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What are igneous rocks?The name “igneous” comes from the Latin word for fire. Wheredo you think this suggests that igneous rocks are formed?Igneous rocks are formed in, and around, volcanoes.What are some examples of igneous rocks?basalt2 of 9pumice Boardworks Ltd 2011
How are igneous rocks formed?Magma is a type of molten rock found deep underground.Occasionally magma rises up through the Earth’s surface,causing volcanic eruptions.Igneous rocks are formed when the magma cools and solidifies. When magma coolsabove the surface,extrusive igneousrocks are formed. When magma coolsbelow the surface,intrusive igneousrocks are formed.3 of 9extrusiveigneousrockintrusiveigneousrockmagma Boardworks Ltd 2011
Properties of igneous rocksHow are the properties of igneous rocks different frommetamorphic and sedimentary rocks? Igneous rocks contain interlocking crystals that are heldtogether very strongly and make the rock hard. The crystals in igneous rockshave a disorderly arrangement. The size of the crystals dependson how quickly the igneous rocksolidifies. Igneous rocks never contain fossils.4 of 9 Boardworks Ltd 2011
Crystal size in igneous rocks5 of 9 Boardworks Ltd 2011
Crystal size in igneous rocksMagma is full of minerals that turn into crystals under the rightconditions. Magma above the Earth’s surface cools quickly,causing only small crystals to form.This is how extrusiveigneous rocks like pumiceand basalt are made.Magma below the Earth’ssurface cools moreslowly. There is time forlarge crystals to grow asthe magma solidifies.This is how intrusive igneous rocks like granite are formed.6 of 9 Boardworks Ltd 2011
What is granite?Granite is an intrusive igneousrock. It is an extremely hard rock,and contains many large crystals.Granite is found all over theworld, but is commerciallyquarried in India, Brazil, SouthAfrica and Scandinavia.Because it is so hard granite isoften used as a flooring andexterior cladding material, as wellas decorative material in worktopsin kitchens and bathrooms.7 of 9 Boardworks Ltd 2011
What is pumice?Pumice is a pale grey extrusive igneous rock, made up of verysmall crystals.It is formed when bubbles ofvolcanic gas pass throughmagma as it solidifies.Because of this, pumicecontains many air pockets,making it extremely lightand porous.These lightweight properties mean that pumice is often usedas a component in breeze-block bricks. Its rough surface alsomeans that it is useful as an exfoliating (scrubbing) tool.8 of 9 Boardworks Ltd 2011
What is basalt?Basalt is a dark glassy extrusiveigneous rock.Basalt contains very smallcrystals, and is often found innature as huge columns of rock.Traditionally basalt has beenused to make weapons, tools,jewellery and carved sculptures.Today basalt is also used in theproduction of cement and roadsurfaces.9 of 9 Boardworks Ltd 2011
3 of 9 Boardworks Ltd 2011 How are igneous rocks formed? Magma is a type of molten rock found deep undergr
