Planet Earth and Beyond
Episode 6
What’s inside the earth?
OUTCOMES
In this episode, learners will
Identify that…
 The earth has three distinct layers – the crust, mantle and core
 The earth’s crust, or outer layer, is like a skin
 The continents are part of the crust under the sea (to dispel misconception
that the continents float separately in the water).
 Most of the earth’s surface is water.
VOCABULARY
Earth’s core (the central section of the earth)
Earth’s mantle (the section of the earth between the core and the crust)
Earth’s crust (the outer layer of the earth)
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Segment 1: Introduction
POSE QUESTIONS ABOUT THE EARTH… DEVELOP CURIOSITY
Learners pose questions about the ‘earth’… What is actually under my feet?
What lies deep within the earth? I want to know how far I would have to drill to
reach the centre of the earth? Could we make a tunnel right through the earth to
Australia? Etc.
Segment 2: The earth has several layers
USING AN APPLE TO EXPLAIN THE EARTH’S LAYERS
Let’ use an apple to help us understand some of the things about the earth that
we cannot see.
The earth having three layers, as follows:
The outside layer – on which we are standing – is called the crust.
Facts: In comparison to the thickness of the core and the mantle, the crust is a
much thinner layer of rock. Look at the skin of this apple – it is much thinner than
the core or the white fleshy part. The crust of the earth is like the skin of the
apple – the same relative thickness.
(Additional facts: the crust makes up less than one-hundredth of the earth’s
weight. Under the sea, the crust is about 7kms thick and under the continents it
is somewhere between 35 and 70 km thick.)
The second layer is called the mantle – like the white, fleshy part of the open
apple). Parts of this layer are also very hot and, in places, the rocks have melted
to become like thick, hot toffee.
(Additional facts: The mantle makes up just a bit less than three quarters of the
earth’s weight. It is about 2900kms thick.)
Question: But that’s so scary! If we tread too hard, will we break through the crust
and fall into boiling hot toffee? Answer: No! Although the earth’s crust is very thin
in comparison to the thickness of the core and the mantle, it is between 6 and 70
kilometres thick, and the thick bits are the land (yes!). So no fear that we will fall
through!
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Just as the apple core is at the centre of the fruit, so the earth’s core is at the
very centre of the earth (core of the apple). This core is made up of minerals (iron
and nickel) which are extremely hot – so hot that in some places they have
melted to form a liquid.
(Additional facts: The core makes up about one third of the earth’s weight. The
inner core is thick and solid while the outer part of the core is thick and liquid.
Altogether, the core is about 3500 km thick. The kids could be asked to think of
equivalent distances e.g. about 3 trips between JHB and CT.)
(Additional possible question: How far would I have to drill to get to the centre of
the earth? Answer: The deepest hole that has ever been drilled into the earth’s
crust is 13 kilometres deep. To reach the centre of the earth, you would have to
drill about 500 times deeper. Can you work out how deep that is? (6500kms).)
Finally use graphic to illustrate… GRAPHIC: CROSS-SECTION OF THE EARTH
SHOWING CRUST, MANTLE AND CORE
Segment 3: A closer look at the earth’s crust
LOOK AT A GLOBE…
Since we live on the earth’s surface or upper part of the crust, let’s focus a bit
more on the crust itself. Is it smooth like an apple? No, it is very wrinkled, there
are lots of mountains. Just as well otherwise the earth would be covered with
water, about 4 kilometres deep.
Show the globe again and ask someone to point out the land and sea masses.
Ask: Can you estimate how much of the earth’s crust is covered by water?
Answer: About 70%
Question: So what is under the sea? (It is a common misconception that the
crust ends where the continents end!) Answer: The crust covers the whole globe
so there is crust under the oceans. The bottom of the sea is not flat, there are
also mountain ranges under water!
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Segment 5: Components of the Happy Hippos’ song


The earth has three layers: the core at the centre, the mantle and the crust.
The earth’s crust is thin in comparison to the other layers.
Task…
Draw a representation of the earth, cut in half (cross-section).Label the three
parts… core, mantle and crust.
Link…
In the next episode we continue to explore the earth’s crust.
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To be explored in Print Materials… (Taken out of script because of time
constraints etc.)
The plates ‘ride’ or ‘sit’ on soft, partly melted rock which moves underneath them.
As the pieces push against each other, all sorts of spectacular things happen –
like earthquakes and volcanoes.
Practical experiment:
Ask learners to pretend that their hands are plates of the earth.
They press their hands together tightly, with their two index fingers pressed
against each other and their thumbs tucked away.
Let them experiment with the different ways in which their hands might move in
relation to one another.
For example, one hand might push itself into a position slightly over the other; or
one hand might move ahead of the other; or the pressure of the two hands might
be so great that the index fingers collapse inwards, causing the upper hands to
bend where they join and create ‘mountains’ on their outer sides; or the hands
might separate.
These are all ways that show how the plates or segments of the earths crust
move.
Recap (Another activity to see how the earth’s crust moves)
You will need:
A length of light foam/spongy matting (like a yoga mat or a groundsheet – even
a material mat that will easily bend when pushed from the sides would do)
Two smaller mats or pieces of foam (see picture provided)
What to do: (see pics provided)

Let a child push the long mat together from its edges to show how mountain
ranges can be made from movements in the earth’s crust.

Another child can show how one ‘plate’ can slide under another, where it is
pushed down into the mantle and melts.
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
A child shows how two plates can split apart and melted rock can bubble up
to fill the gap.

Let a child show how sometimes two plates slip sideways past one another.
This movement can cause earthquakes.
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