Rocks

Rocks and minerals

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A rock is a solid that is made up of one or more ​

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​ . They have no set chemical composition, meaning that even though rocks can contain the same ​

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, there is often ​

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between them.

Granite

​Igneous rocks

Igneous rocks are formed when molten rock solidifies.

The word igneous comes from the Latin word - ignis

​Three kinds of rocks

Rocks are classified based on how they are formed. They are:

Igneous
Sedimentary
Metamorphic

Word Cloud

What words do you know that start with the letters ign/igni/ignis?

Draw

Magma and Lava are two words used to describe molten rocks. Mark on the volcano where you think you would find magma.

Igneous rocks

​Igneous rocks are formed when molten rock solidifies. There are two types of igneous rock - Intrusive and extrusive

Extrusive rocks are formed lava is exposed to the air and water. Because it is above ground, it cools relatively quickly.

​Extrusive

Intrusive rocks are formed when the magma moves toward the Earth’s surface but does not reach it. The magma cools slowly over millions of years.

​Intrusive

Intrusive vs extrusive

How can you tell which is which?

As rocks cool down, they form crystals in their structure.

The slower molten rock cools down, the larger the crystals in it become. In some extrusive igneous rocks (like obsidian or pumice) , you see no crystals at all

Categorize

Options (5)

Granite forms slowly and has a coarse grained texture, with lots of crystals

Gabbro has coarse grains and visible crystals.

Obsidian is volcanic glass and has no visible crystals in it.

Basalt is an igneous rock that has a very fine grained texture. It is commonly used in building

PUmics is a rock that forms when air bubbles get trapped as it cools, forming pockets.

Organize these options into the right categories

Intrusive igneous rocks

Extrusive igneous rocks

Sedimentary rocks

Sedimentary rocks are those that have been formed by layers of sediment (smaller pieces of rock) being pressed down together so firmly that they become cemented together.

You can often see the layers of sediment in these types of rocks

Sedimentary rocks

This process begins with pieces of rock being loosened by weathering and erosion. They are gradually deposited into rivers, lakes and end up at the bottom of the sea. This process is known as sedimentation.

As the layers build and press down on the lower layers, they are compacted. Over time, water is pushed out of the layers and cementation occurs. This is when salt compounds glue (or cement) the bits of rock together so that they form a solid layer