1. Rocks

2. Rocks
Naturally occurring solid mixtures of one or more minerals and organic matter
They can be made of two or more different minerals that have been:
cemented together
squeezed and heated together
melted and cooled together

3. Types of Rocks
Igneous
Sedimentary
Metamorphic

4. Igneous rocks are classified in three ways:
Most igneous rocks are produced deep underground by the cooling and hardening of magma.
Igneous rocks are classified in three ways:
Origin – where they are formed
Composition – refers to the minerals that make up the rock
Texture – the shape, size, arrangement and distribution of minerals that make up the rock

5. Origin Intrusive - Formed deep within the earth
Granite
Extrusive- Formed from lava; volcanic
Pumice
Obsidian

6. Intrusive Igneous Rocks
Intrusive igneous rocks are formed deep within the Earth
Granite is the most common (continental crust)
Quartz
Mica
Hornblende
Feldspar
Intrusive masses named for their size and shape

7. Plutons are large irregularly shaped intrusions
Batholiths – largest
intrusive bodies
Stocks – smaller areas
than batholiths
Sills – sheet-like
intrusions parallel to
previous layers
Dikes - sheet-like
intrusions that cut across previous rock layers at an angle

10. Intrusive Igneous Rocks
Pegmatite
Granite
Diorite
Gabbro

11. Extrusive Igneous Rocks
Formed from lava; volcanic
Basalt is the most common (oceanic crust)
Cools quickly and contains very small, or no crystals
Can erupt from fissures, which are long cracks in the Earth

12. Extrusive Igneous Rocks
Obsidian
Pumice
Rhyolite
Andesite
Basalt
Scoria

13. Composition Refers to the minerals that make up the rock Felsic
light-colored rocks
less dense
contain elements such as aluminum, potassium, silicon, & sodium
Mafic
dark-colored rocks
denser
rich in calcium, iron and magnesium (poor in silicon)

14. The size of the crystals depends on:
Texture – refers to the shape, size, arrangement and distribution of the minerals that make up the rock
Fine-grained
Coarse-grained
Glassy
Porphyritic
The size of the crystals depends on:
Rapid cooling = fine-grained with small crystals
Slow cooling = coarse-grained with large crystals

15. Textures Glassy Coarse-grained Granite Obsidian Fine-grained
Porphyritic
Basalt
Granite

16. Composition and Texture of Igneous Rock