Igneous Rocks Rocks & Minerals Notes: Page 7. How are igneous rocks formed?
Classification of Igneous rocks
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Transcript of Classification of Igneous rocks
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Rock ClassificationRocks are divided into three main
classes based on how they form:1. Igneous2. Sedimentary3. MetamorphicEach type of rock can be further
classified based on: Composition and texture
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Composition
The chemical make up of the rock or what it is made of.
This can be minerals or other materials: shells, clay, plants, sand, pebbles
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Texture/GrainsDetermined by the grains size, shape
and position. Igneous can be fine or coarse grainSedimentary can be characterized by
observing lithified (cemented) inorganic grains, minerals, organic material, or fossil fragments. The wide range of textures common in sedimentary rocks is separated into clastic, chemical, and bioclastic (biochemical) groups.
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Texture/Grains
Metamorphic textures consist of two main types: foliated and non-foliated textures.
Texture can reveal the process that formed the rock.
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Igneous RocksIgneous Rocks
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What are they?What are they?Rock made from cooled Rock made from cooled
–LAVA, above ground or LAVA, above ground or –MAGMA, below groundMAGMA, below ground..
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ClassificationClassification
They are classifiedThey are classified in 3 ways:in 3 ways:
1.1.Texture – grain Texture – grain 2.2.Origin - where formedOrigin - where formed3.3.Mineral Composition – Mineral Composition –
made frommade from
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Grain Size Grain Size Have….Have….
SPECIAL SPECIAL NAMESNAMES
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Texture/GrainTexture/GrainCoarseCoarse Grained = large grains, cooled Grained = large grains, cooled
slowlyslowlyThink about it…. If it cools over a long time – the grains have time to get big! Think about it…. If it cools over a long time – the grains have time to get big!
Most abundant intrusive rock is GRANITE Most abundant intrusive rock is GRANITE
FineFine Grained = small grains, cooled Grained = small grains, cooled fastfastThink about it… If it cools over a short time – the grains don’t have time to get Think about it… If it cools over a short time – the grains don’t have time to get big!big!
BasaltBasalt
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Igneous Rock Formation-Igneous Rock Formation-OriginOrigin ExtrusiveExtrusive – formed ABOVE GROUND. – formed ABOVE GROUND.
It cools It cools fastfast so it has so it has smallsmall grains. grains. IntrusiveIntrusive – formed UNDERGROUND. It – formed UNDERGROUND. It
cools cools slowlyslowly so it will have so it will have largelarge grains. grains.
Laccolith
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Examples of each type of ROCKFine Grained
Basalt = Extrusive Igneous rock
Course Grained
Granite = Intrusive Igneous rock
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Lighter
Darker
Big Crystals Small or No Crystals
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Mineral CompositionMineral Composition How much silica is in the magma/lava?How much silica is in the magma/lava?
– Low silica content = dark colored = MaficMafic
– HighHigh silica content = silica content = light light colored = colored = Felsic
High Silica Content Low Silica Content
Felsic Igneous Rock Mafic Igneous Rock
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Label the igneous rock Label the igneous rock formationformation
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Ticket out: CHOOSE ONLY Ticket out: CHOOSE ONLY ONEONE
What makes up the grains in an igneous rock?
Illustrate grains of an igneous rock and explain why this happens
Compare and contrast intrusive and extrusive igneous rocks