1. Rocks

2. What are Rocks? How are they similar?
How are these rocks different from one another?
How are they similar?

3. What are Rocks?
A rock is a naturally occurring solid mixture of one or more minerals, or organic matter.
Rocks are classified by how they are formed, their composition, and texture.

4. What are Rocks? IGNEOUS SEDIMENTARY METAMORPHIC
Types of rocks according to ORIGIN:
IGNEOUS
SEDIMENTARY
METAMORPHIC

5. Igneous Rocks Igneous rock begins as magma. Magma is a mixture of
many minerals
magma
volcano

6. Igneous Rocks 1. Texture Classification of Igneous Rocks
• Coarse-grained texture is caused by slow cooling resulting in larger crystals.
• Fine-grained texture is caused by rapid cooling resulting in smaller, interconnected mineral grains.

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

8. 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 composition dark-colored minerals.
• Ultramafic composition rocks are made mostly from iron and magnesium-rich minerals.

9. Igneous Rocks

10. Igneous Rocks Coarse-Grained Fine-Grained Felsic Granite Rhyolite
Mafic
Basalt
Gabbro

11. Igneous Rocks
Intrusive Igneous Rocks: when magma pushes into surrounding rock below the Earth’s surface
Extrusive Igneous Rocks: when magma erupts onto the Earth’s surface (lava), cools quickly with very small or no crystals formed

12. Mafic, fine grained, extrusive
Obsidian
What is Obsidian?
Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form.
Igneous Rocks
Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form.
Is this rock Felsic or Mafic?
Is it fine-grained or coarse-grained?
Is this rock Intrusive or Extrusive?
Mafic, fine grained, extrusive

13. Sedimentary Rocks Sedimentary rock is formed by erosion.
Sediments are deposited in layers, with the older ones on the bottom.
sea
Fragments washed to the sea
Sedimentary
rocks
Rocks are broken
up by the action
of weather

14. Sedimentary Rocks The layers become compacted and cemented together.
Getting older
Stratification is the process in which sedimentary rocks are arranged in layers

15. Sedimentary Rocks

16. Sedimentary Rocks Classification of Sedimentary Rocks
1. Clastic/detrital sedimentary rocks are made of fragments of rock cemented together with calcite or quartz.
Breccia is a term most often used for clastic sedimentary rocks that are composed of large angular fragments (over two millimeters in diameter).

17. Sedimentary Rocks
2. Minerals crystallize out of solution to become chemical sedimentary rocks.
Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO3) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters.

18. Sedimentary Rocks
3. Organic sedimentary rocks are formed from the remains of plants and animals.
Coal is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment. 

19. Sedimentary Rocks
Classification of Sedimentary Rocks

20. Metamorphic Rocks heat Meaning to change shape
Changes with temperature and pressure, but remains solid
Usually takes place deep in the Earth
Magma
Pressure from surface rocks
metamorphic
rock
forms
here
heat

21. Metamorphic Rocks Metamorphic rocks form by:
1. Contact Metamorphism ~ heating by nearby magma
Hornfels is a fine-grained non-foliated metamorphic rock produced by contact metamorphism
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22. Metamorphic Rocks
2. Regional Metamorphism ~ pressure builds up in rocks that is deep within the Earth Large pieces of the Earth’s crust collide and the rock is deformed and chemically changed by heat and pressure.

23. 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

24. Metamorphic Rocks

25. Metamorphic Rocks Foliated ~contain aligned grains of flat minerals
Gneiss is foliated metamorphic rock that has a banded appearance and is made up of granular mineral grains.

26. Metamorphic Rocks
Non-Foliated ~mineral grains are not arranged in plains or bands
Marble is a non-foliated metamorphic rock that is produced from the metamorphism of limestone.

27. Metamorphic Rocks
Determine if the following rock samples are foliated or non-foliated: NF NF F
Amphibolite
Quartzite
Phyllite

28. The Rock Cycle
Does marble remain as marble forever? Can limestone (sedimentary) become marble (metamorphic)?

29. The Rock Cycle