Hello, my name's Mr. March and I'm here today to teach you all about processes at conservative plate margins.

So grab everything that you need for today's lesson and let's get going.

So by the end of today's lesson, you will be able to explain the processes at conservative plate margins and relate these to the causes of earthquakes.

There are two key terms for today's lesson, and those are magnitude and magma.

Magnitude refers to a measure of the energy released by an earthquake.

A higher magnitude means a stronger earthquake.

And magma refers to molten rock found beneath Earth's surface.

It is formed when rocks in the earth's mantle or crust melt due to high temperatures and pressure.

There are two learning cycles for today's lesson, and we're gonna start with the first learning cycle, which is what are conservative plate margins.

Now, on the map in front of you of the USA, you can see Los Angeles and San Francisco marked, and it is over 550 kilometres from San Francisco to Los Angeles.

Now, my question to you is why might they be at the same location in around 20 million years? You may like to pause the video here whilst you consider your own answer or discuss this question with someone near you.

Now, the reason why Los Angeles and San Francisco will still be the same distance apart even 20 million years from now is because they lie on what we know as a conservative margin, a conservative plate margin.

And as the diagram in front of you shows, this is where plates slide alongside each other.

And they may be travelling in different directions, as the diagram shows, or they may be travelling in the same direction, but at different speeds.

In front of you then we've got a learning check and it says which of these shows a conservative margin? Now, I would like you to pause the video here whilst you look at the three diagrams in front of you and then consider and select your answer.

And the correct answer was C.

Really, really well done if you were able to identify that as the correct answer.

So unlike constructive margins or destructive margins, conservative margins do not produce major landforms. They do not produce any volcanic activity because crust is not being destroyed or constructed.

There are no mountains here because the plates are not smashing or colliding into one another, and there are no volcanoes created as well.

Finally, there are no ocean trenches because no subduction is actually taking place here.

There is no tectonic plate which is sinking into the mantle.

So conservative margins though do feature faults, which are cracks in the crust, and they do have some of the most powerful earthquakes ever recorded.

Time once again for a learning check.

And this one says which of these are features of conservative plate margins? Now, you have four options in front of you.

I would like you to pause the video whilst you consider and then select all answers that apply.

Best of luck.

And the correct answer was D, earthquakes.

Yes, whilst A, B and C, volcanoes, ocean trenches, and fold mountains are associated with constructive or destructive plate margins, the only feature associated with conservative plate margins are earthquakes.

So really, really well done if you were able to identify that as the correct answer.

The San Andreas Fault is a conservative plate margin found on the western side of the USA.

Part of it is centred around Los Angeles and San Francisco that we looked at before.

So the North American Plate and the Pacific Plate are both moving in a northwesterly direction as this enhanced image of this map shows.

They're both moving generally in the same direction, but the North American Plate is moving more slowly than the Pacific Plate.

What does this mean in terms of the location of Los Angeles and San Francisco? Well, in terms of the fact that they're moving generally in the same direction, but at different speeds, it means that these two cities, over a huge amount of time, maybe 20, 30 million years, we don't know, but eventually, these two areas should come closer and closer together.

We have now just one practise question and it says this, using the information on the satellite image and your own knowledge, explain why Los Angeles may be at the same location as San Francisco in 20 million years.

So what I'd like you to do then is pause the video whilst you study the map in front of you and consider your prior knowledge from today's lesson and attempt this answer.

So pause the video here and best of luck.

Time now for some feedback.

So if we're looking at that map in front of you, this is what your answer may have said.

It says that San Francisco is on the North American Plate and Los Angeles is on the Pacific Plate.

The Pacific Plate and the North American Plate are both moving in the same direction, northwest, along at a conservative fault.

But the Pacific Plate is moving faster.

So over the next 20 million years, Los Angeles will catch up with San Francisco until it is alongside it, as long as the two plates keep their current rate and direction of movement.

So really, really well done if you are able to include anything like that in your own answer.

We're on now to our second and final learning cycle, and this is all about the hazards which occur at conservative plate margins.

Now, the map in front of you is showing the impacts of a hazard at a conservative plate margin, and we can see that the colours are denoting different levels of strength of that hazard.

Now, what I'd like you to do is to consider what hazard this is actually showing us.

So you may like to pause the video here whilst you study that map and consider your own answer to that question or perhaps discuss it with someone next to you.

Sofia is absolutely right in that she can see that an epicentre can be seen, as well as shaking, as we can see with the legend where it says perceived shaking.

Sofia is absolutely right when she identifies it as being an earthquake.

So really well done if you too were able to identify it as an earthquake.

So time now for a learning check, and it says, which of the circles indicates a conservative plate margin? Now, what I'd like you to do is pause the video whilst you study that map in front of you, and you can see you have A, B, C, D, and E to consider as to which are showing a conservative plate margin.

So pause the video here whilst you consider and then select your answer.

And the correct answer was C.

And Lucas is absolutely correct when he says, "Because it shows plates sliding alongside each other." Yes, if we really study that map, C is the only area on that map where we can see two plates sliding past one another.

So really well done if you too were able to select C as the correct answer.

Now, earthquakes are the primary hazard or the foremost hazard that occur along a conservative plate margin.

Remember, there are no volcanic eruptions occurring along a conservative plate margin.

Other hazards though, known as secondary hazards, are triggered by earthquakes.

For example, landslides.

Earthquakes can trigger landslides when the movement of the Earth makes slopes unstable, especially on steep slopes, deforested slopes, et cetera.

For tsunamis, the earthquake occurring under the ocean can cause a sudden upward movement of the crust, which can displace huge volumes of water and generate waves that reach the coast as a tsunami.

And these can be up to 30 metres tall.

For fires then, earthquakes can fracture gas pipes and bring down electricity lines, both of which can then start fires.

For example, in 1906, a conservative plate margin earthquake in San Francisco caused fires that burnt down most of the city.

Fires like these would be categorised as a secondary hazard with the earthquake as a primary hazard.

Remember, a secondary hazard is a knock-on hazard caused by the primary hazard, in this case, an earthquake.

Another example of a really powerful earthquake that struck along a conservative plate margin was unfortunately in 2010 where an earthquake struck the city of Haiti, as well as the Dominican Republic, and it had a magnitude of 7.

0.

The epicentre was 25 kilometres west of the capital city of Haiti called Port-au-Prince, and an estimated 230,000 people died from this event and 300,000 were injured and 1.

5 million people were unfortunately made homeless.

So a quick learning check.

It says, which of these statements would you agree with? We have statements from Aisha, Andeep and Jacob.

And what I'd like you to do then right now is pause the video whilst you read through those three statements and consider and then select your answer.

And the correct answer was Aisha.

Aisha said that earthquakes at conservative margins can be high magnitude.

Now, we know this to be the correct answer because we know that the Haiti earthquake was on a conservative plate margin and had a high magnitude of 7.

0.

Andeep's answer is possibly confusing.

Conservative and constructive plate margins.

But we know it is wrong because conservative margins are at the edges of tectonic plates, not in the middle of them.

Jacob's answer is wrong because earthquakes are the primary hazard at conservative margins.

In fact, volcanoes do not occur at conservative margins at all.

So really, really well done if you too were able to select Aisha as the correct answer.

But what actually causes earthquakes at conservative margins? Well, as you know, it starts with those plates moving alongside each other.

Again, it can be going in different directions or it can be in the same direction, but at different speeds.

This is not a smooth process.

The plates get stuck due to friction.

This pressure builds up.

It creates an intense pressure, which can be created over sometimes hundreds of years.

When these stuck plates finally slip, the pressure is then suddenly released and violently released.

This violent release of seismic energy produces an earthquake.

The intense pressure then at conservative plate margins can produce very, very high-magnitude earthquakes.

And this is why it is one of the biggest or foremost primary hazards that we find at conservative plate margins.

Now, why is it that conservative plate margins do not produce volcanic eruptions? Well, let's have a look at the other plate margins to understand why they do produce volcanic eruptions.

Let's start with the destructive plate boundaries.

Now, at a destructive plate boundary, we can see from the diagram in front of you that a plate is sinking into the mantle and is being destroyed.

This process creates magma that leads to volcanic eruptions, very violent volcanic eruptions.

At constructive plate margins, we can see the two plates pulling apart and new crust is created or constructed as magma rises up between those two plates, as they pull apart, a process that leads to volcanic eruptions, albeit smaller volcanic eruptions than found at destructive plate margins.

At a conservative plate margin though, plates are conserved, they stay the same, not being destroyed, not being created, no magma is produced and therefore, no volcanic eruptions.

So a quick learning check, and it's true or false.

Volcanoes are hazards found at constructive and destructive plate margins, but not conservative plate margins.

So pause the video here whilst you consider your answer and then select your answer.

And the correct answer was true.

Now, once again, I'd like you to pause the video whilst you consider your own responses to why this statement is true.

And the reason it's true is because plates are not being created or destroyed at conservative plate margins.

No magma is produced, and this means volcanic eruptions are not a feature of these margins, unlike at constructive and destructive margins.

So really, really well done if you were able to identify those two correct answers.

We're on now to our one and only practise question for learning cycle two.

And it says, using the map and your own knowledge, explain why the Haiti earthquake of 2010 occurred.

So pause the video here whilst you study that map and recall your prior knowledge and then attempt this practise question.

Best of luck.

So time now for some feedback, and your answer may have included something like this.

It says that Haiti is located on a conservative plate margin.

The Gonave plate is moving westwards and the Caribbean plate is moving eastwards.

Earthquakes occur on conservative plate margins when the plates that are moving alongside each other become stuck.

Pressure builds up between the plates, sometimes for hundreds of years.

When the stuck plates slip, the pressure is suddenly released.

The violent release of seismic energy produces an earthquake.

And in the case of Haiti, the magnitude was very high at 7.

0.

So really, really well done if you too were able to get an answer, something similar to that in front of you.

In terms of our summary then, we need to know that conservative plate margins, the plates are moving alongside each other.

This may be alongside each other going the same direction or perhaps in opposite directions.

Earthquakes are the primary hazard at conservative plate margins, and these can be high magnitude, such as the 7.

0 magnitude earthquake in Haiti in 2010.

Because no magma is produced at conservative plate margins, we don't find any volcanic activity there.

We only find earthquake.

So really, really well done during today's lesson.

It was a pleasure teaching you and I will see you again on the next lesson.

Goodbye.