Igneous RocksIgneous Rocks

Created By:Created By:

Mr. KreegerMr. Kreeger

Homework and Page Homework and Page References References Page References- 63-68Page References- 63-68 HW #1- 1-8 on page 68 HW #1- 1-8 on page 68 HW #2- Choose 5 Igneous rocks on HW #2- Choose 5 Igneous rocks on

the chart and list the following the chart and list the following information.information.– Color indexColor index– Dominant mineralsDominant minerals– TextureTexture– How and where it formedHow and where it formed

Table of ContentsTable of Contents

1.1. Formation of Igneous RocksFormation of Igneous Rocks2.2. Characteristics of Igneous RocksCharacteristics of Igneous Rocks

a.a. TextureTextureb.b. Mineral CompositionMineral Composition

3.3. Textures of Igneous RocksTextures of Igneous Rocksa.a. IntrusiveIntrusive

1.1. Pegmatic (Very coarse grained)Pegmatic (Very coarse grained)2.2. Phaneritic (Coarse grained)Phaneritic (Coarse grained)

b.b. ExtrusiveExtrusive1.1. Aphanitic (Fine Grained)Aphanitic (Fine Grained)2.2. GlassyGlassy3.3. Vesicular (Gas Bubbles)Vesicular (Gas Bubbles)4.4. Pyroclastic (particles from volcano)Pyroclastic (particles from volcano)

c.c. Intrusive and ExtrusiveIntrusive and Extrusive1.1. PorphyriticPorphyritic

4.4. Mineral CompositionMineral Compositiona.a. Felsic Felsic b.b. MaficMafic

5.5. How to Identify Igneous RocksHow to Identify Igneous Rocks

Introduction VideoIntroduction Video

Igneous Rock ID ChartIgneous Rock ID ChartPage 6 of ESRTPage 6 of ESRT

1. Formation of 1. Formation of Igneous RocksIgneous Rocks Form as the result of Form as the result of

cooling or solidification cooling or solidification of of Magma.Magma.

LIQUID HOT MAGMALIQUID HOT MAGMA– Mixture of hot liquid Mixture of hot liquid

rock, gases and crystalsrock, gases and crystals– Less denseLess dense than than

surrounding rock so it surrounding rock so it moves upwardmoves upward

Magma that Magma that reachesreaches surfacesurface (lava) erupts and (lava) erupts and solidifies- solidifies- Extrusive IRExtrusive IR

Magma that Magma that cools cools underground-Intrusive IRunderground-Intrusive IR

2. Characteristics of 2. Characteristics of Igneous RocksIgneous Rocksa.a. TextureTexture- The size, shape - The size, shape

and arrangement of the and arrangement of the mineral crystals or mineral crystals or grains of rocks. grains of rocks.

• Slow cooling- Large Slow cooling- Large Crystals, intrusively Crystals, intrusively formedformed

• Rapid cooling- Small Rapid cooling- Small Crystals, extrusively Crystals, extrusively formedformed

b. Mineral Composition- b. Mineral Composition- Minerals that make up Minerals that make up the rock. Made of a the rock. Made of a combination of 8. combination of 8. (Muscovite and biotite (Muscovite and biotite mica, Quartz, Potassium mica, Quartz, Potassium and Plagioclase and Plagioclase Feldspar, Amphibole, Feldspar, Amphibole, Pyroxene and Olivine)Pyroxene and Olivine)

Pictures of 8 minerals Pictures of 8 minerals that comprise Igneous that comprise Igneous RocksRocks

Felsic

Mafic

3. Textures of Igneous 3. Textures of Igneous RocksRocksa. Intrusive a. Intrusive

(Plutonic)(Plutonic) Magma trapped Magma trapped underground underground and solidifies. and solidifies. As a result of As a result of slow cooling slow cooling large crystals large crystals are able to are able to form.form.

3a. Intrusive Igneous 3a. Intrusive Igneous RocksRocks1.1. Pegmatic Pegmatic (Very (Very

Coarse)-Coarse)- Crystals Crystals >10mm, very >10mm, very slow cooling. slow cooling. (Pegmatite)(Pegmatite)

2.2. Phaneritic Phaneritic (Coarse)(Coarse) Crystals Crystals 1-10mm, slow 1-10mm, slow cooling. Granite cooling. Granite and (Gabbro)and (Gabbro)

3. Textures of Igneous 3. Textures of Igneous RocksRocksb. Extrusive b. Extrusive

(Volcanic)(Volcanic) Formed from Formed from the rapid the rapid cooling of lava cooling of lava result the rock result the rock has a very fine has a very fine structure and structure and sometimes sometimes none at allnone at all

3b. Extrusive Igneous 3b. Extrusive Igneous RocksRocks1.1. Aphanitic Aphanitic (fine (fine

texture)texture) crystals crystals <1mm.(Rhyolite)<1mm.(Rhyolite)

2.2. Glassy-Glassy- Result of Result of rapid cooling no rapid cooling no visible crystals at visible crystals at all. (Obsidian)all. (Obsidian)

3.3. Vesicular-Vesicular- Rapid Rapid cooling of gas filled cooling of gas filled lava, has holes. lava, has holes. (Pumice)(Pumice)

4.4. Pyroclastic-Pyroclastic- Particles emitted Particles emitted from volcanoes. from volcanoes.

3c. Intrusive and 3c. Intrusive and Extrusive Extrusive 1. 1. Porphyritic-Porphyritic- Has Has

both small and both small and large crystals. large crystals. Result of cooling Result of cooling underground- underground- Large Crystals Large Crystals (Phenocrysts) and (Phenocrysts) and rapid cooling rapid cooling above ground above ground (Groundmass or (Groundmass or matrix)matrix)

4. Mineral Composition4. Mineral Composition

a.a. Felsic Group-Felsic Group- Igneous Igneous rock contains mostly rock contains mostly Quartz, Potassium Quartz, Potassium and Plagioclase and Plagioclase Feldspar, tend to be Feldspar, tend to be light colored and low light colored and low density.density.

b.b. Mafic Group-Mafic Group- Igneous Igneous rock contains mostly rock contains mostly Olivine, pyroxene, Olivine, pyroxene, and amphibole, tend and amphibole, tend to be dark colored to be dark colored and higher in density.and higher in density.

5. How to Identify 5. How to Identify Igneous RocksIgneous Rocks

1.1. Identify rocks color index Identify rocks color index • Light Colored- FelsicLight Colored- Felsic• Dark Colored- MaficDark Colored- Mafic

2.2. Identify mineral composition by Identify mineral composition by Color index.Color index.

3.3. Identify Rocks TextureIdentify Rocks Texture• Intrusive- large crystalsIntrusive- large crystals• Extrusive- Small or no crystals or Extrusive- Small or no crystals or

gas bubbles.gas bubbles.