Igneous Rocks

Igneous RocksIgneous Rocks

Mt. Rushmore

Half Dome, Yosemite, CA

Ansel Adams

Hawaii

IGNEOUS ROCKSIGNEOUS ROCKSSome igneous rocks form from cooled Some igneous rocks form from cooled lava that has exited Earth’s crustlava that has exited Earth’s crust

Half Dome, Half Dome, Yosemite, Yosemite, CaliforniaCalifornia

Some Igneous rocks cool from Some Igneous rocks cool from magma inside Earth and later magma inside Earth and later become exposed through become exposed through pressure, uplift, and erosion!!!pressure, uplift, and erosion!!!

IgneousIgneousThink of “igniteignite”

To light a fire IgneousIgneous rock comes from the

heatheat within EarthEarth: Geothermal

Think of “igniteignite”To light a fire

IgneousIgneous rock comes from the heatheat within EarthEarth: Geothermal

How are Igneous Rocks Classified?

How are Igneous Rocks Classified?

Igneous rocks are classified by: 1. Mineral Composition 1. Mineral Composition 2. Crystal Size (Texture)2. Crystal Size (Texture)

Igneous rocks are classified by: 1. Mineral Composition 1. Mineral Composition 2. Crystal Size (Texture)2. Crystal Size (Texture)

Igneous Rock FormationIgneous Rock FormationMost Igneous rocks form directly

from Magma which is hot, molten rock

Granite is the most common igneous rock, it cooled from magma

Igneous rocks can also form from lava

Most Igneous rocks form directly from Magma which is hot, molten rock

Granite is the most common igneous rock, it cooled from magma

Igneous rocks can also form from lava

3. First Classification of Magma:3. First Classification of Magma:Felsic

Is rich in Silica (SiO2)

Small amounts of Ca, Fe, Mg (Calcium, Iron, & Magnesium)

Slow-moving, thick= HIGH VISCOSITY (resistance to flowing)

Crystallizes to light-coloredlight-colored minerals Resulting rocks have relatively low densitylow density Felsic rocks make up the continentscontinents

Felsic Is rich in Silica (SiO2)

Small amounts of Ca, Fe, Mg (Calcium, Iron, & Magnesium)

Slow-moving, thick= HIGH VISCOSITY (resistance to flowing)

Crystallizes to light-coloredlight-colored minerals Resulting rocks have relatively low densitylow density Felsic rocks make up the continentscontinents

Rhyolite Pumice

Examples of FELSIC igneous rocks

Examples of FELSIC igneous rocks

Mafic Low amounts of SilicaSilica (SiO2) Fe and Mg rich (Iron and Magnesium) FastFast-moving, thinner= LOW Viscosity:

less resistance to flowing, more fluid Crystallize to dark-coloreddark-colored minerals Resulting rocks have relatively high high

densitydensity Mafic rocks make up the ocean floorsocean floors

Mafic Low amounts of SilicaSilica (SiO2) Fe and Mg rich (Iron and Magnesium) FastFast-moving, thinner= LOW Viscosity:

less resistance to flowing, more fluid Crystallize to dark-coloreddark-colored minerals Resulting rocks have relatively high high

densitydensity Mafic rocks make up the ocean floorsocean floors

4. Second Classification of Magma:4. Second Classification of Magma:

Mafic Igneous Rock examples:Mafic Igneous Rock examples:

Basalt (ocean floor)

Gabbro

5. Crystal Size5. Crystal Size It takes timetime to grow crystals

As magma cools, it crystallizescrystallizes

If magma cools slowlyslowly, what size crystals will form?

It takes timetime to grow crystals

As magma cools, it crystallizescrystallizes

If magma cools slowlyslowly, what size crystals will form? Large Crystals

If If MagmaMagma cools cools quicklyquickly, , small crystals small crystals will form because they have will form because they have littlelittle time time to grow.to grow.

If If MagmaMagma cools cools quicklyquickly, , small crystals small crystals will form because they have will form because they have littlelittle time time to grow.to grow.

Igneous RockIgneous Rock

Obsidian is dark in color due to iron oxides.

ObsidianObsidian cools cools so fast that no so fast that no crystals have crystals have time to formtime to formA.K.A. Volcanic A.K.A. Volcanic glassglass

ObsidianObsidian cools cools so fast that no so fast that no crystals have crystals have time to formtime to formA.K.A. Volcanic A.K.A. Volcanic glassglass

6. Igneous Rocks6. Igneous RocksIntrusiveIntrusive

Igneous rock that crystallizes below Earth’s surface, from magma

Intrusive= Inside Earth

IntrusiveIntrusive Igneous rock

that crystallizes below Earth’s surface, from magma

Intrusive= Inside Earth

Granite

Large Crystal sizeLarge Crystal sizeLarge Crystal sizeLarge Crystal size

Notice how Granite has large crystals, it cooled Notice how Granite has large crystals, it cooled slowly from magma deep beneath Earth’s surfaceslowly from magma deep beneath Earth’s surface

Igneous RocksIgneous RocksExtrusiveExtrusive

Igneous rock that crystallizes or forms at Earth’s surface, from lava

Extrusive= exited Earth

ExtrusiveExtrusive Igneous rock

that crystallizes or forms at Earth’s surface, from lava

Extrusive= exited Earth

Basalt

Small Crystal sizeSmall Crystal sizeSmall Crystal sizeSmall Crystal size

Notice how basalt has small crystals, it Notice how basalt has small crystals, it cooled quickly at Earth’s surfacecooled quickly at Earth’s surface

LavaLava is is magmamagma that has reached the Earth’s surface.

Igneous RocksIgneous Rocks

EXT-rusive EXITED

Earth

IN-trusive Formed

IN-side Earth

EXT-rusive EXITED

Earth

IN-trusive Formed

IN-side Earth

Crystal SizeCrystal SizeCrystal SizeCrystal Size

Intrusive Rock (Large Crystal Size)

Because it is inside the Earth, it cools very slowly, giving crystals time to grow

Extrusive Rock (Small crystal size)

Cools very quickly so crystals do not have time to form

Intrusive Rock (Large Crystal Size)

Because it is inside the Earth, it cools very slowly, giving crystals time to grow

Extrusive Rock (Small crystal size)

Cools very quickly so crystals do not have time to form

Composition (what it’s made of) of GraniteComposition (what it’s made of) of GraniteGranite Rock contains the Granite Rock contains the following minerals:following minerals:

QuartzQuartz

FeldsparFeldspar

MicaMica

Granite Rock contains the Granite Rock contains the following minerals:following minerals:

QuartzQuartz

FeldsparFeldspar

MicaMica

Igneous RockIgneous RockFelsic(Light Color)Continents

Mafic(Dark Color)Ocean Floor

IntrusiveCools slowly

From Magma

Large crystals

(SiO2) rich

Large crystals

Fe, Mg rich

ExtrusiveCools quickly

From Lava

Small or no crystals

(SiO2) rich

Small or no crystals

Fe, Mg rich

Igneous RockIgneous RockFelsic(Light Color)Continents

Mafic(Dark Color)Ocean Floor

IntrusiveCools slowly

From Magma

Large crystals

(SiO2) rich

Large crystals

Fe, Mg rich

ExtrusiveCools quickly

From Lava

Small or no crystals

(SiO2) rich

Small or no crystals

Fe, Mg rich

Igneous RockIgneous RockFelsic(Light Color)Continents

Mafic(Dark Color)Ocean Floor

IntrusiveCools slowly

From Magma

Large crystals

(SiO2) rich

Large crystals

Fe, Mg rich

ExtrusiveCools quickly

From Lava

Small or no crystals

(SiO2) rich

Small or no crystals

Fe, Mg rich

Igneous RockIgneous RockFelsic(Light Color)Continents

Mafic(Dark Color)Ocean Floor

IntrusiveCools slowly

From Magma

Large crystals

(SiO2) rich

Large crystals

Fe, Mg rich

ExtrusiveCools quickly

From Lava

Small or no crystals

(SiO2) rich

Small or no crystals

Fe, Mg rich

Igneous RockIgneous RockFelsic(Light Color)Continents

Mafic(Dark Color)Ocean Floor

IntrusiveCools slowly

From Magma

Large crystals

(SiO2) rich

Large crystals

Fe, Mg rich

ExtrusiveCools quickly

From Lava

Small or no crystals

(SiO2) rich

Small or no crystals

Fe, Mg rich

Igneous RockIgneous RockFelsic(Light Color)Continents

Mafic(Dark Color)Ocean Floor

IntrusiveCools slowly

From Magma

Large crystals

(SiO2) rich

Large crystals

Fe, Mg rich

ExtrusiveCools quickly

From Lava

Small or no crystals

(SiO2) rich

Small or no crystals

Fe, Mg rich

IGNEOUSIGNEOUS

FELSIC Light colored Less dense Rich in silica (SiO2) Magma flows slowly, thick Continental crust

FELSIC Light colored Less dense Rich in silica (SiO2) Magma flows slowly, thick Continental crust

IGNEOUSIGNEOUS

MAFIC Dark colored Very dense Rich in iron (Fe) and magnesium (Mg) Magma flows quickly, thin Oceanic crust

MAFIC Dark colored Very dense Rich in iron (Fe) and magnesium (Mg) Magma flows quickly, thin Oceanic crust

IGNEOUSIGNEOUS

EXTRUSIVE “exit” Magma exits the Earth before cooling Cools and crystalizes quickly Small or no crystals

EXTRUSIVE “exit” Magma exits the Earth before cooling Cools and crystalizes quickly Small or no crystals

INTRUSIVE “in” Magma cools inside the Earth Cools and crystalizes slowly Large crystals

INTRUSIVE “in” Magma cools inside the Earth Cools and crystalizes slowly Large crystals

IGNEOUSIGNEOUS

Igneous Rock LabIgneous Rock Lab Use your Igneous observations sheet Rotate independently between the 25 stations

set up around the room Start with whichever station number you are

located Round 1: You will have less than 1 minute

at each station Do not switch to the next station until told to do

so, only 1 person at at station (if you have extra time, study your notes)

Round 2: You may go back to any unoccupied station, if needed

Use your Igneous observations sheet Rotate independently between the 25 stations

set up around the room Start with whichever station number you are

located Round 1: You will have less than 1 minute

at each station Do not switch to the next station until told to do

so, only 1 person at at station (if you have extra time, study your notes)

Round 2: You may go back to any unoccupied station, if needed