KS3 Science

Independent Learning
Booklets

Earth’s Structure
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Earth’s structure
 The Earth is almost a sphere. These are its main layers, starting with the outermost:

• crust (relatively thin and rocky)

• mantle (has the properties of a solid, but can flow very slowly)
• core (made from nickel and iron)

The radius of the core is just over half the radius of the Earth. The Earth’s atmosphere surrounds
the Earth.

The Earth’s crust, its atmosphere and oceans are the only sources of the resources that humans
need.

Rocks

Rocks are solid at room temperature. They are made of grains that fit together. Each grain in a
piece of rock is made from a mineral, which is a chemical compound. The grains in a rock can
have different:

• colours
• shapes
• sizes

There are 3 types of rock you need to know about: Igneous rock, sedimentary rock and
metamorphic rocks.

Igneous rocks

Igneous rocks are formed from molten rock that has cooled and solidified.

The inside of the Earth is very hot - hot enough to melt rocks. Molten (liquid) rock is called magma.
When the magma cools enough, it solidifies and igneous rock forms.

What are igneous rocks like?

Igneous rocks contain randomly arranged interlocking crystals. The size of the crystals depends
on how quickly the molten magma solidified:
• magma that cools slowly will form an igneous rock with large crystals
• lava that cools quickly will form an igneous rock with small crystals
This means that we get two main types of igneous rock, extrusive and intrusive, as shown in the
table:

Extrusive Intrusive

Where the magma cooled On the surface Underground

How fast the magma

Quickly Slowly
cooled

Size of crystals Small Large

Obsidian and Granite and

Examples
basalt gabbro

Extrusive igneous rocks form from magma that erupted onto the surface as lava, where it cooled
quickly. On the other hand, intrusive igneous rocks form from magma that cooled slowly, deep
underground.

Obsidian has tiny crystals

Granite has large crystals

Igneous rocks do not contain any fossils. This is because any fossils in the original rock will have
melted when the rock melted to form magma.

Sedimentary rocks

Sedimentary rocks are formed from the broken remains of other rocks that become joined
together.

A river carries, or transports, pieces of broken rock as it flows along. When the river reaches a
lake or the sea, its load of transported rocks settles to the bottom. We say that the rocks
are deposited. The deposited rocks build up in layers, called sediments. This process is
called sedimentation.

The weight of the sediments on top squashes the sediments at the bottom. This is
called compaction. The water is squeezed out from between the pieces of rock and crystals of
different salts form. The crystals stick the pieces of rock together. This process is
called cementation.
 These processes eventually make a type of rock called sedimentary rock. It may take millions of
years for sedimentary rocks to form.

Examples of sedimentary rock are:

• chalk
• limestone
• shale
• sandstone

Metamorphic rocks

Metamorphic rocks are formed from other rocks that are changed because of heat or pressure.
They are not made from molten rock – rocks that do melt form igneous rocks instead.

Earth movements can cause rocks to be deeply buried or squeezed. As a result, the rocks are
heated and put under great pressure. They do not melt, but the minerals they contain are changed
chemically, forming metamorphic rocks

What are metamorphic rocks like?

Marble is formed from limestone and contains tiny interlocking grains. The layers in slate, formed
from shale, are arranged in layers. This makes slate useful for making roof tiles because it can be
split into separate flat sheets.

Metamorphic rocks rarely contain fossils. Any that were present in the original sedimentary rock
will not normally survive the heat and pressure.

Rock cycle
Tasks
1. Label the four layers of the earth and give a description of each:

crust

mantle

outer core
inner core

Magma extrusive below cooled

intrusive cools crystallises features

2. Complete the sentences below (use the words above to help you).

magma
Igneous rocks are formed when liquid hot rock (___________) comes up towards the surface. As it
rises it __________
cools crystalizes either above the surface or ________
and ______________, below the surface.

intrusive
We call igneous rocks which form above the surface: ____________ igneous rocks and we call
extrusive
igneous rocks which form below the surface: _____________ igneous rocks. Both these rocks have
features
different _____________ cooled
due to the speed at which they have ___________.

3. Draw a labelled diagram of how an extrusive rock forms:

4. Draw a labelled diagram below of how an intrusive rock forms:

5. Draw a flow diagram to show how sediment rocks are formed. Add captions to each diagram to
explain what is happening.
6. Explain why sedimentary rocks are likely to have fossils in.
Sedimentary rocks are not under high pressure nor anywhere near a volcano. Any living thing wouldn't stay close near a volcano because
…………………………………………………………………………………………………………………
the heat is too much for them to live.
…………………………………………………………………………………………………………………
…………………………………………………………………

7. Why might there be stripes seen on a cliff face?

Use the key words below to help you:

Rocks, Weathered,Wind/Plants/Acid Rain, Broken fragments (Sediment),

Transported by rivers, Deposition, Layers, Compaction, Cementation, salts, layers.

The Sedimentary
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8. How would a sedimentary rock become a metamorphic rock?

A Sedimentary rock must be under heat and pressure
…………………………………………………………………………………………………………………
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9. state whether the following are true or false. Challenge: correct the false statements.
1) Granite is a type of metamorphic rock. false
2) Fossils can be found in metamorphic rock. false

3) Metamorphic rock forms due to heat and pressure inside the Earth. true

4) Marble is a type of metamorphic rock. true

5) Metamorphic rocks contain layers. false

6) Heat and pressure chemically alter the minerals in rocks. true
7) Metamorphic rocks can only be formed from sedimentary rocks.false

10. Draw your own version of the rock cycle, labelling the arrows show what is happening:
11. complete the wordsearch below:
12. Layers of earth description sort. Match up the descriptions with the layers.
 4

live layer
eath
13. Complete the tasks below:

half
molten
smooth
feels tissue always

iron
nickel colder
hotter

layers hot
melted mixed
Type text here

heat there
hotter

6000 degrees
14. For fun…….

Make your own model of the earth from anything around the house!!!!!!!