Hello, my name's Mrs. Niven, and today, we're going to be looking inside rock as part of our topic on earth's resources.

Now, many of you will have experience of rocks, whether that's in your garden, down the path, down the driveway, or perhaps on holiday.

But what we'll learn in today's lesson will help us to better describe what we see in rocks and the information we can get from them as we try to answer that big question of how can we explain changes that we see in the air, the land, and the oceans.

So, by the end of today's lesson, you should be able to make some detailed observations of different rocks, but more importantly, use some key terms to describe the features that you find within them.

Now, throughout the lesson, we'll be using some of those keywords that we'll hopefully be using in our descriptions, and they include grains, crystal, texture, mineral, and interlocking.

Now, the definitions for these keywords are found in sentence form on the next slide, and you may wish to pause the video here, so that you can read through them or perhaps make a note of them before continuing.

So, in today's lesson, we'll be looking at three main things.

Firstly, we'll be looking at the features that we might find within rocks.

Then, we'll move on to how we can use those features to describe rocks.

And finally, we'll look at how scientists might use rocks to tell geological time.

So, let's get started by looking at the features of rocks.

Now, we can see from this picture that there are many types of rocks.

Some of them look quite speckled, whilst others might be coloured and highly polished.

Some look rough whilst others look very flat and thin.

Now, all of these then are features and they help us to tell one rock from another.

But the features of these rocks are actually determined by what's inside of them.

So, let's take a closer look.

Now, if we pick up any rock, we may be able to see one or more of the following things in it.

We might be able to see seashells or perhaps even a fossil if you're really lucky.

You will probably be able to see grains and you might be able to see some that have crystals.

Now, it's really important we understand the difference between a grain and a crystal.

A grain are the individual pieces that make up a rock and they can be lots of different sizes.

So, the larger grit pieces or even larger than that may be pebbles.

And then, you have the smaller pieces of sand.

Crystals on the other hand, are solids whose particles have an arrangement that's very, very ordered.

And because of that, their shapes are very regular and they tend to have very flat or sharp edges to them.

Now, whilst it's important to understand the difference between a grain and a crystal, it can actually be quite tricky sometimes to identify which is which inside a rock.

So, we need to be using a magnifying glass of some sort or perhaps a hand lens.

I have seen some people actually use the camera on a phone, a mobile phone if you have, and zoom in as much as you possibly can.

Whatever you need to do is make something that looks at the rock and makes what you're seeing a little bit larger.

And when we do that to these two rocks, we can see that the one on the left would contain crystals whilst the one on the right contains grains.

Let's pause here for a quick check.

Which of these might you find inside a rock? You may wish to pause the video here, so you can discuss with your neighbour what you think, and then come back when you're ready to check your answers.

Well done if you said all of them, you'd be exactly right.

Seashells, fossils, sand, grit, crystals, any of those you might be able to find inside of a rock.

So, well done if you got them all right.

Time for our first task.

Now, what I'm gonna ask you to do is to find a selection of rocks and you're going to need a magnifying glass of some sort.

You're going to then use the magnifying glass to examine those rocks and see what you can find within them.

And I'm going to ask you then to record your observations in a table and I'll give you an example of that in a moment.

But first of all, the rocks and your magnifying glass.

Now, if you're at school, these are probably gonna be provided for you.

But if you're at home and you're like me, perhaps you have collected rocks along some of your travels that you've done on.

You could just use any of those.

In terms of a magnifying glass, now I actually carry a pocket magnifying glass with me sometimes, so I can use this.

You can see there's even a light on it that helps me to see things a little bit easier.

Failing that, maybe you have a compass lying around.

There's actually a magnifying glass in there that you could use.

But do what you can.

You may not know the name of these rocks if you're using the rocks that you have at home, that's absolutely fine.

But what you may wanna do is just draw a quick sketch, maybe do a little bit of colouring in there as well, so that you can refer back to it later.

But just try and keep track of which rock you're looking at, so you can keep track of the features that you're finding within it.

Now, I did say I'd like you to record these observations.

So, like any good scientist, you'll be recording these in a very ordered way.

So, I have a table here that I'd like you to record your results in.

Now, if for some reason you don't have any access to rocks either at home, in your neighbourhood, or perhaps you don't have access to a magnifying glass that might help, that is absolutely fine.

I have for you here some other examples that you could use.

And whilst you may not be able to know the name, that's absolutely fine.

As I said, can you perhaps write down some observations of the pictures that we see here about what you can find within these rocks? So, pause the video now and have a go at completing the task and we'll come back and check your work in a moment.

Okay, let's see how you got on.

Now, it's gonna be rather difficult to provide feedback on rocks that you've used either at school or that you found at home on your own.

So, I'm going to provide feedback on this alternative task where you were provided with some example rocks.

And have a look and see what I've included in my observations to see if perhaps you included something similar or could include some of these types of observations in your own recordings.

So, let's have a look.

So, the very first one I'm gonna look at is in the top left-hand side here.

And what I can see is that there are two different colours within this rock and that makes me think that perhaps there are two different types of grain.

Now, that's why I've put a little question mark there to just say, hmm, I'm not quite sure, but it's possible there are two different types of grain.

Moving down to the image below, I think I can see some bits of shell to the left and middle left of that picture.

And I think as well that it looks like it might have some grains, because it doesn't look like there's any sharp edges.

They look a little rounded there.

In the bottom left-hand picture, I think there might be crystals here, because it looks a little bit sharper.

And again, I see two different colours.

So, perhaps there are two different grains.

And I'm not sure, so I've included a question mark there.

Moving over to the top right, I think I can see a fossil with those little circular indentations within the rock, but it all looks to be one colour.

So, perhaps it is just one grain that is visible here.

Moving down to the middle right picture, I think again that I'm not seeing any sharp edges here.

So, perhaps there are grains, but there might be some crystals, 'cause there seems to be a little bit of a bright spots.

I'm not sure.

So, I probably should have included some question marks on that one.

And on the bottom right-hand picture, I think there are definitely crystals here.

We've got some really sharp edges and we definitely have two different colours, so there's possible for two different grains.

So, you can see here that what I'm looking for are some very distinct features like the shells and the fossils, and then looking at how many different colours can you see in that rock.

Perhaps that gives an indication of how many grains there are within that rock as well.

So, not an easy task.

Hopefully you were able to use that magnifying glass to some good degree and we're able to get a few of those features out of the rocks that you looked at.

It's very well done.

Now that we're feeling a little bit more confident being able to identify features within rocks, let's look at how we might be able to use them to describe those rocks.

Let's go back to that image from the start of the lesson.

How might you describe these rocks? Now, some of you may have thought that the one in the top left looks a little blocky.

You may have mentioned speckled, like I mentioned earlier.

This one on the top right looks a bit layered perhaps, a bit gravelly.

Then, we've got in the bottom left, we definitely see some different colours of rocks in this particular image.

And we might be saying that they're a bit polished.

And in the bottom right, you might've said that they were very thin and very flat, very dark in colour, things like that.

Now, whilst describing a rock based on its colour or its shape, then that works, but a better way to describe a rock is actually by its texture.

Now, a rock's texture actually describes more importantly the grains that we find within that rock, it's shape and the size of those grains.

And it also describes how those grains are arranged within the rock.

And it's a rock's texture then that is going to give us those clues we need to decide how was this rock actually formed in the first place? So, let's take a closer look at how we might be able to describe the texture of a rock.

Now, we already know that some rocks contain grains.

Now, grains are usually particles of sediment or bits of rock.

Now, the grains could actually have some gaps between them, and you can see that, because you can actually see tiny little holes.

Or actually if you were to rub your finger across a rock, sometimes the little pieces break off.

And that happens, because you're able to put enough force within those gaps and it just breaks a piece off of it.

Some of these grains don't have gaps between them.

And grains that don't have gaps between them are known as interlocking grains.

They don't have any gaps between them.

And when you rub your finger across them, those grains don't come off as easily.

Now, some other rocks may contain crystals.

And we mentioned earlier that crystals have a regular arrangement of particles and they've got a sharp shape to 'em, possibly some sharp edges.

Now, these crystals then could have their arrangement be rather random.

So, they're all over the place and they tend to have rocks that look quite speckled.

Other crystals then might be aligned.

Now, what we mean by that is that they're actually in line with each other, and you can see it quite clearly in the picture here on the bottom right, that we have what looks like layers.

You can actually clearly see the alignment where they've just lined up one after the other to give us those lovely layers.

Let's pause here for a quick check.

True or false, grains with gaps between them are described as interlocking grains.

Well done if you said false, but which of these statements helps to say why? Well done if you said B, interlocking grains contain no gaps between them, and anything with a gap is not interlocking.

Inter means between and locking means keeping 'em together.

So, if there's nothing between our grains keeping them together, it's not interlocking.

Well done if you got that correct.

Let's try another one.

Which combination or combinations of grains or crystals are common in rocks? A, B, C, or a combination of them? Well done if you said all of them.

You could have grains only in your rock, you could have crystals that are all jumbled about in your rock, or you could have just crystals that are all lined up within your rock.

So, well done if you managed to get that correct.

Let's have a go now to bring together everything we've learned about identifying the features, and then now describing the texture of a rock.

Now, rather than using in a rock with a magnifying glass, which sometimes doesn't give you as much detail, we're going to use some diagrams instead.

So, I'm gonna do an example first.

And I've got a picture here.

And we can see that the light green bits around these circles is actually salt crystals that have filled the gaps.

So, using some of my key terms, I might describe the texture for this particular rock diagram as showing rounded grains, because I can see these circles.

I can see that they're interlocking, because there aren't any gaps.

They've been filled with those salt crystals.

I could also say that they're all the same-sized grains, because we can see that not one is larger or smaller than the other.

They're all about the same.

And I could maybe say that there's only one mineral and that they're all the same mineral, because they're all the same colour and the same size within this diagram.

So, I've done an example here trying to describe the texture of a rock.

What I'd like you to do now is to have a go at describing the texture of this rock.

Now, you may want to pause the video here, so that you can have a chat and a think, and then come back when you're ready to check your answer.

Okay, let's see how you got on.

Now, the first thing I can see when I look at this rock diagram is that I've got some square and rectangular shapes, and they look like they have some sharp edges to them.

They're quite regular.

That gives you that square rectangular shape.

So, I'm gonna say these are crystals and not grains.

So, I've given you the shape and I've said that they're crystals that are in there.

They're definitely interlocking, because when I look closely at them, there aren't any gaps between those crystals.

I can say as well the different sizes of those crystals.

I've got some very small pink ones, the white square crystals, and then the larger rectangular grey crystals that are there.

And I can see as well that we have three different colours.

So, that gives me an indication we probably have three different minerals within this rock.

So, well done if you've got even just one or two of those descriptions of the texture.

And incredibly well done if you've got three or four.

Well done, guys.

Let's move on to the next task in today's lesson.

So, for the first part, I'd like you to please match up each keyword to its correct description.

Pause the video here and come back when you're ready to check your answers.

Okay, let's see how you got on.

So, a grain are actually the pieces that make up a rock, whereas a crystal is a solid that has a very regular shape to it.

Minerals are known as the building blocks of rocks.

And interlocking means that something does not have gaps between those grains.

A texture then describes the shape, the size, and the arrangement of the grains within a rock.

So, very well done if you manage to match up each keyword to the correct description.

Okay, for the next part of this task, what I'd like you to do is to practise describing the texture of the rock diagrams below.

And I've given you some suggestions of what you might want to include in your description.

So, think about the shape of the grains or crystals and whether or not they're interlocking.

Maybe consider the relative size or sizes of those grains.

And then, think about how many different minerals that rock might contain.

Now, this is gonna take a little bit of time and you might want to discuss your ideas with the people nearest you.

So, definitely pause the video here and come back when you're ready to check your answers.

Okay, let's see how you got on.

So, for diagram A, I would've said that we definitely have rounded grains, but they are non-interlocking.

I cannot see anything that is in the space between these grains, and so they are not interlocking.

I definitely can see three sizes of the grains.

We've got the small pink ones, the slightly larger blue ones, and then the very large green ones.

And I've got three different sizes, three different colours, and therefore probably three different minerals.

So, well done if you've got at least two of them and fantastic work if you manage to get all three.

So, moving on to diagram B then.

I can see that these are square and rectangular and they've got sharp edges, so they're probably crystals.

And I can also see that they are aligned.

So, we've got all of the grey ones kind of top and bottom, and then the alternating blue and white ones in the centre.

So, they've all lined up into a layer.

I have small and medium-sized crystals here.

And because I have three different colours, I probably have three different minerals.

So, incredibly well done if you managed to get at least two or three of them, and fantastic work if you managed to identify that they were aligned crystals as well.

That was a tricky one.

So, well done if you managed to do that.

Great job, guys.

You're doing great.

Okay, let's move on to the last section in today's lesson, looking at using rocks to tell geological time.

Now, some scientists tell time using a geological timescale, but what do we mean by that word geological? So, let's try and pull that apart.

When we look at the prefixed geo, we know that it means earth, and you'll be familiar with some other words that have that prefix, things like geography.

Logic then means something's done in an orderly fashion.

And that al suffix is referring to the study of something.

So, if we bring all of those ideas together, geological simply means the study of the earth in an orderly fashion.

So, a geological timescale then represents the time based on a study of things that are found in the earth.

And we're talking about things like fossils and rocks.

So, let's look at how that's actually done.

Now, if I wanna know the time of day, I'm going to use a clock.

Now, on our clock, we have two main features.

We have the shorthand telling us the hour, and then we have the longhand that's telling us the minutes in the day.

Now, scientists use a very similar idea when they're trying to tell geological time, but the shorthand is usually one feature that they find in the earth, and the longhand is another feature that they find in the earth.

So, let's take a closer look.

Like the shorthand on a clock can tell us the hour, fossils can help us to identify a general relative geological time period, what's known as an era.

So, if we look at this fossil of a footprint, in our geological timeline, which is shown in a diagram on the right here, we could see that it fits into this zone, and therefore the era is the Cenozoic era.

If we look at a different fossil here, trilobyte, it's found in a different section of our timeline, and therefore the era is the Paleozoic era.

Now, just like the minute hand on the clock can give us a better understanding of where exactly in the hour we are, are we a quarter past, half past? Is it 10 minutes to the hour? Minerals in the earth and where we find gives us a more accurate geological timeframe.

It gives us what's known as an epoch.

So, it's these sections that we're looking at.

Now, this particular analysis and study of the earth is really useful when we're looking at rocks that don't contain fossils.

And we're also able to then identify where in the timeline we might find rocks that contain crystals.

And if we look closer at these epochs, you can see that some of these names might be a little bit more familiar to you when we're talking about geological time, something like the Jurassic time zone or the Cretaceous time zone.

So, these are probably parts of geological time that you're more familiar with.

Let's take a quick pause here to check to see how you're getting on.

True or false, the most accurate geological time is found by examining fossils.

Well done if you said false, but which of these statements best justifies your answer? Well done if you said B, mineral analysis helps us to date those rocks that don't contain fossils or for those that are composed of crystals.

So, very well done if you manage to get those correct.

Okay, let's move on to the last task of today's lesson.

What I'd like you to do is to use the geological timescale that's here on the right to help you answer the questions below.

You may wanna pause the video here, and then come back when you're ready to check your answers.

Okay, let's see how you got on.

So, the first question was for you to decide which is the younger epoch.

Is it the Triassic or the Jurassic? Now, if we find those in our geological timescale on the right, we would be able to see that the Jurassic is the younger epoch, because it is found above the Triassic.

And when you compare the numbers to the right of where we can find them on our diagram, it's 200 million years ago is the Jurassic period, but 250 million years ago is the Triassic, so that makes it older.

The next question then was for you to list these eras in order from the youngest, sorry, from the oldest to the youngest.

So, when we use our timeline on the right, we can see that it should go from the Paleozoic is the oldest, then the Mesozoic, and then the Cenezoic.

Well done if you manage to get those in the correct order.

And then, finally, you were asked how many years apart is the start of the Cambrian and the Cretaceous epochs? So, using my diagram again on the right, I can see that the Cretaceous period started 145 million years ago whilst the Cambrian epoch started 540 million years ago.

So, if I take 540 and subtract 145, I can see that the difference between them is 395 million years apart.

Now, you can see why we might use these names to describe geological time, because if we had to keep referring to something as however many million years apart, it gets a little bit cumbersome.

But if somebody talks about a period like the Cretaceous period or the Triassic epoch, we've got a clearer understanding of just how long ago these took place.

So, very well done if you managed to read your geological time correctly.

Okay, let's move on to the last part of our last task.

What I'd like you to do is return to the rocks that you used in Task A.

And what I'd like you to do is to just think about how easy is it to tell if the rock contains those crystals or those grains.

And I'd like you to explain your answer.

Now, there's not gonna be a right or wrong answer, it's just what do you reckon? And then, what I'd like you to do is to take a closer look at those rocks that were made from grains and see if there's anything else that you see within them.

And do the same thing then for crystals, thinking about what would we need to look at to try and tell the geological time of those particular rocks.

So, pause the video here, and then come back when you're ready to check your answers.

Okay, let's see how you got on.

Now, as I said for question A about whether or not you think it's easy to tell if a rock contains crystals or grains, I don't know about you, but this is what I thought.

I think that it's actually quite challenging to try and identify whether or not a rock has crystals or grains.

And that's because they can be really, really small.

And so, the features can be a little difficult to distinguish.

They're not very clear.

So, what we might need to do is look to see if there are other features within the rocks that could indicate if it's made of grains or crystals.

So, if you compare then rocks that were made from grains, there is the possibility that you found other features.

And what I found was when I looked at rocks that have grains in them, I can normally find something else, some shells or fossils, or I can see those mixture of grains a little bit easier.

It's a far easier to discern those different colours within them, but definitely looking for fossils or shells.

So, if I find a fossil or a shell within a rock, it's more than likely going to contain grains within it.

Now, when I look at rocks that contain crystals and compare them, well, with those ones, I don't tend to find any fossil fragments or any shells within them.

So, when I find a rock that doesn't have any of those features, it's possible more than likely that it's actually composed of crystals.

So, lots of different things to think about.

Again, don't worry if you didn't manage to get these particular questions correct.

They are very difficult to try and identify within rocks, particularly if you don't have a very strong magnifying glass or if you're not used to doing it.

So, this is something that you will improve on as we go through this topic.

So, very well done though for your first attempt at it.

Great job, guys.

So, let's summarise what we've learned in today's lesson.

Well, first of all, we've learned that rocks can be composed of lots of different things, and they tend to be things like sand or different types of grains.

We've got fossils, shells, crystals, all sorts of things that you can find within a rock.

Rocks also contain grains, and those grains can be described as rounded.

They might be interlocking, things like that, or even just by their size.

Some rocks contain crystals, and those crystals can be pointing in lots of different directions, making the rock look quite speckled.

Or they can be aligned, which gives us rocks that have layers of crystals within them.

And finally, we've looked at how the composition of these rocks and their textures can help give us clues to how those rocks were formed, but also how old they might be.

And those features then help to provide some insight into the history of the earth and helps us to tell geological time.

I hope you had a great time learning with me today and to see you again soon.

Great job, guys.