1. Igneous Rocks

2. Igneous Rocks Form from the crystallization of magma
From Latin “ignis” which means fire
Most common rocks in the Earths crust by far
Two types of Igneous Rock

3. Extrusive Cools quickly on the Earth’s surface Fine-grained Evidence
We can actually watch extrusive igneous rocks from as lava cools

4. Intrusive Cools slowly beneath the surface of the Earth
Coarse-grained (large/rough)
Evidence
Cross-cutting relationship with other rock formations

5. Cross-cutting Most igneous intrusive rocks have cross-cut something
Magma comes up through cracks in rocks
Magma the cools leaving an igneous intrusion
Granite is the most common intrusive igneous rock

6. Magma Not a pure substance Usually contains
Molten rock
Gases
Mineral crystals
Contains the same elements found in the Earth’s crust
Most abundant compound is Silica (SiO4)
Found in almost all rocks

7. Melting Not all parts of magma melt at the same time
This concept is called partial melting

8. Crystallization
Not all parts of magma crystallize (harden) at the same time
This concept is called fractional crystallization
Harder substances (diamonds) harden at the same time and are harder to melt
Pressure causes substances to have different melting points

9. Bowen’s Reaction Series
Shows the relationship between cooling magma and mineral formation

10. Mineral composition Again silica is the primary component of magma
Felsic rocks contain high levels of silica
Resistant to flow
Granite, Obsidian
Mafic rocks contain low levels of silica
“watery stew”
Gabbro, Basalt

11. Uses Interlocking grain textures make them very strong
They are also highly resistant to weathering
These characteristics make Igneous rocks excellent building materials.

12. Sedimentary rocks

13. Sedimentary Rocks
Composed of small pieces of rocks that have been broken down and deposited
Wind, water, and other forces transport sediments to sedimentary basins which can be more than 8 km thick.

14. Clastic sediments Boulder > 256 mm Cobble 256 - 64 mm
Pebble mm
Sand 2 – mm
Silt – mm
Clay < mm

15. Buried Sediments experience high pressure and temperature
This causes lithification, which is the process of sediments turning into rock
Sedimentary rocks can also form from cementation
Sediments are cemented together by mineral growth

16. Sedimentary Uses Evidence of past events and life Energy sources
Due to the presence of fossils
Energy sources
Oil
Natural gas
Coal

17. Metamorphic rocks

18. Metamorphic Rocks
From the Greek “meta” meaning change, and “morphe” meaning form
Rock is buried and experiences great pressure and temperature, but doesn’t quite melt
Very common in “mountain-building” areas
During metamorphism, rocks change form while remaining solid

19. Types of metamorphic rock
Foliated
Minerals with flat needle-like structures line up in wavy layers and bands
Non-foliated
Mineral grains lack the flattened structure

20. Rock Cycle
The remaking of rocks