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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
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
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