Lesson video

Hi, geographers.

My name's Ms. Hoggett, and I'm really excited you're here to learn some geography with me today.

I'm sure if you try your best, you're going to be absolutely fantastic.

Don't worry too much if you haven't studied this topic before, I'm here to help you every step of the way.

(indistinct) Of today's lesson is The geology of the UK and this sits within the unit Rocks, weathering, and soil: why is geology important? Our learning outcome for today is that I can explain the formation and distribution of rocks in the UK and understand how past tectonic activity shaped the landscape.

To help us through today's lesson, there's a number of keywords that are going to be really useful to us.

Igneous, sedimentary, metamorphic, tectonic, and distribution.

Our first one, igneous, is rocks formed from cold magma and lava.

Sedimentary are rocks formed from layers of compressed sediment.

Metamorphic are rocks formed due to intense heat and pressure.

Tectonic is the structure of the Earth's crust and how it was formed.

And distribution is how something is spread out over a geographical area.

So, igneous, sedimentary, metamorphic, tectonic, and distribution are going to be really helpful to us in today's lesson.

This lesson is split into two learning cycles.

The first one, rock types and their distribution in the UK, and the second, the UK's geological history.

We're going to start with the first one now, rock types and their distribution in the UK.

The Earth's crust is made up of three types of rock.

We can see the crust outlined there on the diagram of the structure of the Earth.

The crust sits around the outside of the mantle, and the mantle surrounds the outer and the inner core.

The three types of rock are igneous, sedimentary, and metamorphic rock.

Igneous rock is formed when molten rock called magma went inside the Earth or lava went on the Earth's surface cools down and solidifies.

So, we have magma there because it's under the surface and lava because the molten rock is outside the surface of the Earth and we know that lava cools down on the surface and solidifies.

There are two different types of igneous rock.

We have intrusive igneous rocks which forms inside the Earth when the magma cools slowly underground and there's extrusive igneous rock, which forms on the surface when the larva erupts from a volcano and cools quickly.

Igneous rock generally contains crystals and the size of these depends on how quickly the rock cooled down.

When we have slow cooling, we have large crystals, such as what we see in granite.

And when we have fast cooling, we have small crystals, such as what we see in basalts.

Where there's very fast cooling, there may be no crystals and it may have a glassy texture, such as obsidian.

Igneous rocks are very hard and durable.

They don't break down easily and they do not contain fossils.

The high heat destroys any living material, and some examples of igneous rocks can include granite, basalts, and obsidian, and igneous rocks help to shape landscapes and are important in the construction of natural land forms. Our sedimentary rock is formed where layers of sediment are compressed and compacted over time.

In the diagrams in the first one on the top left, we can see that we have sediment being eroded and transported.

Then in our second diagram on the right of that, we can see that the sediment is being deposited.

Then on the third diagram in the bottom left, we can see that we start to see those layers of sediment being compressed.

And then in our final diagram, we can see that those layers are being compacted over time.

So, this is how sedimentary rock is formed.

Examples of sedimentary rock can include sandstone, which is made from compacted sand and often used in buildings.

Limestone made from shells and marine organisms found in caves and on cliffs.

And shale form from mud and clay, and that can be split into thin layers.

Sedimentary rocks are really important for understanding Earth's history because they contain fossils and show how landscapes have changed over time.

Now, the last of our three main types of rocks are metamorphic rocks, and they are formed when existing rocks, which will be igneous or sedimentary are changed by heat or pressure over millions of years.

Now, there are different key features of metamorphic rocks.

The first one is that they form deep underground due to heat and pressure, and we can see that in our diagram, because the grey section shows where metamorphic rock is and we can see the heat coming from underneath from the molten magma, and we can also see the pressure formed by the weight of the overlying rock on top.

So, there's your heat and pressure.

They are harder and more durable than sedimentary rocks because of the compression.

They may contain crystals that have been rearranged, but they do not usually contain fossils, the heat and pressure destroy them.

Examples of metamorphic rock can include marble formed from limestone and is used in statues and buildings, slate formed from shale used for roof tiles, and schist, a tiny rock with visible crystals formed under high pressure.

Now, all of these rocks are connected by processes within the rock cycle.

We can see there that we have our three main types of rock, igneous, metamorphic, and sedimentary, and we also recognise why they're sediment and magma, and all of the arrows are indicating different processes that cause these different rocks to become connected.

For example, if we take igneous rock and heat it up, it forms magma, but if we cool that magma down, we end up with more igneous rock.

If we then erode or weather that igneous rock, we end up with sediment, but if we compact or cement that, we get sedimentary rock, and once we erode that sedimentary rock, we end up back at sediment.

If we go back to sedimentary rock and apply heat and pressure, we know we end up with metamorphic rock, but if we then erode or weather that metamorphic rock, we end up with sediment.

Alternatively, if we apply heat to metamorphic rock, we end up with magma.

So, we can see that all of those rocks are connected through different processes within the rock cycle.

Let's check your understanding so far.

So, which type of rock is formed due to layers of sediment being compacted and compressed over time? Pause the video and have a go answering this question.

Well done if you said b, sedimentary.

We know that igneous rock is caused due to volcanic activity, metamorphic rock is formed due to heat and pressure, but sedimentary rock is where sediment is compressed and compacted over time.

Good work, geographers.

So, these different types of rock are distributed unevenly around the UK.

So, the map we're looking at here covers just Great Britain, because it's only looking at England, Wales, and Scotland.

Distribution refers to how something is spread out over a geographical area.

So, on the screen, we can see that we have a map and this uses different colours to show where the different types of rock are found.

Where we have our yellows, our greens, our blues, our dark pink, and our purples, we can see we have sedimentary rock.

Where we have our light pink, we have metamorphic rock.

And where we can see red, we've got igneous rock.

Now, igneous rocks are found mainly in upland areas of Scotland, northwest England, North Wales, and Northern Ireland.

For example, we can see that there are areas of igneous rock in the Lake District and Snowdonia.

However, igneous rock can also be found in southern regions, such as on Dartmoor in the southwest of England.

Now, igneous rocks tend to create mountainous landscapes because they're more resistant to erosion, meaning they can erode more slowly than other nearby rocks.

On the image there, we can see we have the Cat Bells in the Lake District.

Lake District.

The Ennerdale and Eskadale granites are good examples of igneous rocks.

We can also see granites, another type of igneous rock, found in various areas of Snowdonia.

So, we can see that there are some really well-known examples of different types of igneous rocks found around Great Britain.

Metamorphic rocks dominate the highlands of Scotland, but are also commonly found in Northern Ireland.

I appreciate that Northern Ireland isn't on that map, 'cause this is just of Great Britain, but it's also worth noting that they are found there.

However, metamorphic rock can also be seen in southern regions, such as in Devon and Cornwall.

Now, what this shows us here is that actually we can see different types of metamorphic rock in areas of Cornwall and in areas of the Scottish highlands.

So, we have some really key examples listed on the screen.

Lastly, sedimentary rocks are typically found in lowland areas of England.

For example, the White Cliffs of Dover are made of chalk and they are found in the low-lying areas in the southeast of England.

Sedimentary rocks are often less resistant, meaning they're erode faster, so they tend to lead to flatter land.

And what we've got here is our two maps, and the one on the right is showing the height of the land, and we can see that where we have are lowlands, we can see that we've also got lots of sedimentary rock if we compare the two maps.

So, let's check your understanding.

the Lake District and Snowdonia contain examples of which type of rock? a, metamorphic, b, sedimentary, or c, igneous.

Pause the video and have a go at completing that question.

Well done if you said c, igneous, you're absolutely spot on.

Good work, geographers.

Which type of rock dominates Scotland's landscape? Is it a, metamorphic, b, sedimentary, or c, igneous? Pause the video and have a go answering that question.

Well done if you said a, metamorphic, you're doing a really good job.

And lastly, lowland areas of England are dominated by which type of rock? a, metamorphic, b, sedimentary, or c, igneous.

Pause the video and have a go at that question.

Done if you said b, sedimentary.

Absolutely fantastic.

So, we're now going to practise what you've learned so far.

And for this practise task, we have two parts.

For the first part, I'd like you to summarise how each rock type was formed in one sentence for each.

And then for the second part of this task, I'd like you to complete the key, identifying which colours represent which types of the three main rocks.

Off you go, pause the video, and complete this task.

Well done for giving that a really good go, geographers.

Let's check your answers.

So, for part one where you had to summarise how each rock type was formed in one sentence for each, you could have said, "Igneous rock is formed due to the cooling of molten rock, magma or lava." "Metamorphic rock is formed due to intense heat and pressure.

"And sedimentary rock is formed when sediment is compressed and compacted over time." And for part two, we had to complete the key, identifying which colours represent which of the three main rock types.

We should have had sedimentary where we had lots of colours.

And then for the light pink, we should have had metamorphic.

And igneous, we should have had the red.

Well done if you got that.

Spot on.

We're now ready to move on to learning cycle number two, the UK's geological history.

The Earth's crust is made up of large slabs called tectonic plates.

There are seven major plates and several smaller ones that cover the Earth's surface.

The UK is in the Eurasian plate, and this plate is surrounded by the North American plate, the African plate, and the Indo-Australian plate.

These plates move very slowly and have changed position over time.

They move about as quickly as our fingernails grow.

When these plates collide, pull apart, or slide past each other, they create powerful natural events like earthquakes and volcanoes.

For example, the Pacific Ring of Fire is an area with lots of volcanic eruptions and earthquakes caused by plate movement.

Aisha says, "The tectonic plates fit together like a puzzle." And this is helpful to know, because it explains why the continents seem to fit together like how South America and Africa have matching coastlines.

Scientists use this idea to support the theory of continental drift, showing that all the continents were once joined in a super continent called Pangea and have drifted away from one another.

Now, the UK has not always been in the same place.

It was once near the equator covered by tropical seas.

It has since moved further north due to continental drift.

And you can see that on the diagrams we have on the screen from the Permian to the Triassic, Jurassic, Cretaceous, and Quarternary periods, we can see that the UK has started to move further north.

Some of the UK sedimentary rocks formed when it was covered by tropical seas.

For example, the limestone cliffs in Derbyshire formed during the Carboniferous period around 330 million years ago when the land was a coral reef in a tropical lagoon.

On the screen, you can see an image showing High Tor in Matlock Dale in the Peak District.

True or false? The UK has always been in the same position.

Pause the video and have a go at answering that question.

Well done If you said false.

We know that the UK was once near the equator.

It has since moved further north due to continental drift.

Now, during the Paleozoic era, the region that is now the UK was close to a plate boundary, meaning it's experienced Earthquakes and had active volcanoes.

Mount Snowden in North Wales is made of volcanic rocks that come from volcanic eruptions around 450 million years ago.

These are mostly rhyolites and tuffs, which are examples of extrusive igneous rock.

We're going to watch the video now, which shows us the aerial view of Mount Snowden.

Dartmoor's tors are made of granite, and these were formed during the Carboniferous period when molten rock solidified underground, so intrusive igneous rock.

Over time, the surrounding rock was eroded and weathered away, exposing the granite.

Tectonic activity also pushed up mountain ranges in Scotland, Wales, and Northern England.

Whilst they've gradually worn down due to weathering and erosion, some remnants can be seen in places.

True or false? There was once volcanic activity in the UK.

Pause the video and have a go at answering that question.

Well done if you said true.

We know that the UK used to have active volcanoes.

Over millions of years, layers of sediment accumulated and were gradually buried deep beneath the Earth's surface.

As these sediments became compacted, they formed sedimentary rocks such as mudstone.

In certain regions, including what is now North Wales, immense geological forces cause the Earth's crust to shift, resulting in heat and pressure being applied to these rocks.

This process, known as metamorphism, gradually transformed the mudstone into a slate, a fine-grained durable rock with the distinct layers that make it ideal for quarrying, and an example of a metamorphic rock.

Penrhyn Quarry, located in North Wales, is one of the most significant slate quarries in the world.

During the Cambrian period, over 500 million years ago, the landscape was covered primarily by mudstone, which had formed from a compacted clay-rich sediment deposited in ancient seas.

Over time, tectonic activity subjected these rocks to extreme conditions, altering their mineral composition and structure.

The results was a high quality Cambrian slate, prized for its strength, water resistance, and ability to be split into thin uniform sheets.

Today, the quarry remains as an important site in the Welsh slate industry, which has played a vital role in the region's economy and heritage for centuries.

Slate is still actively quarried at Penrhyn Quarry today, continuing the tradition that dates back hundreds of years.

The quarry remains one of the largest slate quarries in the world, producing high quality roofing slates and other materials used in construction.

The Welsh slate industry, including Penrhyn, was once a major global supplier.

And although production has declined since its peak in the 19th century, it remains an important part of the region's economy and heritage.

Sam says, "Did you know you can visit Zip World and fly over Penrhyn Quarry on a zip line?" Zip World's at Penrhyn Quarry offers a unique experience where visitors can soar over the vast, dramatic landscape of the quarry on Velocity 2, the fastest zip line in the world and the longest in Europe.

It reaches speeds of over 100 miles an hour and riders get a breathtaking aerial view of the historic slate quarry and the beautiful Snowdonia National Park.

It's a thrilling way to experience the site.

It combines adventure with a glimpse into the area's rich industrial past and something I would really recommend.

So, we're going to practise what you've learned in today's lesson, and I'd like you to complete the table, explaining how the UK's geological history formed the different landscapes.

So, we can see on our table we've got the location, so we've got High Tor, Matlock Dale in the Peak District.

We then have our location in Mount Snowden, and then we have Penrhyn Quarry, we've got the rock type already listed there, so we can see we have limestone, which is sedimentary, then rhyolites and tuffs, which are igneous, and then slate, which is metamorphic.

And your job is to fill in how they were formed.

So, pause the video and have a go at completing that practise task.

Well done for giving that a really good go, geographers.

I'm sure you've done fantastically.

Let's take a moment to check through your answers.

So, for our sedimentary rock, limestone in High Tor, we should have said, "The limestone was formed when the land was covered by a warm, shallow tropical sea.

The skeletons of marine organisms compacted over time." For our rhyolites and tuffs at Mount Snowden, we should have said, "They were formed due to intense volcanic activity, lava, and ash erupted from volcanoes during the Ordovician period, cooling to form the igneous rocks.

Over millions of years, the rocks were exposed by erosion." And for our final rock type, our metamorphic rock, slate in Penrhyn Quarry, we should have said, "Heat and pressure transform the mudstone, that was originally deposited during the Cambrian period, into slate." We're now at the end of today's lesson on The geology of the UK, so we're going to summarise what we've learned so far.

So, the UK has a rich and varied geology with igneous, metamorphic, and sedimentary rocks present.

England's lowland geology is dominated by sedimentary rocks, such as limestone.

Scotland's geology is dominated by metamorphic rocks with areas of igneous rock.

And in the past, Britain was very close to a plate boundary, and there was volcanic activity.

Thank you for all of your hard work today, geographers, I hope you have a brilliant day, and I will see you soon.