Igneous Rocks

Inside Earth Chapter 5.2Pages 150-153

• Form from Lava or Magma• Made of mineral crystals• Classified according to:–Origin– Texture–Mineral Composition

Igneous Rocks

• Classified according to where they formed.

Intrusive Extrusive

Origin of Igneous Rocks

Intrusive

• Forms when magma hardens beneath Earth’s surface• Granite makes up

most of the continental crust.

Origin of Igneous Rocks

Extrusive

• Forms from lava that erupted onto Earth’s surface• Basalt forms much

of the ocean crust.

Origin of Igneous Rocks

A •Streak

B •Origin

C •Solid

D •HardnessWhich is a way to identify if a

rock is Igneous?

Igneous Rock Textures

•Slowly cooling, large crystals•Example: GraniteCoarse

Grained

•Lava cools quickly•Forms smaller crystals.Fine Grained

•Both textures – large AND small crystals.

•Cools slowly, then rapidly.

Porphyritic

•Rock cools too quickly for crystals to form.

No Crystals

• A solid in which the atoms are arranged in a pattern that repeats again and again.

What is a Crystal?

• Depends on the size and shape of it’s mineral crystals.

Igneous Rock Textures

Coarse Grained Porphyritic Fine Grained

No Crystals No Crystals

A •Coarse-grained

B •Fine-grained

C •Porphyritic

D •No visible crystalsA rock that has two kinds of

texture is called…

• Most of Earth’s rocks contain silica (silicon dioxide, SiO2)

Mineral Composition

High Silica (Felsic)

• Forms light colored rocks.• Granite is dark to light

gray, red and pink.

Low Silica (Mafic)

• Forms dark colored rocks.• Basalt contains dark

colored minerals. No quartz.

Silica Content

• Felsic– Granite– Rhyolite

• Mafic–Basalt–Gabbro

• Intermediate– Diorite– Andesite

Igneous Rock Chart

Origin

Intrusive

(Magma)

Coarse

Grained

GraniteContinental

CrustGabbro

Both Porphyritic

Large crystals with small crystals

Scattered on top.

Extrusive

(Lava)

Fine- Grain

edRhyolite

BasaltOcean

Crust

No Cryst

als Pumice Obsidian

Low Density HighFelsic (High) Silica Mafic (low)

A B C

Which rock likely has the most silica?

Granite - building materials

Obsidian - sharp tools

Basalt - gravel, construction

Pumice - used for cleaning and polishing

Uses of Igneous Rocks

• Igneous rocks are useful because they are hard, durable and dense

What to Work On

• Read the textbook, pages 150-153Answer questions 1-4 on page 153

DUE: Friday, November 4th

Project Topics• Plasma• Dark Matter• Hot air balloons• Light (double-slit experiment)• Elements (Uut, Uuq, Uuh)• History of Enlgish / metric units• TauTona