Aim We must know and understand the following What do they look like What factors influence their formation What is coastal erosion Specification content Starter High and low energy coastlines ID: 760307
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Slide1
Rocky vs Sandy Coastlines
Aim: We must know and understand the following:
What do they look like? What factors influence their formation?
What is coastal erosion?
Slide2Specification content
Slide3Starter – High and low energy coastlines
https://
www.youtube.com/watch?v=6rG6IjJotWw
High energy = Rocky Coastlines
Low energy = Sandy Coastlines
https://
www.youtube.com/watch?v=HHcFiI8rx_g
Slide4Slide5T
there is HIGH ENERGY. EROSION exceeds deposition.
Slide6Slide7Sandy Coasts
Along a coastline you find features created by deposition. These include beaches, spits and
tombolos.These areas of deposition are LOWER ENERGY than that of rocky coastlines.Here the rate of DEPOSITION exceeds EROSION.
Slide8Geology – What is it and what influence does it have?
Definition of Geology
Geology is the study of the Earth, the materials of which it is made, the structure of those materials, and the processes acting upon them. It includes the study of organisms that have inhabited our planet. An important part of geology is the study of how Earth’s materials, structures, processes and organisms have changed over time.
The geology of the cliff is a really important factor that influences the rates of erosion. The resistance of rock essentially determines
differential rates of erosion
. This in turn shapes our coastlines.
Slide9Geology – What is it and what influence does it have?
The
red line is an imaginary line that can be drawn to separate different types of geology.Its called the Tees –Exe Line which roughly divides the country into lowland and upland regions.To the south and east of this line, the landscape, whilst not always flat is certainly lower and is characterised by flat-lying or gently tilted or folded sedimentary rocks. North and west of this line are the older, generally harder rocks including igneous and metamorphic rocks and the Palaeozoic and Precambrian sandstones and limestones which usually stand out as upland areas.
Slide10Coastal processes
http://
thebritishgeographer.weebly.com/coastal-processes.html
https://
www.youtube.com/watch?v=zUh3WeilFN4
How does coastal erosion occur?
occurs due to wave and current activity,
high winds making larger waves, action of high tides. Resistance to erosion and hardness of rocks
.
Sea
levels rise and storms increase in frequency and severity, coastal erosion can
increase. Coastal
erosion is a mostly natural process; however, man-made structures such as piers and
harbours
can contribute to erosion due to restructuring of the natural environment.
Take a look at some images of dramatic coastlines which have been shaped by coastal erosion!
Slide11Hangman Cliffs, Devon 318m above sea level
Slide12Hangman Cliffs, Devon 318m above sea level
Slide13Boulby
Cliffs, N Yorkshire 203m above sea level
Slide14https://www.youtube.com/watch?v=ht6_tgYt0lc
Boulby
Cliffs
You don’t have to watch every second of this to get the gist!
But please take a mental note of:
The height and steepness of the cliffs
The rock type – hard, soft geology
The backshore, foreshore, nearshore and offshore areas
The shape of the coastline
Slide15Conachair
Cliffs,
Hirta
, Outer Hebrides 427m above sea level
Slide16Slide17Weathering
Weathering
Weathering is the breakdown of rocks at the Earth’s surface, by the action of rainwater, extremes of temperature, and biological activity. It does not involve the removal of rock material.
There are three types of weathering,
physical
,
chemical
and
biological
.
How is erosion different to weathering?
Erosion is the process by which soil and rock particles are worn away and moved elsewhere by wind, water or ice. Weathering involves no moving agent of transport.
Slide18Weathering and Erosion are not the same!
Highlight the definition of weathering at the top of the next page and make sure you read the Geofactsheet for homework! :-)
Hydraulic action
. Air becomes trapped in
joints and cracks
in the cliff face. When a wave breaks, the trapped air is compressed which weakens the cliff and causes erosion.
Abrasion.
Bits of rock and sand in waves are flung against the cliff face. Over time they grind down cliff surfaces like sandpaper.
Attrition.
Waves smash rocks and pebbles on the shore into each other, and they break and become smaller and smoother.
Solution
. Weak acids contained in sea water will dissolve some types of rock such as chalk or limestone.
Slide19Definitions
ErosionTransportation Erosion
Rocky coastlines and sandy coastlines are different due to these processes below:
Slide20Definitions
Erosion = the wearing away of the land by forces such as water(rivers and marine), wind, and ice. Transportation =The four different river transport processes. Solution - minerals are dissolved in the water and carried along in solution. Suspension - fine light material is carried along in the water. Saltation - small pebbles and stones are bounced along the river bed.Deposition= is when eroded material is dropped by constructive waves(coastal geography). It happens because wave have less energy.
Rocky coastlines and sandy coastlines are different due to these processes below:
Slide21Coastal Erosion
occurs due to many PHYSICAL PROCESSES that are constantly in action.Erosion creates many different LANDFORMS which we will learn about later in the topic.*****We will come back to this flow diagram later in the topic and discuss in more detail
Add these key words to the
flow
diagram on the next page.
Use
different colours to make it
stand
out
HIGH ENERGY
LOW ENERGY
ROCKY COASTS
SANDY COASTS
POWERFUL WAVES
GENTLE WAVES
LESS EROSION
MORE EROSION
MORE DEPOSITION
LESS DEPOSITION
HEADLANDS
BEACHES
Slide22Coastal Erosion
occurs due to many PHYSICAL PROCESSES that are constantly in action.Erosion creates many different LANDFORMS which we will learn about later in the topic.*****We will come back to this flow diagram later in the topic and discuss in more detail
GENTLE WAVESLESS EROSION
SANDY
COASTSLOW ENERGY
BEACHES
MORE DEPOSITION
HEADLANDS
ROCKY COASTS
LESS DEPOSITION
POWERFUL
WAVESMORE EROSION
Slide23You must know your ROCK TYPES
Before
we can discuss the influence of GEOLOGY any further we must know and understand the three main rock types. Complete the card sort on ROCK TYPES and create a spider
diagram.
Slide24Rock strata structures
The geology of a rock affects how its resists breakdown(weathering) and how fast it wears away(erosion)
Another important factor is
Rock
S
tructure or Geological Structure
This can determine how fast rocks at the coastline are shaped. The shape of the coast is called
coastal morphology
https://
www.youtube.com/watch?v=SoOb4fg7cqk
Highlight the images within your booklet p29 using the next PPT slide
Then use pages 114 and 115 to define each key term
Slide25Bedding planes, Dip of rocks, faults and joints/fissures
Faults
Bedding Planes
Dip of rocks
Slide26Fissures
Folding
Rock layers laid
down horizontally
Rock layer/unit C
Is the oldest.
Rock layers are buckled Upwards into an ANTICLINEdue to a tectonic event.
Over millions of years the land surface
undergoes weathering and erosion to produce
an eroded uneven surface, exposing the repeated
l
ayers.
Slide27Slide28Add notes from textbook p114 and 115 into booklet p30
Understanding ‘Dip of rocks, faults, joints and fissures’
Slide29Resistant Headland-
Dolerite(Hard Igneous
Rock)
Horizontal layered sedimentary rock -Limestone
Anticline exposed on
t
he foreshore
composed
o
f limestone
.
Slide30Same location as previous photo but from a different angle
Resistant Headland-
Dolerite(Hard Igneous
Rock)
Anticline and syncline exposed on the foreshore composedof limestone.
Slide31Lulworth
Crumple
Stair Hole
Slide32Geology and Erosion
Explain
how rocks and their resistance to erosion influence the height and shape of our coastlines (read left hand side of page 112 to help you)
Slide33Marine and Sub aerial cliff profiles
Make
sure you include what is/define MARINE EROSION and SUB-AERIAL EROSION (p111 & top of p112)
Draw each cross profile from the textbook P111
Slide34Coastal Plains
These are low lying areas, low relief and close to the coastline.Low energy, lacking large powerful waves(except in rare occasions such as storms or hurricanes)Typical areas are wetlands and salt marshes just above sea level.
Kent, SE England
They form in two ways:
Fall in sea level which exposes the sea bed/ shallow continental shelf, e.g Atlantic coastal plain USADeposition of sediment brought down by rivers which gradually build out to sea, causing a delta. This process is called coastal accretion(creation of new land which can be stabilised by vegetation)Many coastal plains are in equilibrium(in balance) as rivers bring sediment, plus sediment brought in from offshore zones and longshore driftAt the same time is balanced by erosion from marine action
****Dynamic Equilibrium =
balanced system in INPUTS & OUTPUTS. If the
n
atural system is upset by outside influences the internal system is upset.
Feedback adjusts to the change and equilibrium is restored.
Slide35The formation of HEADLANDS and BAYS will be part of the focus for the next lesson
HOMEWORK – Complete the questions on p34 of the booklet using these images above
Slide36Do these images suggest high energy or low energy? The energy of the waves at the coastline is another important factor influencing the coastline shape. What is the energy level at a coastline which has headlands and bays? Explain your answer.
They suggest high energy at rocky coastlines.
Why?
The evidence is from the landforms caused by erosion such as headlands, natural arches, stacks, stumps. The rocks here resist erosion and therefore these features are the result. There is minimal deposition at these locations and very often the beaches are thin or narrow. Waves at high energy coastlines are usually destructive and take material away rather than build it up.
At bay locations it is the complete opposite. These are areas of deposition, lower energy and constructive waves which build up beach sediments providing large, wide sandy beaches.
**We will look into energy levels and wave types later on in the topic.