1. Igneous Rock Classification
Dr. David Steer

2. Rock cycle

3. Analysis Time
Given:
Bag rocks
Group these rocks in some manner

4. Grouping items Group these objects in some logical way.
Color (Proxy for silica content)
Size (Proxy for grain size)
Group these objects in some logical way.

5. Grouping items
Group these objects in some logical way.

6. Analysis time
Given:
Bag rocks
Group these rocks in some manner

7. Rock Cycle

8. Igneous Rocks Volcanic (extrusive) igneous rocks
Cool fast, small crystals
form when molten rock (magma) in the earth’s interior rises to the surface through pipes or fractures in the crust.

9. Igneous Rocks Plutonic (intrusive) igneous rocks
Cool slow, large crystals
form when magma cools within the earth. Igneous rocks that cool below the earth's surface are termed plutonic (or intrusive) igneous rocks.

10. Classification of Igneous rocks
Texture size of crystals most important
Cooling rates
Surface, fast
Small crystals
Below surface slow
Larger crystals
Which formed at surface?
Both are the same chemistry a) b)
Rhyolite
Granite

11. Chemical Composition Color
Indicative of chemistry and temperatures of formation
Dark colors
High temperatures (1000 to 1200 oC)
Low silica content
Light colors
Lower temperatures
High silica content
Which is the high silica rock?
Both formed below the surface a) b)
Gabbro
Granite

12. Texture
So explain this!!!!

13. Six common Igneous Rocks
Solidifying Temperature
500 C
Increasing Grain Size
Volcanic Rocks
Silica Content
Minerals Present (in order of abundance)
Plutonic Rocks
Basalt
low
pyroxene, olivine, feldspar, & amphibole
Gabbro
Andesite
intermediate
feldspar, amphibole, pyroxene, biotite mica
Diorite
Rhyolite
high
feldspar, quartz, muscovite mica, & amphibole
Granite
Lighter Color

14. Basalt Color Cool Quick Cool Slow Dark Extrusive
Draw a concept map that guides you through classifying an igneous rock.
Use these terms to: Classify Igneous Rocks
Basalt Color Cool Quick
Cool Slow Dark Extrusive
Gabbro Granite High Silica
Large Grain Low Silica Light
Plutonic Texture Rhyolite
Small Grain

15. Identify the rock type associated with the diagram below.
Question
Plot 1
Plot 2
Plot 3
Plot 4
andesite porphory
gabbro
basalt
obsidian

16. 5) Imagine that all minerals found in rocks were the same color
5) Imagine that all minerals found in rocks were the same color. What information would you no longer be able to infer? a. texture b. cooling rate c. composition

17. Analysis Time
Given:
Bag rocks
Identify the rocks