Objective:  

1. Understand the processes that produce igneous rocks.
2. Understand the geometry and origin of intrusive and extrusive bodies of igneous rocks.
3. Be able to describe, name, and interpret textural features of igneous rocks.
4. Be able to describe the composition and mineralogy of igneous rocks.
5. Be able to classify common igneous rocks based on their texture and composition.
6. Infer the origin of common igneous rocks.

Equipment:  

• writing utensil

• metric ruler, marked in millimeters, preferably clear.

• magnifier

• igneous rock classification charts  (in your lab manual, fig. 5.2 (p. 78), Fig. 5.3 (p. 79) and supplemental handouts at right)

• identification sheet (provided)

• mineral identification kit (provided)

• igneous rock samples (provided)

• chart for estimation of percent (cardboard model 1, near back of book, for example)

• Stereographic lenses (provided)

• Additional Identification guides (optional)

Activities:  

Before Class

1. Read Laboratory 5: Igneous Rocks and Volcanic Hazards (p. 76-93)

2. Study the following figures:

   1. Fig. 5.1, p. 77

   2. Fig. 5.2, p. 78

   3. Fig. 5.3, p. 79

   4. Fig. 5.4-5.16, p. 82-87

3. Write down any questions you would like to ask or topics that need clarified.

4. Complete and submit the Pre-Lab Exercise

5. Look over the Key Terms below.  Familiarize yourself with the terms and ideas listed.

During Class

1. We will have our first exam.

2. I will answer any questions regarding this week's readings in Laboratory 5: Igneous Rocks.

3. I will return (if you haven't already picked them up) and field questions regarding Exercises for labs on Mineral Properties and Mineral Identification, creation of Magma and Pre-Lab Exercise 5: Igneous Rocks.

4. Lecture over Igneous rocks.

5. We will work on Lab Exercise 5: Identification of Igneous Rocks, essentially question  8, p. 90. (19 SEP 04 this is not quite ready yet!)

After Class

1. Finish ID of Igneous Rocks

2. Work on Post-Lab 5: Igneous Bodies

3. Proceed to next lesson

Key Terms and Ideas

1. igneous processes and rocks

2. magma

3. magma chamber

4. lava

5. intrusion

6. batholith

7. pluton

8. sill

9. dike

10. intrusive igneous rocks

11. extrusive igneous rocks

12. volcano

13. pyroclastic deposits and texture

14. volcanic ash

15. lapilli or cinder

16. volcanic blocks

17. lava flow

18. textures (know how to recognize, define, and explain the origin of the following):

    • glassy

    • aphanitic

    • phaneritic

    • pegmatitic

    • porphyritic

    • vesicular

19. other textural terms

    • phenocryst

    • groundmass

20. color index

21. mafic minerals and composition and rocks

22. felsic minerals and composition and rocks

23. intermediate composition and rocks

24. ultra-mafic composition and rocks

25. know how to identify, the formula of,  and the physical properties of the common igneous rock-forming minerals:

    • quartz

    • K-feldspar

    • plagioclase-feldspar

    • olivine

    • pyroxene

    • amphibole

    • biotite

    • muscovite

26. know the names of common igneous rocks:

    • syenite (porphyry, pegmatite)

    • granite (porphyry, pegmatite)

    • diorite (porphyry, pegmatite)

    • gabbro (porphyry, pegmatite)

    • peridotite

    • rhyolite (porphyry)

    • andesite (porphyry)

    • basalt (porphyry)

    • obsidian

    • pumice

    • scoria

    • volcanic tuff

    • volcanic breccia

27. Bowen's reaction series

28. fractional crystallization

29. partial melting

30. asthenosphere

31. lithosphere

32. crust

33. mantle

Questions to Think About

1. What are igneous rocks?
2. What observable characteristics define igneous rocks?
3. List the various (~6?) textures of igneous rocks and describe what each can tell us about the cooling history of the rock.
4. Igneous rock textures are controlled by what factors?
5. What is the distinction between magma and lava?
6. How is texture indicative of the genesis or formation of igneous rocks?
7. What do the rock names obsidian, pumice, scoria, tuff, and breccia imply with regards to the texture and mode of formation of the rock?
8. What are extrusive rocks and how are they classified?
9. How do water vapor and other gases effect the texture of extrusive igneous rocks?
10. How would you distinguish between basalt, andesite, and rhyolite if no phenocrysts are present?
11. What minerals are likely to form phenocrysts in a basalt and why?
12. Is K-feldspar present in all granites?
13. Is quartz common in the gabbro-basalt family of rocks? Explain.
14. What does the terms "felsic" and "mafic"  mean?  How were they derived?
15. Explain haw a vesicular porphyritic andesite may have formed?
16. Why don't basalts build volcanic cones?
17. Draw, label and understand the significance of Bowen's Reaction Series.
18. In terms of Bowen's reaction series, how would you interpret olivine crystals that have an outer rim or coating of augite?
19. How can Bowen's reaction series be used to predict mineral associations in igneous rocks?
20. How can Bowen's reaction series be used to explain textural relationships of individual mineral crystals within an igneous rock?
21. How does the chemical composition of a magma impose limitations on the type of minerals that will form in the resulting rock

Additional Resources

IUGS Classification of Igneous Rocks --

BOOKS -- 

WEB SITES -- see the Link List