeated collapse over time
flat terrace remnant of base of cliff
Now do Task 3 Question 1 by filling in the key
W.C.P. exposed at low tide, but created at high tide
concordant parallel to sea
discordant at 90º to sea
crack in rock eroded by waves
hard rock resists waves so narrow crack
soft rock erodes easily so wide bay
softer rocks erode more easily than harder ones ~ differential erosion
indents or bays form on the coast
where the soft rock has receded
These are a series of landforms developing one after the other on the side of a headland.
Label the sketch below in your work book using the word box for task 7.
wave cut platform
erosion on side of headland
waves erode cracks into caves
Explain sedimentary rocks easily exploited many cracks
name your 3 types of erosion in exam
blowhole in top of headland
waves crash into back of cave and erode upwards into headland
blowholes are relatively rare
vertical cracks in rock help them to form
Roof collapses due to erosion from waves splashing upwards from back of cave
eventual break through to other side forms an arch
continued erosion of back of cave
process can be sped up if cracks on other side being eroded
little support so eventual collapse ofroof
further erosion sees widening of arch
process can be aided by blowhole weakening roof
Now try and piece together the explanations for all of these landforms Task 7 question 2
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.
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!).
6) At the same time caves and blowholes develop, wave
erosion can also lead to the development of an arch. This is when thecave 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!
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
water swashing up a beach
Now for Task 9 Question 1
Complete the passage
using the word box
rotation of wave
Now for Task 9 Question 2
wave ~ friction ~ seabed ~ elliptical ~
just before breaking ~ steep wave ~
rotates back ~ weak swash ~ strong
backwash ~ sediment lost ~
breaking swash breaks at angle on beach
Swash loses energy & backwash returns straight down beach due to gravity
Zigzag movement of sediment with swash & backwash means sediment moved along beach
direction of longshore drift
Explaining longshore drift Task 10
swash angle ~ energy loss ~ backwash ~
gravity ~ straight down ~ carries
sediment ~ up ~ down ~ along beach
We will look at three main landforms other than standard beaches: