Warm Up 10/2Warm Up 10/2

On Front White BoardOn Front White Board

Igneous RocksIgneous Rocks

Chapter 3, Section 2Chapter 3, Section 2

Formation of Igneous RocksFormation of Igneous Rocks

Rocks that form when magma hardens Rocks that form when magma hardens beneath Earth’s surface are called beneath Earth’s surface are called intrusive igneous rocksintrusive igneous rocks

They have They have intrudedintruded into the existing into the existing rocksrocks

As magma rises it cools, allowing As magma rises it cools, allowing elements to combine and form elements to combine and form minerals, which combine to form minerals, which combine to form igneous rocksigneous rocks

When lava hardens, the rocks that form When lava hardens, the rocks that form are called extrusive igneous rocksare called extrusive igneous rocks

The have The have extrudedextruded onto the surface onto the surface

Evolution Evolution of a of a

MagmaMagma

Formation of Igneous RocksFormation of Igneous Rocks

Intrusive - Granite

Extrusive - Rhyolite

Classification of Igneous Classification of Igneous RocksRocks

Texture and composition are two Texture and composition are two characteristics used to classify characteristics used to classify igneous rocksigneous rocks

Texture describes the appearance of Texture describes the appearance of an igneous rock based on its size, an igneous rock based on its size, shape, and arrangement of shape, and arrangement of interlocking crystalsinterlocking crystals

Composition describes the proportions Composition describes the proportions of light and dark minerals in the rockof light and dark minerals in the rock

Course/Fine-Grained Course/Fine-Grained TextureTexture

If the magma cools slowly, it will have If the magma cools slowly, it will have only have a few centers of crystal only have a few centers of crystal growthgrowth

Slow cooling results in the formation of Slow cooling results in the formation of large crystals (course-grained)large crystals (course-grained)

If magma or lava cools rapidly, a large If magma or lava cools rapidly, a large number of tiny crystals compete for number of tiny crystals compete for available ionsavailable ions

Rapid cooling of magma or lava results Rapid cooling of magma or lava results in rocks with small, interconnected in rocks with small, interconnected mineral grains (fine-grained)mineral grains (fine-grained)

Course/Fine-Grained Course/Fine-Grained TextureTexture

Course-Grained Gabbro Fine-Grained Basalt

Glassy/Porphyritic TextureGlassy/Porphyritic Texture

Glassy Texture – solids produced so Glassy Texture – solids produced so quickly that the ions are not able to quickly that the ions are not able to alignalign

Porphyritic Texture – rocks that have Porphyritic Texture – rocks that have different size minerals, a result of different size minerals, a result of different rates of coolingdifferent rates of cooling

Glassy/Porphyritic TextureGlassy/Porphyritic Texture

Glassy Texture - Obsidian

Porphyritic Texture - Andesite

Concept CheckConcept Check How does the rate of cooling of magma How does the rate of cooling of magma

or lava affect the texture of igneous or lava affect the texture of igneous rocks?rocks?

A slowly cooling magma or lava will A slowly cooling magma or lava will produce rocks in which the mineral produce rocks in which the mineral grains are relatively large. Quickly grains are relatively large. Quickly cooling molten material will result in cooling molten material will result in rocks with small mineral grains. Lava rocks with small mineral grains. Lava that cools rapidly will produce a glassy that cools rapidly will produce a glassy rock. Rocks that form as a result of rock. Rocks that form as a result of different cooling rates will have both different cooling rates will have both large and small mineral grains.large and small mineral grains.

Granitic/Basaltic Granitic/Basaltic CompositionComposition

Granitic Composition – Igneous rocks Granitic Composition – Igneous rocks in which quartz and feldspar are the in which quartz and feldspar are the dominant mineralsdominant minerals

Most granitic rocks also contain Most granitic rocks also contain about 10% dark silicate minerals and about 10% dark silicate minerals and 70% light silicate minerals70% light silicate minerals

Basaltic Composition – rocks that Basaltic Composition – rocks that contain many dark silicate mineralscontain many dark silicate minerals

Basaltic rocks are rich in iron and Basaltic rocks are rich in iron and magnesiummagnesium

Granitic/Basaltic Granitic/Basaltic CompositionComposition

Granitic Composition - Granite

Basaltic Composition - Gabbro

Other Compositional GroupsOther Compositional Groups

Andesitic Composition – rocks with a Andesitic Composition – rocks with a composition between granitic and composition between granitic and basalticbasaltic

Andesitic rocks contain at least 25% Andesitic rocks contain at least 25% dark silicate mineralsdark silicate minerals

Ultramafic – rocks that are composed Ultramafic – rocks that are composed mostly of dark silicate mineralsmostly of dark silicate minerals

Peridotite is an example of an Peridotite is an example of an ultramafic rock, although rare on the ultramafic rock, although rare on the crust, it is thought that the mantle is crust, it is thought that the mantle is made mostly of peridotitemade mostly of peridotite

Other Compositional GroupsOther Compositional GroupsAndesitic Composition - Andesite

Ultramafic - Peridotite

Bowen’s Reaction SeriesBowen’s Reaction Series

Classification of Igneous Classification of Igneous RocksRocks

Concept CheckConcept Check

Describe the main differences Describe the main differences between granitic and basaltic rocks?between granitic and basaltic rocks?

Granitic rocks contain mostly quartz Granitic rocks contain mostly quartz and feldspar and thus are light-and feldspar and thus are light-colored. Basaltic rocks are rich in colored. Basaltic rocks are rich in iron and thus are dark-colored and iron and thus are dark-colored and more dense.more dense.

HomeworkHomework

Read Chapter 3, Section 2 (pg. 70-Read Chapter 3, Section 2 (pg. 70-74)74)

Do 3.2 Assessment #1-7 (pg. 74)Do 3.2 Assessment #1-7 (pg. 74) Print out “Investigation 3 – Print out “Investigation 3 –

Classifying Rocks Using a Key” for Classifying Rocks Using a Key” for next classnext class

AssignmentAssignment

Create a Rock Cycle Poster!Create a Rock Cycle Poster! Your poster should have: Your poster should have:

a.a. Captions (5 points)Captions (5 points)

b.b. Color (5 points)Color (5 points)

c.c. Drawings of each step (5 points)Drawings of each step (5 points)

d.d. Be neat (5 points)Be neat (5 points)

You may use page 67 of the text to guide You may use page 67 of the text to guide you.you.