Lesson video

Hello and welcome.

My name is Ms. Harrison.

I'm so looking forward to learning with you today.

Today's lesson is called "The Role of Climate, Marine, and Sub-Aerial Processes in Coastal Erosion." By the end of today's lesson, you'll be able to explain the role that climate, marine, and sub-aerial processes play in coastal erosion.

Before we can begin this learning, we need to define the keywords that we'll be using throughout this lesson.

The keywords we'll be using throughout today's lesson are erosion, constructive wave, destructive wave, weathering, and mass movement.

Erosion.

This is the wearing away of rocks along the coastline.

Constructive waves.

They are low energy waves that result in the buildup of sediment along the coastline.

Destructive waves.

They are high energy waves that result in the removal of sediment along the coastline.

Weathering.

They're the breaking down or dissolving of rocks through plants, animals, and weather.

Mass movement.

This is the downhill movement of sediment due to gravity.

Fantastic.

We've defined these keywords.

We can now begin our learning.

The first learning outcome in today's lesson is, "How does climate affect coastal erosion?" Coastal landscapes are shaped by erosion, transportation, and deposition.

Erosion rates are influenced by several climatic factors.

For example, seasonality, storm frequency, and prevailing winds.

Seasonality refers to the change in weather patterns throughout the year.

For example, in winter, we'll experience stronger winds, and therefore high wave energy, and this will lead to increased erosion.

Whereas in the summer, we experience much calmer conditions, which often result in less erosion and actually more sediment deposition.

True or false? In summer, stronger winds and higher waves increase coastal erosion in the UK, while winter's calmer conditions reduce erosion.

Pause the video here, and press play when you're ready to continue.

Let's check our answer.

It's false.

Are you able to explain why? Pause the video here and press play when you're ready to continue.

Excellent work.

Stronger winds and high wave energy are usually going to occur in winter, and this then leads to increased coastal erosion.

Whereas in the summer, we generally have calmer conditions, and they result in reduced erosion and more sediment deposition.

We also have storm frequency.

Storm frequency relates to the number of storms occurring in a given period.

Storms produce powerful waves, and as such, they increase the rate of erosion.

Coastlines that experience high storm frequency are likely to have higher rates of erosion, whereas coastlines with lower storm frequency are likely to have more deposition going on.

Climate change may also increase the number of storms and their intensity.

And they do this by increasing the ocean temperatures.

Let's test our knowledge.

How does high storm frequency affect coastal erosion? Is it A, it decreases coastal erosion, because more frequent storms bring more sediment to the coast? B, it increases coastal erosion because more storms mean more wave energy hitting the coast? And C, it has no significant impact on coastal erosion, as storm frequency does not affect wave energy? Pause the video here whilst you decide, and press play to continue.

Fantastic.

The answer to this question is B.

It increases coastal erosion because more storms means more wave energy hitting the coast.

Well done.

Prevailing wind is the most common wind direction in an area, and prevailing wind impacts erosion because strong prevailing wind will increase erosion, and winds influence the direction of longshore drift.

This will therefore affect how sediment is transported and deposited along the coastline, and this can impact the rates of erosion.

True or false? Prevailing wind always reduces erosion.

Pause the video here and press play to continue.

Let's check our answer.

The answer is false.

Are you able to explain why? Pause the video here and press play to continue.

Fantastic work.

Prevailing wind refers to the direction the wind most commonly comes from.

Therefore, if the prevailing wind comes from a direction that brings powerful waves to a coastline, then erosion would be higher than in places where prevailing wind was weaker, and the waves they created were weaker too.

Seasonality, storm frequency, and prevailing winds will always work together.

A coastline with frequent storms, a strong prevailing wind, and stormy winters, is likely to experience rapid erosion.

Geology will also play a role here, too.

If it has weak geology, the erosion rate will be higher than if it has a harder geology.

The Holderness Coast is located on the east coast of England.

It is one of Europe's fastest-eroding coastlines.

It retreats up to two metres per year.

This results of high storm frequency from the North Sea, together with the coast's geology.

We can use old and new maps of the Holderness Coast to show the scale of coastal retreat.

Can you see how much closer Mappleton is to the sea on the modern map than it is in the historic map? Well done.

Which is one reason for the rapid erosion of the Holderness Coast? Is it A, frequent North Sea storms with strong winds? B, calm summer conditions and low wave energy? Or C, high rates of sediment deposition from nearby rivers? Pause the video here and press play when you're ready to continue.

Let's check our answers.

The answer is A.

Frequent North Sea storms with strong winds is the reason for rapid erosion of the Holderness Coast.

I would now like you to fill in the blanks using the words below for this gap fill about "How does climate affect coastal erosion?" Pause the video here, and press play when you're ready to continue.

Excellent work.

You should have been able to fill in the blanks using the words on the previous slide.

Your text should now read as like this.

"Changes in seasonality throughout the year affect coastal erosion.

For example, winter storms may cause more erosion than the calmer weather in summer.

The frequency of storms in a region can significantly alter coastal erosion patterns.

Coastlines with less frequent storms may experience lower rates of coastal erosion.

Prevailing winds can also impact coastal erosion by shaping waves and sediment movement along the coast." Well done.

We're now going to begin our second learning outcome, and this is to do with, "How do marine processes affect coastal erosion?" Coastal landscapes are shaped by various different marine processes.

When we use the word "marine", it simply relates to the sea.

There are a number of different processes that involve the sea.

For example, constructive waves and destructive waves, and specific erosional processes, such as hydraulic action, attrition, abrasion, and solution.

The strength of a wave will depend on certain factors.

The distance the wave has travelled, which is also known as the fetch, and the speed of the wind.

The longer the fetch, the more energy from the wind transfers to the water.

So a longer fetch will result in a larger and stronger wave, whereas a shorter fetch will result in a smaller and weaker wave.

When we learn about waves, it's really important to understand words we use to describe the features of wave movement.

We use "swash" to describe the movement of water up the beach after a wave breaks, carrying sediment and debris onto the shore.

And "backwash", the flow of water returning down the beach after swash, pulling sediment back into the sea.

As you can see from this, on the screen, the swash is moving up the beach and will be bringing sediment with it, whilst the backwash will be returning sediment back to the sea.

I would now like you to define swash.

Is it A, the movement of water up the beach after a wave breaks, carrying sediments and debris onto the shore? B, the flow of water returning down the beach after swash, pulling sediments back into the sea? Or C, the flow of water up and down the beach, pulling sediment back into the sea? Pause the video here whilst you decide, and press play when you're ready to continue.

Excellent.

The definition of swash is A.

The movement of water up the beach after a wave breaks, carrying sediment and debris onto the shore.

Well done.

When we look at waves, there are two different types of waves.

The first wave we're going to look at are constructive waves.

Constructive waves are low energy waves that build up the coast.

They will always have a strong swash, and a weak backwash.

This is because they'll be using all their energy to carry the sediment up the beach, and they'll have no more energy to bring it back down to the sea.

The waves are also extremely low, and they'll break further apart from each other.

We have destructive waves, and these are high energy waves that cause significant erosion along the coastline.

They will have a strong backwash and a weak swash.

This is because the backwash will be taking the material away, whereas when the swash is coming, it's not bringing any material up the beach.

Waves are steep, and they'll break frequently, so they'll be very close together, increasing the pressure along the coastline.

True or false? Destructive waves build up beaches.

Pause the video here whilst you decide, and press play when you're ready to continue.

The answer is false.

Are you able to explain why it's false? Pause the video here and press play to continue.

Excellent.

We know destructive waves cause erosion because they have a strong backwash, and this removes material and it has a weak swash.

Constructive waves, they build up the beach, as they have a strong swash, which deposits material, and a weak backwash, which doesn't bring any material back into the sea.

Erosional processes on the coast occur when waves constantly hit rocks and cliffs and they gradually wear them away.

These processes begin to shape our landscapes.

They create land forms, cliffs, caves, and arches, and they also cause coastlines to retreat.

One of the types of erosional processes is hydraulic action.

This is the process where waves compress air into cracks of coastal rocks, and they cause the rock face to break apart over time.

We have attrition.

This is the process where rocks and sediment collide and break together into smoother, smaller pieces.

An easy way to remember this is "attack" has "A-T-T", and "attrition" has "A-T-T", so when attrition is happening, rocks are colliding.

They're attacking each other.

Abrasion.

Abrasion occurs when sediment carried by waves scrape against the cliff face, wearing away the rock surface.

Another easy way to remember this is, when something's abrasive, like on a sponge, you have an abrasive side that's very hard, that rubs against the plates or whatever material.

The exact same is happening here.

Abrasion is the rough rock scraping along the cliff face and wearing away the rock surface.

We also have solution.

This is when acidic water dissolves soluble materials, such as limestone, and slowly erodes away rock surfaces, making them a lot weaker.

Let's test our knowledge.

Which statement best describes the difference between abrasion and solution in coastal erosion? Is it A, abrasion is a scraping of rocks against the cliffs by waves, while solution involves rocks breaking apart due to the air pressure? Is it B, abrasion is the grinding of rocks against the cliff face while solution dissolves soluble materials in rocks by seawater? Or C, abrasion is the dissolving of minerals in rocks by seawater, while solution is the grinding down of cliffs by rocks and sediment? Pause the video here and press play when you're ready to continue.

Excellent.

The statement that best describes the difference between abrasion and solution in coastal erosion is B, abrasion is the grinding of rocks against a cliff face, while solution dissolves soluble materials in rocks by seawater.

Well done.

I would now like you to change the terms below so they match the correct definitions of these erosional processes.

Pause the video here and press play when you're ready to continue.

Excellent work.

We should have been able to correctly change the terms so they match the correct definitions.

Abrasion occurs when sediment carried by waves scrapes against the cliff faces and begins to wear away the rock surface.

Solution.

It's the process where acidic seawater dissolves soluble minerals, such as calcium carbonate, and slowly erodes rock faces.

Hydraulic action.

The process where waves compress air in the cracks of coastal rocks, causing the rock face to break up over time.

And attrition, the process where rocks and sediment collide and break into smaller, smoother pieces.

Well done.

We're now beginning our third learning outcome, and this is how do sub-aerial processes affect erosion? Sub-aerial processes occur on land, and they influence coastal landscapes through weathering and mass movement.

Mass movement simply refers to the movement of soil and rock down a slope due to gravity.

We have three main types of mass movement.

They're rockfalls, landslides, and slumping.

Which of the following best defines mass movement? Is it A, the rapid and explosive ejection of magma and gases from a volcano? B, the downward movement of soil, rock, and debris, under the influence of gravity? Or C, the lateral spreading of sediments due to wave action in coastal areas? Pause the video here and press play when you're ready to continue.

Fantastic.

It is B.

The downward movement of soil, rock, and debris, under the influence of gravity, is the best description of mass movement.

Rockfalls are rapid falls of rock from a cliff.

When pieces of rock become loose, often because of weathering, they break off and fall straight down.

This sudden movement creates a pile of rocks, called scree, at the base of a cliff.

Rockfall is usually very fast, and it happens on steep and vertical slopes.

Landslides are when large masses of rock or soils slide down a slope.

In a landslide, large sections of rock suddenly slide down a slope, staying mostly in one piece.

It's like if you had a big sheet of material that loses its grip and just slips down the hillside.

Landslides are usually triggered by heavy rain, earthquakes, or human activity, which can make the slope unstable.

They're also faster than slumping, because the material slides down in a more rigid way.

Slumping is the rotational movement of material along a curved surface.

Slumping happens on softer materials like clay.

When the base of a slope gets eroded, like the bottom of a cliff, the weight of the material above causes it to slip down in a rotational movement.

It's like the slope is folding over itself in chunks.

This often happens when the ground becomes saturated with water, making it heavier and more likely to slump.

What is the key difference between a landslide and slumping? Is it A, landslides involve rotational movement along a curved surface, while slumping occurs straight down a slope? B, slumping involves rotational movement along a curved surface, while landslides move straight down a slope? Or C, landslides occur when rocks fall off a cliff while slumping involves a rotational movement along a curved surface? Pause the video here, and press play when you're ready to continue.

Fantastic.

The answer for the key difference between a landslide and slumping is B.

Slumping involves rotational movement along a curved surface, while landslides move straight down a slope.

Weathering is the breaking down of rocks and minerals at or near Earth's surfaces.

There are three types of weathering.

We have physical weathering, we have chemical weathering, and biological weathering.

Physical weathering is the breakdown of rocks into smaller pieces without chemical change.

For example, freeze-thaw weathering.

Freeze-thaw weathering is when water enters cracks in the rock, it freezes, and this expands.

Eventually, they will thaw.

This freezing and thawing process will be repeated, and will cause pressure on the rock.

Eventually, it will cause the rocks to crack and break apart over time.

Chemical weathering is the breakdown of rocks due to chemical reactions.

One example is when weak acids in seawater gradually dissolve minerals, like the calcium carbonate in limestone.

Aisha has correctly identified that when carbon dioxide dissolves in seawater, it forms weak carbonic acid.

Biological weathering is the breakdown of rocks due to biological activity, through plants or animals.

For example, in the image on the screen, we can see plant roots grow into cracks and they break the rocks apart, because they put pressure on it.

I would now like you to number the descriptions to match the steps shown in the diagram of freeze-thaw weathering.

Pause the video here, and press play when you're ready to continue.

Excellent.

We should have number one, as water enters cracks in the rock.

Number two, the water freezes when the temperature drops.

Number three, freezing water expands and puts pressure on the rock.

And four, repeated freeze-thaw cycles widens the cracks, and eventually the rock breaks into smaller pieces.

Well done.

I would now like you to explain the difference between physical weathering and chemical weathering at the coast.

Make sure to remember these things.

You need to make two distinct points here.

One for physical, and one for chemical weathering, and you must include a description and an example of the processes that occur.

Pause the video here and press play when you're ready to continue.

Excellent.

Your answers might include something like this.

Physical weathering is the process where rocks are broken into smaller pieces without any chemical changes.

This often occurs through processes such as freeze-thaw weathering, where water enters cracks in the rock, freezes, and expands, and this causes the rock to break apart.

Chemical weathering, on the other hand, involves the breakdown of rocks through chemical reactions.

One example is when weak acids in seawater gradually dissolve minerals, like the calcium carbonate in limestone.

Excellent work.

You've done brilliantly in today's lesson, and you've worked really really hard in learning about the role of climate, marine, and sub-aerial processes in coastal erosion.

Before we end this lesson, let's summarise all the learning that we've done in today's lesson.

Climate plays a really important role in the rate of erosion at a coastline.

Seasonality, prevailing winds, and storm frequency affect the rates of erosion.

We have specific marine erosional processes, like hydraulic action, attrition, abrasion, and solution, and they erode the coastline.

We also know about the two different types of waves.

Constructive waves build beaches by depositing sand as they have a strong swash and a weak backwash, while destructive waves erode beaches, especially during storms, because they have a weak swash and a strong backwash.

We also learned about sub-aerial processes such as weathering, which break rocks through biological, physical, or chemical, and we learned about mass movement, which removes material from the cliffs through landslides, rockfall, and slumping.

Well done in today's lesson, and I look forward to landing with you again very soon.