Ch. 5 Sec. 2 Igneous Rocks

igneous rockigneous rock – – formed from magma or lavaformed from magma or lava

classified by

1. origin 2. texture3. mineral

composition

where formed?

on or beneathEarth’s surface

depends on size & shape

of mineral crystals

Silica content

1. origin

• extrusive rock= formed from lava on Earth’s surface

–ex. basalt

• intrusive rock= formed from magma below Earth’s surface

–ex. granite

2. texture• depends on size & shape of mineral crystals

different textures

1. fine-grained • small crystals• rapid cooling

2. coarse-grained • large crystals • slow cooling

3. porphyritic • large crystals surrounded by smaller crystals• forms when magma cools slowly- then rapidly

4. glassy • no crystals form • extremely rapid cooling

coarse-grained fine-grained

porphyritic

3. mineral composition

• lava low in silica dark colored rocks

• lava high in silicalava high in silica light colored rocks light colored rocks

uses of igneous rocks

• hard, dense, & durable

• ex:

• granite• building material

statuesfloors

• pumice• good abrasive for cleaning & polishing

basalt• makes gravel in construction

What does igneous rock form from?

magma or lavamagma or lava

How are igneous rocks classified?

• according to:

1.origin

2.texture

3.mineral composition

Why have people throughout history used igneous rocks for tools and building materials?

• They are hard, dense, & durable.

What igneous rock is used to make gravel in construction?

basalt

What type of igneous rock formed from lava on Earth’s surface ?

extrusive rock

What type of igneous rock formed from magma below Earth’s surface ?

intrusive rock