Chapter 1: Coasts

Chong Boon Secondary School Pure Geography

Physical Geography

Lesson 1

Key thinking questions

• Should coastal environments matter?• How and why are coastal environments

different and dynamic?• Why are coastal areas valuable?• How can we manage coastal areas in a

sustainable manner?

What are coasts?

• The area where land meets the sea• Affected by various agents – waves,

tides and currents• Divided into various zones –

offshore, nearshore, foreshore and backshore

• There are various types of coastal environments (pg 5)

Parts of a coast (pg 5)

• Offshore – submerged region extending out to the sea

• Nearshore – always submerged below the low-tide level, area where breakers start forming

• Foreshore – submerged during high-tide but exposed during low-tide

• Backshore – where the berm is usually found

Factors that affect the coast

• Tides – daily alternate rise and fall in the sea level caused by gravitational pull of the moon and sun

• Sea level changes – change in sea levels due to ending of ice age or climate change

• Currents – large scale and continuous movements in the oceans and seas

Watch the videos on the FB page on how tides and currents work.

Factors that affect the coast

• Geology – refers to the composition and also the arrangement of rocks found at the coastal area

• Ecosystems – affects the rate of coastal changes by reducing the impact of waves

Evaluation• You have 5 minutes to relook at the

information.• After 5 minutes, you will attempt the mini

test.• You have 10 minutes to complete the test.

Mini Test In Progress

Group activity 1• What is a coast? Select a suitable cross section

diagram that will show the parts of the coast.• List down what your team feels are the 2 main

factors that affect the coastal environment.– 15 minutes, discuss and put down what your team

feels is correct.– Point form.– Put up your answers once you are ready.– Assign your presenter(s).

Presentation Time• Presenters please stand by your

answers.• Present your answer.• 2 minutes maximum!

Individual activity(use the blank side of the minitest)

• Copy the questions and answer it in the blank space.

Q1 Using only a fully labelled diagram, show what the parts of a coast. (4m)

Q2 List and explain two factors that affect the coastal environment (4m)

Optional

Homework reminder

• Read up pg 9 to 16.

• Focus on the Coastal Erosional Processes &

Waves.

Lesson 2Wk 2

Let’s take a look at your 1st mini test

Please take out your worksheet

Self Evaluation

• Let’s look at the key thinking questions for this part of the chapter.

Key thinking questions

• What affects a wave’s speed and energy?• What are the parts of a wave?• What is a swash / backwash?• Why do waves break near the coast?• What is the difference between

Destructive and Constructive waves?

Factors that affect waves • Wind speed• Duration of wind• Fetch – refers to the distance of

open sea that is exposed to effects of wind

How does each factor affect wave energy?

Waves in general…• As waves approach the coasts, the

depth of the water becomes shallower

• When the depth is about half of the wavelength, the wave starts to change

• The base of the wave starts to slow down due to friction

• Wave height increases and wavelength decreases

Waves in general…

• When the base of the wave stops, the wave crest becomes steeper and topples over

• This causes the wave to “break” over the coast and releasing the wave energy

• Surfers are always in search of these breaking waves to ride over them

• *breakers, breaking waves

Waves in general…• Swash: water moving up the shore,

brings sediments in• Backwash: water moving down the

shore, carries sediments away• Constructive waves: waves with

swash more powerful than the backwash

• Destructive waves: waves with backwash more powerful than the swash

Wave refraction• Refers to a process where waves

change direction as they approach the coast

• *** Refraction occurs because wave energy will always approach the coast perpendicularly

• Refraction therefore causes wave energy to concentrate on headlands and spread out at bay areas

Group activity 1• Using only a diagram, show the various parts

of the wave. (Crest, Trough, Wave height, Wave length)

• Explain how any 2 given factors affect the size and energy of waves.

• With the aid of a suitable diagram, describe what are constructive waves.– 10/20 minutes, discuss and put down what your

team feels is correct.– Point form.– Put up your answers once you are ready.– Assign your presenter(s).

Gallery Walk Time• Please put up your presentations on the

given space.• Let’s do a gallery walk.• You are to award stars to the presentations

that you feel are the best. • Each person has 2 stars only.• You should not give both to the same group.

Homework• Take a detailed look at the Investigation Task

(pg 10 & 11)• Refer to Pg 253-254 on how to construct a

scatter graph.• Refer to Pg 265 on how to annotate maps• Refer to Pg 264 on how to take and annotate

photographs.

Homework reminder

• Memorise the 4 coastal processes

on pg 15. • We will be looking at these on

Lesson 3.

Lesson 3

Individual activity

• Look at the exercise given, complete it to your best ability.

• You have 8 minutes.

What is C.A.S.H ?

COAStal erosion (c*A*S*H)

• Corrasion (Abrasion): when sediments such as sand and rocks scrape against the coast and breaks down the coast

• Attrition: when sediments rub or hit against one another and become smaller and more rounded

COAStal erosion (c*A*S*H)• Solution (Corrosion): when seawater

chemically reacts with the minerals in coastal rocks and dissolves them, e.g. limestone rocks are easily eroded by carbonic acid

• Hydraulic action: when the coast is struck by action of water, air within the joints are compressed and exert pressure, which weakens the rock structure

Group Activity

• In your groups, discuss and come up with a simple way to explain any 3 erosional processes. – It can be in the form of a dance/rap/song/

diagram/ skit / etc.– Your presentation must not be more than 3

minutes long.– You have 20 minutes to prepare.

Lesson 4

Individual activity corrections

• Look at the exercises I’ve returned.

• Let’s do corrections• File it in!

Prep for next lesson• Read Pg 16 carefully.• Watch the prescribed video on

Long shore drift• Practice drawing the diagram

Lesson 5

Key thinking questions

• What affects the transport of sediments on a coast?

• How does a piece of sediment move along the coast?

• What are longshore currents?• What is longshore drift?

Sediment transport• Refers to the movement of sediments

along the beach• Beach drift: zigzag movement of

sediments along the beach• Sediments move up the beach at an

angle as swash• Sediments move down the beach

perpendicularly as backwash

Sediment transport• Longshore currents: ocean

currents flowing parallel to the coastline

• Moves sediments along the shore

• Combine effect of transportation by longshore currents and beach drift is longshore drift.

diagram

Sediment deposition• Refers to the process where sediments

are let go and no longer carried by the waves due to loss of wave energy

• Usually larger sediments get deposited first (WHY?)

• Sheltered coasts with calmer waters have fine sediments

• Small bays tend to have coarser sediments

Self Evaluation

• Complete the timed exercise now.• You have 10 minutes.

Group activity 1

• Using only a diagram, show how a sand particle is moved along the beach.

• List and explain the four ways in which coastal erosion can occur.

• With the suitable diagrams, compare constructive waves and destructive waves– 30 minutes, discuss and put down what your team

feels is correct.– Point form.

Gallery Walk Time• Please put up your presentations on the

given space.• Let’s do a gallery walk.• You are to award stars to the presentations

that you feel are the best. • Each person has 2 stars only.• You should not give both to the same group.

Homework• Take a detailed look at the

Investigation Task (pg 17)

• Read Pg 17 to 29.

Lesson 6

Key thinking questions

• What are the landforms that are caused by waves?

• What coastal landforms are linked and related?

• Besides the force of water, what other materials are used to form the coast?

Sediment deposition• Refers to the process where sediments

are let go and no longer carried by the waves due to loss of wave energy

• Usually larger sediments get deposited first (WHY?)

• Sheltered coasts with calmer waters have fine sediments

• Small bays tend to have coarser sediments

Coastal features• Various landforms and

features can be found at coasts

• The types of features found tend to be due to factors such as type of waves, type of rocks (geology), the location, and human activities

Cliff and shore platforms

• Cliff: A steep or near-vertical rock face found along coasts

• Shore platform (or wave-cut platform): gently sloping platform usually found at the base of a cliff and submerged during high tides

Cliff and shore platforms

• Due to hydraulic action and abrasion, a joint or crack in the rocks may be enlarged to form a notch, usually found between the high and low tide mark

• The notch may be further eroded and enlarged to form a cave

• Further erosion and gravity eventually causes the roof of the cave to collapse

Cliff and shore platforms• This results in the formation of a steep

rock face, or cliff• With further erosion, undercutting

occurs at the base of the new cliff face• As the overhang collapses, the cliff

retreats inland• The gentle slope at the base of the cliff

where previous cliffs used to be is the shore platform

Headlands and bays• Occurs due to the uneven rates

of erosion of different rock types• Usually found in locations where

there are bands of alternating resistant and less resistant rocks

• What is an example of less resistant rock?

Headlands and bays• As the less resistant rocks are

more easily eroded, they give rise to bays

• The resistant rocks will stand out as headlands

• The formation of headlands and bays gives an indented coastline

Homework• Revise the entire set of

content we’ve covered so far.

• Next lesson we will do a mini test