Lesson video

Hi, everyone, I'm Miss Reid and welcome to another geography lesson on mountains, volcanoes and earthquakes.

Let's look at our lesson question for today.

Our lesson question for today is, how are volcanoes formed? Well, in this lesson we're going to be learning about how volcanoes are formed.

We'll also think about different types of volcanoes and we will conclude by recapping, on where volcanoes are located around the world.

So, for today's lesson, you'll need an exercise book or a piece of paper, you'll need a pencil and you'll need your brain.

Please take a moment now, to clear away any distractions including turning off the notifications, or any apps or conversations you have running in the background if you know how to.

Finally if you can, try to find a quiet place where you won't be disturbed during the lesson.

Pause the video now, so you can get the things you need and find a quiet place to work.

Great, now you have everything you need, let's carry on.

So, we are geographers as we know, and geographers are types of scientists who study the earth and that means, the physical features, the land, for example, the mountains, and it also includes the people who live there, the human features.

Today we're going to be asking, how are volcanoes formed? We'll look at types of volcanoes, and then we'll consider by recapping on where are volcanoes formed.

So, a volcano is a mountain or hill, which has a crater and a vent.

A volcano is formed when tectonic plates collide, and one plate is pushed beneath the other.

Magma from within the earth upper mantle, works its way to the surface through a vent.

At the surface, the volcano erupts to form a lava flow, and ash deposits, and these can be in the form of gas or rocks.

Over time, as the volcano continues to erupt, it will get bigger and bigger.

In an eruption, lava rock fragments hot vapour and all gases are pushed out of the crater.

Now, volcanoes are also formed, when tectonic plates move away from one another, to produce volcanoes.

Remember, in the last slide we saw that volcanoes are formed sometimes when two plates collide.

In this case, we're looking at volcanoes being formed when two plates move away from each other.

And in this case, we're thinking about two oceanic plates.

Now in this case, hot magma rises from the mantle, travels to the Earth's surface through a vent at mid ocean ridges.

They push the plates apart.

The lava cools onto the surface of the ocean to form rock.

Over time, with more and more eruptions, the volcano rises above the surface of the water, to form islands.

Once above the surface, lava, rock fragments, hot vapour and all gases are pushed out of the crater.

So, here is a task.

Volcanoes are formed.

You need to choose two of these options so, look very carefully.

volcanoes are formed.

A, when tectonic plates collide, and one plate is pushed beneath the other.

B, when tectonic plates remain still.

C, when tectonic plates move away from one another.

D, when tectonic plates move around each other.

Pause the video now, and choose two of the options.

Great work, everyone, let's see how you did.

So, volcanoes are formed when? Tectonic plates collide, and one plate is pushed beneath the other, but volcanoes are also formed, when tectonic plates move away from one another.

Pause the video now, so you can tick or fix your answer.

Excellent work, let's move on.

Now, an active volcano, is a volcano that has had at least one eruption in the last 10,000 years.

A dormant volcano is an inactive volcano, that has not erupted in the last 10,000 years but is supposed to erupt again.

There are two types of volcanoes.

The first is shield volcanoes, my turn, your turn shield volcano.

Excellent.

And stratovolcano, your turn.

Let's learn a little bit more about both of these types of volcanoes.

So, here is a diagram of a shield volcano.

I did draw this myself if you're thinking, that looks like somebody's drawn it.

Well, that was me.

I am quite proud of it too.

You're going to be drawing your own diagram in a moment.

Now, a shield volcano has? A magma chamber, put your finger on the magma chamber.

The magma chamber is underneath the Earth's crust.

It also has solid layers of lava, that form the volcanoes short sides.

And this is because the lava flows slowly and further.

Put your fingers on the solid lava layers.

Great.

It also has a central crater, where the lava leaves the vent.

Put your finger on the crater, it's right at the top.

Excellent.

It sometimes has side vents, but not always.

Put your finger on the side vent that I've drawn here.

Great.

A shield volcano also has a vent through which the magma flows until it reaches the crater.

Now, it's really important to note, that when the molten rock is inside the Earth and travelling through the vent, we call it magma.

And when it leaves the crater we call it lava.

When it's inside the earth, we call it? That's right magma.

And when it leaves the crater we call it? That's right lava.

Your task now, is to draw a diagram of a shield volcano.

We call this a cross section, it's like we've cut the picture in half and we're looking at the inside of the volcano cross section.

Your turn? Cross section.

So you're going to draw a cross section of the shield volcano, and I want you to place the labels in the correct place.

So the labels are solid lava layers, magma chamber, crater, side vent, vent.

Pause the video now and put the correct labels on your diagram.

Let's check that you've put the correct labels, by going back to our last slide.

Pause the video now so you can check that your labels are in the correct place on your diagram.

Great work everyone.

Now we can move on.

So, this is an example of a shield volcano.

Now you can see it has low short sides, and the crater would be situated at the top.

This is a volcano called Mauna Kea, which is situated in Hawaii and it is a shield volcano.

So, here's a diagram that I've drawn of a stratovolcano.

It has a magma chamber underneath the Earth's crust, put your finger on the magma chamber.

It has solid layers of lava that forms steep sides, and this is because the lava flows quickly and cools quickly.

Put your finger on the solid layers of lava.

It has a central crater, where the lava leaves the volcano, put your finger on that central crater.

There are often side vents, and sometimes these form many volcanoes on the sides of the larger volcano.

Put your finger on the side vents.

Great work.

And there is always a central vent, Where the magma flows through.

Again It's important to note, that when the molten rock is inside the earth we call it magma, and when it leaves the crater we call it lava.

This is Mount Vesuvius, which is situated in Italy and it is a stratovolcano.

And you can see it has steep sides, and the crater is at the top.

So, your task is to draw a diagram of a stratovolcano, and place the labels in the correct place.

Pause the video now, so you can draw your cross section, and place the labels in the correct place.

Well done everyone.

Let's go back two slides, so that we can see if you have labelled your diagram, or your cross section correctly.

Pause the video now so you can check your diagram is labelled correctly.

Excellent work everyone, let's move on.

So, here is a table, and in this table, we're going to be comparing some features of shield volcanoes, and some features of stratovolcanoes.

We're going to look at the cross section, we'll think about the formation of the volcano, we'll think about the height of the volcano and the style of eruption.

Let's take a closer look.

So, there is our cross section of the shield volcano.

Formation wise, lava flows easily, so a broad volcanic mountain is built up over time by repeated eruptions.

Height, short with sides that are not steep.

Style of eruption, liquid lava emitted from a central vent.

Now let's think about stratovolcanoes.

That's the cross section.

Formation, lava does not flow as far, many layers of hardened lava build up a steep volcano after repeated eruptions.

So, the difference between those two, is one has steep sides, a stratovolcano and a shield volcano has short sides that are not steep.

Height of a stratovolcano.

Tall with sides that are steep.

Style of eruption.

Thicker lava and explosive debris emitted from a small vent.

Great.

Now we've had a look and compared the two, you are going to do a task.

The first thing you need to do, is copy this table.

In each of the rows, for formation, height and style eruption, make sure you've got about three or four lines.

Pause the video now, and draw the table.

Great.

Now you've got your table, let's do the task.

You need to sort the statements that I'm going to show you and put them in the correct places, on the formation row.

Let's read them.

Lava does not flow as far, many layers of hardened lava build up a steep volcano after repeated eruptions.

Lava flows easily, so a broad volcanic mountain is built up over time by repeated eruptions.

Pause the video now, and sort those statements into the formation row.

Which is about the shield volcano? Which is about the stratovolcano? Great work everyone, okay.

Here are the answers.

So you can see, that the shield volcano formation, is lava flows easily so a broad volcanic mountain is built up over time by repeated eruptions, and for stratovolcano, lava does not flow as far, many layers of hardened lava build up a steep volcano, after repeated eruptions.

Pause the video now so you can tick or fix your answers.

Great.

Let's move on to height.

You need to sort these statements into their correct place in the height row.

Let's read them.

Short with sides that are not steep.

Tall with with sides that are steep.

Pause the video now, and sort these statements into the correct places in the height row.

Good work everyone, let's check the answers.

So, you can see that the shield volcano, short with sides that are not steep.

Stratovolcano, tall with sides that are steep.

Pause the video now so you can take or fix your answers.

Great, everyone.

Let's move on to the final row.

Style of eruption.

You need to sort these statements, into the correct box.

Let's read them.

Thicker lava and explosive debris emitted from a small vent.

Liquid lava emitted from a central vent.

Pause the video now, so you can sort these statements into the correct places.

Excellent work everyone, let's check that last row.

You can see shield volcanoes, liquid lava emitted from a central vent, and stratovolcano, thicker lava and explosive debris emitted from a small vent.

Pause the video now ,so you can tick or fix your answers.

Excellent.

So, now we're going to recap on where volcanoes occur and why.

We already looked at this in a previous lesson.

Now, you'll remember that the black lines on the map outline the position of the earth tectonics plates.

The map also shows the location of active volcanoes around the world and those are the red dots.

What do you notice about the location of the Earth's active volcanoes? What do you notice about them? Shout it out.

That's right, they lie along the plate lines.

Now, this is because volcanoes are formed where tectonic plates are either moving towards each other, or away from each other.

The Ring of Fire is an area where a large proportion of the world stratovolcanoes can be found.

Can you trace your finger along the Ring of Fire? Have you found it? I'll show you with my pointer.

Here we start, the Ring of Fire.

It goes all the way up here, and we're coming down here, we can see there's lots more volcanoes along this plate line.

Now of course, we call it the Ring of Fire because, volcanoes emit hot molten rock, and so because of that, we refer to that area as the Ring of Fire.

It's like a circle of very, very active volcanoes.

So, that brings us to the end of today's lesson.

A really big well done on all the fantastic learning you've achieved today.

If you're able to, please take a picture of your work and ask your parents or carer, to share it with your teacher so they can see all the fantastic things you've learned today.

And if you'd like, ask your parent or carer to share your work, @OakNational on Twitter so I can see it too.

Don't forget to complete your end of lesson quiz, and enjoy the rest of your learning today.

Bye.