1. Igneous Rocks The root word ignis comes with the latin word for “fire”
Igneous rocks form from crystallization of magma (below Earth’s surface) or lava (above Earth’s surface)

2. Igneous Rocks
Magma is a slushy mix of molten rock, gases, and mineral crystals
The main compound in magma is silica (SiO2)
Controls melting point and viscosity how well lava flows

3. Igneous Rocks
It takes temperatures of °C deep within the Earth to melt rocks
The main factors involved in magma formation are:
Temperature
Pressure
Mineral Content
Water Content

4. Igneous Rocks As depth beneath the Earth increases, pressure increases
Melting point increases because particles are more densely packed

5. Igneous Rocks
Different substances = Different melting points = Partial Melting
As each group of minerals melts, different elements are added to magma, changing its composition

6. Igneous Rocks
During cooling, the last minerals to melt are the first to crystallize. This called fractional crystallization.
Why?

7. Types of Igneous Rocks
Formation
Factors
Composition
What it looks like
Extrusive
Cools quickly from lava on Earth’s surface
Exposure to air and moisture
Calcium core surrounded by crystals
Glassy, fine-grained, hard to see crystals
Intrusive
Cools slowly from magma below Earth’s surface
Gradual temperature change; no environmental impact
High silica content, salt-rich
Rough texture, coarse-grained, big crystals

9. Igneous Resources
Minerals that contain useful substances that can be mined for profit are called ores.
Due to fractional crystallization, igneous ore deposits are often found in veins. We mine valuable substances such as gold, silver, lead, and copper.
Pegamites: large veins
Kimberlites: small veins (diamonds)

10. What do we use igneous rocks for?

11. Igneous Rock Summary Questions
1. Compare and contrast the process of baking cookies to the formation of igneous rocks:
How is the dough both similar to and different from magma?
Describe the viscosity of the dough that we made in class.
How does magma change when it is exposed to temperature change. How is this similar to and different from how the cookie dough changes when exposed to temperature change?
2. What type of igneous rock are you eating? Describe the texture, hardness, grain size, composition, etc and why it represents that type of igneous rock.
3. Sometimes similar minerals clump together in a rock sample. Do you see this happen in your cookie? Provide a hypothesis for why this might happen.

12. Sedimentary Rocks

13. Why did this happen?

14. Weathering= rocks and sediments break down
How do rocks on the Earth’s surface change?
Weathering= rocks and sediments break down
Erosion= smaller pieces are moved to new locations
Three types:
Physical (mechanical)
Chemical
Biological

15. What is physical weathering?
NO changes in composition
Size and shape change
Factors:
Temperature
Frost wedging: water freezes and expands, cracking rocks
Pressure
Exfoliation: pressure of overlying rocks are removed, underlying rocks can expand

16. Physical Weathering
Temperature
Pressure

17. Mineral composition CHANGES Chemical reaction occurs NEW minerals form
What is chemical weathering?
Mineral composition CHANGES
Chemical reaction occurs
NEW minerals form
Agents:
Water Hydrolysis
Oxygen Oxidation
Carbon Dioxide ex: cave
Acid ex: acid rain

18. Living organism cause changes in rocks or sediment
What is biological weathering?
Living organism cause changes in rocks or sediment
Ex: tree roots growing around a rock and splitting it
Ex: humans displacing or removing rock surfaces

19. What affects the rate of weathering?
CLIMATE
Chemical weathering is more common/faster in areas of warm temperatures and high rainfall
Ex: “Painted Desert” of Arizona/New Mexico
Physical weathering is more common/faster in areas of cool, dry climate
Ex: NC mountains

20. What are sediments?
Even though igneous rocks are the most common in Earth’s crust, most of Earth’s surface is covered in sediment.
Sediments: pieces of solid rock material re-deposited on Earth’s surface by forces (wind, water, ice, gravity, precipitation, etc.)

21. Weathered particles get moved downhill (erosion)
How do sediments become sedimentary rocks?
(Part 1)
Weathered particles get moved downhill (erosion)
Get laid down/sink (deposition)
Deposits become layered (sorting)
Layers stack up on top of each other (burial)
These processes add material to sedimentary basins

22. As burial occurs, layers are subjected to greater heat and pressure
How do sediments become sedimentary rocks?
(Part 2)
As burial occurs, layers are subjected to greater heat and pressure
These conditions cause lithification
lithos = stone
Sediments  Sedimentary Rocks
Two steps:
Compaction
Cementation

23. What is a sedimentary basin?
Newest, smallest particles
3rd oldest layer
2nd oldest layer
Oldest, largest particles
Depression in Earth’s crust

24. Bedding! Horizontal layers Graded bedding Bigger on the bottom
What do sedimentary rocks look like?
Bedding!
Horizontal layers
Graded bedding
Bigger on the bottom
Cross-bedding
Slanted layers

25. By formation Organic sedimentary rocks (from once living things)
How are sedimentary rocks classified?
By formation
Organic sedimentary rocks (from once living things)
Chemical sedimentary rocks (evaporites)
Clastic sedimentary rocks (loose deposits on Earth’s surface)—Most common

26. Metamorphic Rocks Change Form You tell me…what factors cause
chemical and
physical changes in
rocks??

27. Molten rock comes in contact with solid rock
What is contact metamorphism?
What is hydrothermal metamorphism?
Molten rock comes in contact with solid rock
High temperature/low pressure
Hot water comes in contact (reacts with) rock
High temperature/moderate pressure
Deep sea vents/volcanoes

28. How are metamorphic rocks classified?
Foliated
Non-Foliated

29. How are metamorphic rocks classified?
Foliated
Non-Foliated

30. What are porphyroblasts?
New metamorphic minerals grow LARGE while surrounding minerals remain small