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Igneous Rock formed from Magma Crystals from molten rock > silica
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Igneous RocksIgneous Rocks by Ann C. Cloutier Earth & Space Science by Ann C. Cloutier Earth & Space Science
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Igneous rocksIgneous rocks are formed from the crystallization of magma.are formed from the crystallization of magma.
can form can form on or near theon or near the surface of surface of Earth > extrusive igneous rockEarth > extrusive igneous rock
or form internally or form internally beneathbeneath the Earth the Earth surface > intrusive igneous rocksurface > intrusive igneous rock
granite is the most common intrusive granite is the most common intrusive igneous rockigneous rock
ignis is Latin for “fire”ignis is Latin for “fire” lava is magma that has flowed out lava is magma that has flowed out
onto Earth’s surfaceonto Earth’s surface
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Lava Lava && MagmaMagmaare the same except where they coolare the same except where they cool
Lava cools quickly on Lava cools quickly on the surface forming the surface forming fine grained crystals fine grained crystals
> tuff, scoria, pumice> tuff, scoria, pumice Ejected lava does not Ejected lava does not
have time to form have time to form crystals we can see crystals we can see
> obsidian > obsidian (volcanic glass)(volcanic glass) rhyoliterhyolite
Magma cools slowly Magma cools slowly beneath Earth’s surface beneath Earth’s surface and forms larger coarse and forms larger coarse grained igneous rocks grained igneous rocks
> granite pegmatites> granite pegmatites Aa and Pahoehoe are Hawaiian words
geologist use for types of lava
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Magma is a mix of Magma is a mix of gases, rock, water and mineral gases, rock, water and mineral
crystalscrystals elements found in elements found in
magma are the same magma are the same major elements found in major elements found in Earth’s crustEarth’s crust
oxygen, silicon, oxygen, silicon, aluminum, iron, aluminum, iron, magnesium, calcium, magnesium, calcium, potassium , sodiumpotassium , sodium
Silica is the most Silica is the most abundant and affects the abundant and affects the characteristics of magmacharacteristics of magma
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Three types of magmaThree types of magma
Basaltic Granitic Basaltic Granitic AndesiticAndesitic
magma characteristics vary due to magma characteristics vary due to water content and silica Si O water content and silica Si O 2 2
water and silica can affect the water and silica can affect the melting temperature melting temperature
which will affect the magma’s which will affect the magma’s viscosity viscosity (how it flows)(how it flows)
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How do rocks melt ?How do rocks melt ?
to melt rock we need temperatures ~ to melt rock we need temperatures ~ 800 * C – 1,200 * C800 * C – 1,200 * C
partial melting occurs because partial melting occurs because different minerals have different different minerals have different melting pointsmelting points
magma can have a mix of molten magma can have a mix of molten rock and unmelted rock crystals > rock and unmelted rock crystals > which explains why some crystal in which explains why some crystal in magma are larger than othersmagma are larger than others
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Pegmatite's are cooled Pegmatite's are cooled magmamagma
Gems often are found in Gems often are found in pegmatitespegmatites Gems are formed Gems are formed
under these under these conditions of slow conditions of slow cooling magma cooling magma deep undergrounddeep underground
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Geothermal Gradient Geothermal Gradient
affect the type of magma affect the type of magma formed formed
TemperatureTemperature PressurePressure Water contentWater content Mineral compositionMineral composition
The greater the pressure on the rock results The greater the pressure on the rock results in the higher the melting point will become.in the higher the melting point will become.The greater the water content results in the The greater the water content results in the decrease in the melting pointdecrease in the melting point
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Where does all the heat come Where does all the heat come from ?from ?
Heat is transferred from Earth’s core > to the mantle > on to Heat is transferred from Earth’s core > to the mantle > on to the lithospherethe lithosphere
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Fractional CrystallizationFractional Crystallization
When magma cools, it crystallizes in the When magma cools, it crystallizes in the reverse order of partial melting-the first reverse order of partial melting-the first minerals to crystallize from magma, are minerals to crystallize from magma, are the last minerals to melt during partial the last minerals to melt during partial meltingmelting
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Bowen’s Reaction SeriesBowen’s Reaction Series Canadian geologist N.L.Bowen demonstrated Canadian geologist N.L.Bowen demonstrated
that as magma cools, minerals form in that as magma cools, minerals form in predictable patternspredictable patterns
known as Bowen’s Reaction Series (BRS) known as Bowen’s Reaction Series (BRS) illustrates the relationship between cooling illustrates the relationship between cooling magma and the minerals that formmagma and the minerals that form
Two main patterns were discovered and Two main patterns were discovered and documented by Bowen:documented by Bowen:
1. a 1. a continuous patterncontinuous pattern, with gradual changes of , with gradual changes of mineral composition in the feldspar groupmineral composition in the feldspar group2. is characterized by an abrupt change of mineral 2. is characterized by an abrupt change of mineral
types types in the iron-magnesium group in the iron-magnesium group discontinuous discontinuous patternpattern
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Chart with Bowen’s ReactionChart with Bowen’s Reactiontemperaturestemperatures
magma typemagma type
http://http://
www.youtube.com/watch?v=en6ihAM9fe8www.youtube.com/watch?v=en6ihAM9fe8
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Igneous Rock FormationIgneous Rock Formationclassified by light or dark mineralsclassified by light or dark minerals
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Classification of Igneous Classification of Igneous RocksRocks
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Silica content and DensitySilica content and Density
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Igneous Rocks Igneous Rocks can be formed Intrusively or can be formed Intrusively or
ExtrusivelyExtrusively Intrusive igneous Intrusive igneous
rocks form inside rocks form inside the Earth’s crustthe Earth’s crust
Extrusively formed Extrusively formed rocks form outside rocks form outside or near the surface or near the surface of the Earth’s crustof the Earth’s crust
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Concept map of igneous rock Concept map of igneous rock formationformation
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Crystal size and cooling rateCrystal size and cooling rate the relationship of the relationship of
how large a crystal how large a crystal can become is can become is determined by the determined by the amount of time and amount of time and space allowed for a space allowed for a crystal to form.crystal to form.
small crystals cooled small crystals cooled quicklyquickly
larger crystals cooled larger crystals cooled
s l o w l ys l o w l yRare and beautiful
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Felsic < > Mafic RockFelsic < > Mafic Rock
Felsic rock such as granite, are light-Felsic rock such as granite, are light-colored and have high silica content, colored and have high silica content, contain quartz and the feldspars contain quartz and the feldspars orthoclaseorthoclase
Mafic rocks such as gabbro, are dark-Mafic rocks such as gabbro, are dark-colored have lower silica content and are colored have lower silica content and are rich in iron and magnesiumrich in iron and magnesium
Mafic rocks can contain plagioclase, Mafic rocks can contain plagioclase, biotite, amphibole, pyroxene and olivinebiotite, amphibole, pyroxene and olivine
Grain size and texture give more clues Grain size and texture give more clues when identifying igneous rockswhen identifying igneous rocks
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Texture of Igneous RocksTexture of Igneous Rocks Porphyritic texture are Porphyritic texture are
rocks with two different rocks with two different grain sizesgrain sizes
Granite is the most Granite is the most durable igneous rock durable igneous rock and is used in many and is used in many construction projectsconstruction projects
Granite has interlocking Granite has interlocking grain crystals which grain crystals which give it great strengthgive it great strength
Pegmatites have large-Pegmatites have large-grained mineral crystalsgrained mineral crystals
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Kimberlite Kimberlite There’s diamonds in them’ there hills or craters !
Diamonds can be found on Diamonds can be found on all continents including the all continents including the
USA USA
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OresOresgold, silver, copper, leadgold, silver, copper, lead
valuable ore deposits are often associated valuable ore deposits are often associated with igneous rockswith igneous rocks
must be mined for a profit $$$$$must be mined for a profit $$$$$ ores often form in the Earth when fluids ores often form in the Earth when fluids
left during magma crystallization contain left during magma crystallization contain high levels of silica and water. high levels of silica and water.
leftover elements that were not leftover elements that were not incorporated into common mineralsincorporated into common minerals
important metallic elements important metallic elements > > gold,silver,lead,copper form in metal rich veinsgold,silver,lead,copper form in metal rich veins
Mining magnetiteMining magnetite
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Most of New York’s skyscrapers Most of New York’s skyscrapers were built using granite > a strong were built using granite > a strong
igneous rockigneous rock
The EndThe End
I love the Empire State
building !