1. Rocks
3.1 The Rock Cycle
 Rocks – naturally occurring, solid mass of minerals
 Types of Rocks
1. Igneous rock - formed by the crystallization of molten magma/lava.

2. 3.1 The Rock Cycle Rocks  Types of Rocks
2. Sedimentary rock - formed from weathered products of preexisting rocks that have been transported, deposited, compacted, and cemented.
3. Metamorphic rock - formed by the alteration of preexisting rock deep within Earth (still in the solid state) by heat, pressure, and/or chemically active fluids.

3. 3.1 The Rock Cycle The Rock Cycle
 Interrelationships among the three rock types (igneous, sedimentary, and metamorphic)
 Magma - molten material deep beneath the Earth’s surface.
 Lava - magma that reaches the surface.
 Weathering - process in which rocks are broken down by water, air, and living things.
 Sediment - weathered pieces of Earth elements.

4. The Rock Cycle

5. 3.1 The Rock Cycle Energy That Drives the Rock Cycle
 Heat from the Earth’s interior forms igneous rock and metamorphic rock.
 Weathering and erosion are external processes powered by the sun that form sedimentary rocks.

6. 3.2 Igneous Rocks Formation of Igneous Rocks
1. Intrusive igneous rocks - formed when magma hardens beneath Earth’s surface.
2. Extrusive igneous rocks - formed when lava hardens at Earth’s surface.

7. 3.2 Igneous Rocks Classification of Igneous Rocks
 Igneous rocks are classified by composition and texture.
1. Texture
• Coarse-grained texture (large crystals) is caused by slow cooling.
• Fine-grained texture (small grains) is caused by rapid cooling.

8. 3.2 Igneous Rocks Classification of Igneous Rocks
1. Texture (continued)
• Glassy texture is caused by very rapid cooling.
• Porphyritic texture is caused by different rates of cooling resulting in varied mineral sizes.
2. Composition
• Granitic composition rocks are made mostly of light-colored quartz and feldspar.

9. 3.2 Igneous Rocks Classification of Igneous Rocks
2. Composition (continued)
• Basaltic composition rocks are made mostly of dark-colored silicate minerals and plagioclase feldspar.
• Andesitic composition rocks are between granitic, light-color minerals and basaltic, dark-colored minerals.
• Ultramafic composition rocks are made mostly from iron and magnesium-rich minerals.

10. Classification of Igneous Rocks

11. 3.3 Sedimentary Rocks Formation of Sedimentary Rocks
• Weathering – breakdown of rock
Erosion – transport of broken sediments
• Deposition - when an agent of erosion—water, wind, ice, or gravity—drops sediments.

12. 3.3 Sedimentary Rocks Formation of Sedimentary Rocks
• Compaction - process that squeezes/compacts sediments.
• Cementation - when dissolved minerals are deposited in the tiny spaces of sediments.
 Features of sedimentary rocks are clues to how and where the rocks are formed

13. 3.3 Sedimentary Rocks Classification of Sedimentary Rocks
1. Clastic sedimentary rocks - composed of weathered bits of rocks and minerals.
• Classified by particle size
• Common examples:
- Shale (most abundant)
- Sandstone
- Conglomerate

14. 3.3 Sedimentary Rocks Classification of Sedimentary Rocks
2. Chemical sedimentary rocks form when dissolved substances precipitate, or separate, from water.
Common rocks include
- limestone—most abundant chemical rock
- microcrystalline quartz known as chert, flint, jasper, or agate
- evaporites such as rock salt or gypsum
- coal

15. Classification of Sedimentary Rocks

16. 3.4 Metamorphic Rocks Formation of Metamorphic Rocks
 Metamorphism means “to change form.”
 Formation occurs at high temperatures and pressures.
 Conditions are found a few km below the Earth’s surface and extend into the upper mantle.

17. 3.4 Metamorphic Rocks Formation of Metamorphic Rocks
 Contact metamorphism occurs when magma moves into rock.
Occurs near a body of magma
Changes are driven by a rise in temperature.

18. 3.4 Metamorphic Rocks Formation of Metamorphic Rocks
 Regional metamorphism results in large-scale deformation and high-grade metamorphism.
Directed pressures and high temperatures occur during mountain building.
Produces the greatest volume of metamorphic rock

19. 3.4 Metamorphic Rocks Agents of Metamorphism  Heat  Pressure
Provides the energy needed to drive chemical reactions
 Pressure
Causes a more compact rock with greater density

20. 3.4 Metamorphic Rocks Agents of Metamorphism  Hydrothermal Solutions
Hot water-based solutions escaping from the mass of magma
Promote recrystallization by dissolving original minerals and then depositing new ones

21. 3.4 Metamorphic Rocks Classification of Metamorphic Rocks
 Two main categories
1. Foliated Metamorphic Rock
Has a banded or layered appearance
2. Nonfoliated Metamorphic Rock
Does not have a banded texture

22. Classification of Metamorphic Rocks