CHAPTER 6, SECTION 2

Standards 3c. Students know how to explain the properties of rocks based on the physical and chemical conditions in which they are formed, including plate tectonic properties.

Objective 1 Summarize 3 factors that affect whether rock melts.

Objective 2 Describe how the cooling rate of magma and lava affects the texture of igneous rocks.

Objective 3 Classify igneous rocks according to their composition and texture.

Objective 4 Describe intrusive and extrusive igneous rock structures.

Assessment End of Section Questions, Daily Quiz, Chapter Test

Review Daily Bellwork, Science Starters, Standards Practice

KEY TERMS

Create a flash card for the following key terms (p. 129 in textbook):

Igneous RockIntrusive Igneous RockExtrusive Igneous RockFelsicMafic

If you finish early, study your flash cards!

IGNEOUS ROCK

Most Igneous Rock (formed from cooled magma) is crystalline (made of crystals).

Magma forms when rocks melt.

3 Factors determine when rock melts: temperature, pressure, and pressure of fluids in the rock.

IGNEOUS ROCK VIDEO CLIP

PARTIAL MELTING Different minerals have different melting

points. Minerals with lower melting points, melt first. The process of different minerals in the rock

melting at different temperatures is called PARTIAL MELTING.

FRACTIONAL CRYSTALLIZATION

When magma cools, the opposite of partial melting occurs: freezing.

Different minerals have different freezing points.

As some minerals freeze, the composition of the remaining magma changes, creating new minerals.

This is called fractional crystallization.

FRACTIONAL CRYSTALLIZATION

Crystals that freeze/form early tend to be the largest.

TYPES OF IGNEOUS ROCK

• Magma that cools deep inside the crust

Intrusive

• Lava that cools at the Earth’s surface

Extrusive

INTERACTIVE!

Create and Acrostic Poem using the word IGNEOUS.

I G N E O U S

TEXTURES OF IGNEOUS ROCKS

Coarse-Grained

• Intrusive• Large, well-

developed mineral crystals

• Ex.: Granite

Fine-Grained

• Extrusive• Small Mineral

Grains• Grains cannot be

seen with human eye

• Ex: Basalt

Other

• Mixture of large and small crystals

• Forms as a result of slow cooling at first then rapid cooling.

• Highly viscous magma that cools quickly results in very few crystals• If this magma has

little gas=GLASSY• If this magma has

lots of gases=VESICULAR (holes)

TEXTURES VIDEO CLIP

QUICK CHECK!!1. Name the 2 types of Igneous Rock:

____________________________________________2. Give an example of a Course-Grained Igneous

Rock: ______________________________________

COMPOSITION OF IGNEOUS ROCKSMineral Composition of igneous

rocks is determined by the chemical composition of the magma from which the rock formed.

Three families of igneous rock:FelsicMaficIntermediate

COMPOSITION FAMILIESFels

ic R

ock • Forms

from Magma that has large amount of Silica.

• Light coloring

• Contains feldspar

Mafi

c R

ock • Forms from Magma that has low amounts of silica and lots of iron and magnesium

• Dark in color

Inte

rmed

iate

R

ock• Contains

less silica than Felsic but more than Mafic

INTRUSIVE ROCK STRUCTURES Igneous Rock masses that form underground are called

INTRUSIONS. 5 types of intrusions:

Batholiths—largest of all intrusions, larger than 100 km squared, form the core of mountains

Stocks—same as a batholith but smaller than 100 square km.

Laccoliths— “lake of rock”, when magma flows between rock layers and spreads upward into a dome shape.

Sills-when magma flows between the layers of rock and hardens. Always parallel to the layers of rock below and above.

Dike-Magma that forces itself through vertical fractures and solidifies.

EXTRUSIVE ROCK STRUCTURESIgneous rock masses that form on Earth’s surface are called EXTRUSIVE ROCK STRUCTURES.

Lava from a volcano that cools and becomes rock is an EXTRUSIVE ROCK STRUCTURE.

ANIMATED INTRUSIVE AND EXTRUSIVE FEATURES

QUICK CHECK!!1. What is the difference between Intrusive and

Extrusive Rock Structures? __________________________________________________________________________________________________________________________________________

2. What is Felsic Rock? ____________________________________________________________________________________________

3. Name and Define 2 types of Intrusive Rock Structures: ________________________________________________________________________________________________________________________________________________________________________________________

ASSESSMENT In groups create posters for one of the

following: Intrusive Extrusive Course-Grained Fine-Grained Felsic Mafic Intermediate

DAILY QUIZ