Which of these is an igneous rock?

basalt. Basalt forms when lava cools at the surface.

Why does granite have large crystals?

the magma cooled slowly. Slow cooling gives crystals time to grow.

Which rock is made mostly from the shells of sea creatures?

limestone. Shells are calcium carbonate, and so is limestone.

What changes shale into slate?

heat and pressure. Slate is metamorphic: changed without melting.

Which pair are both sedimentary rocks?

sandstone and shale. Marble is metamorphic. It was limestone once.

A rock is dark, with crystals too small to see. Where did it most likely form?

at the surface, cooling quickly. Fast cooling at the surface leaves no time for crystals to grow. This is basalt.

Igneous, sedimentary and metamorphic rocks · Cambridge IGCSE Environmental Management

In plain words

Every rock under your feet was made in one of three ways. It cooled from something molten, it settled out as layers of grains, or it was an older rock that got cooked and squeezed. Knowing which tells you what the rock is like and what it is good for.

7 things to know

Igneous rocks form when molten rock cools and turns solid. Molten rock is called magma while it is underground and lava once it reaches the surface. Crystals grow as it cools.
Granite forms when magma cools slowly, deep underground. Slow cooling gives crystals time to grow, so granite has large crystals that are easy to see.
Basalt forms when lava cools quickly at the surface. Fast cooling leaves no time for crystals to grow, so basalt is dark with crystals too small to see.
Sedimentary rocks form from layers of sediment. Pieces of rock, or the remains of living things, are carried by water, wind or ice and settle in layers. The layers are squeezed and glued into rock.
Limestone is made mostly from the shells and skeletons of sea creatures. Sandstone is made from grains of sand. Shale is made from very fine particles of mud and clay, in thin layers.
Metamorphic rocks form when a rock that already exists is changed by great heat, great pressure or both. The rock does not melt. Its minerals rearrange into new crystals.
Marble is formed from limestone. Slate is formed from shale, and it splits into thin, flat sheets.

Worked example

A rock has large, interlocking crystals of different colours. It has no layers and no fossils. Identify the type of rock and explain what the crystals show about how it formed.

Interlocking crystals with no layers point to an igneous rock.
Large crystals take a long time to grow, so the molten rock cooled slowly.
Slow cooling happens deep underground, so the rock is likely to be granite.

Tips and tricks

Big crystals mean slow cooling underground (granite). Tiny crystals mean fast cooling at the surface (basalt).
A metamorphic rock never melted. If a rock melts and then cools, the new rock is igneous.

6 questions, about 2 minutes.

It lands in your notebook with its questions as flashcards.

Igneous, sedimentary and metamorphic rocks: 6 questions and answers

These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.

Which of these is an igneous rock?
- basalt (the answer)
- slate
- limestone
- shale
Basalt forms when lava cools at the surface.
Why does granite have large crystals?
- the magma cooled slowly (the answer)
- the lava cooled quickly
- it was squeezed under great pressure
- it formed from layers of sand
Slow cooling gives crystals time to grow.
Which rock is made mostly from the shells of sea creatures?
- limestone (the answer)
- granite
- basalt
- slate
Shells are calcium carbonate, and so is limestone.
What changes shale into slate?
- melting and then cooling
- weathering and erosion
- being dissolved by water
- heat and pressure (the answer)
Slate is metamorphic: changed without melting.
Which pair are both sedimentary rocks?
- granite and basalt
- marble and slate
- sandstone and shale (the answer)
- limestone and marble
Marble is metamorphic. It was limestone once.
A rock is dark, with crystals too small to see. Where did it most likely form?Stretch
- deep underground, cooling slowly
- at the surface, cooling quickly (the answer)
- on the sea bed, in layers
- deep underground, under pressure
Fast cooling at the surface leaves no time for crystals to grow. This is basalt.

6 questions

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Worksheet

3 questions, 7 marks. Write your answers on paper, then check them.

Igneous, sedimentary and metamorphic rocks

Cambridge IGCSE Environmental Management 0680 · 7 marks · papermunch.org

Name ______________________________ Date ______________

Describe how granite is formed.[2]
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Magma cools slowly, deep underground. It solidifies, and large crystals form.
I got this one
Describe how sandstone is formed.[3]
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Grains of sand are carried and then deposited in layers. The weight of the layers above compacts them. Minerals cement the grains together to make rock.
I got this one
Name the rock that marble forms from, and state what causes the change.[2]
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Limestone. It is changed by heat and pressure, without melting.
I got this one

Answers: Igneous, sedimentary and metamorphic rocks

1. Magma cools slowly, deep underground. It solidifies, and large crystals form.
2. Grains of sand are carried and then deposited in layers. The weight of the layers above compacts them. Minerals cement the grains together to make rock.
3. Limestone. It is changed by heat and pressure, without melting.