1 of 53

Teaching Point: “To analyze igneous rocks texture and composition.”

Do now Discussion: How would you compare lava to other substances that you know?

2 of 53

Types of Rocks:

Igneous are cooled liquid rock into mineral crystals
Sedimentary are mostly glued sediment particles or chemical/biological in origin
Metamorphic are warped and “cooked” rocks made by heat and pressure

Let’s Review Rock Types

TP: “To analyze igneous rocks texture and composition.”

3 of 53

Task- Question: Describe the different positions of A and B. Can you also describe what might be happening at both A and B?

Igneous Rocks in Two Places

TP: “To analyze igneous rocks texture and composition.”

Surface

4 of 53

Extrusive rocks = lava cools __________ at the surface

Intrusive rocks = magma cools ________ deep in Earth

Two Igneous “Environments”

TP: “To analyze igneous rocks texture and composition.”

5 of 53

Task- Question: How do you think magma and lava cool differently given where they are located in the diagram?

Igneous Rocks and Cooling

TP: “To analyze igneous rocks texture and composition.”

Surface

6 of 53

Extrusive rocks = lava cools quickly at the surface

Intrusive rocks = magma cools slowly deep in Earth

Types of Igneous Rocks

TP: “To analyze igneous rocks texture and composition.”

7 of 53

Extrusive rocks = volcanic rocks

Intrusive rocks = plutonic rocks

Volcanic and Plutonic Rocks

TP: “To analyze igneous rocks texture and composition.”

8 of 53

Extrusive

Intrusive

Scheme for Igneous Rocks

TP: “To analyze igneous rocks texture and composition.”

9 of 53

Task- Question: How do you think the different cooling rates of extrusive and intrusive rocks affects the size of the minerals in that rock?

Crystal Size and Igneous Texture

Large Minerals

Small Minerals

TP: “To analyze igneous rocks texture and composition.”

10 of 53

Glassy = instant cooling; no mineral crystals

Fine = mineral crystals < 1mm, Individual grains cannot be seen without magnification

Vesicular = gas pockets; rocks cool and release gases

Extrusive Textures

TP: “To analyze igneous rocks texture and composition.”

Vesicular =

Gas Pockets

Glassy = Extreme rapid cooling

Fine grained

11 of 53

Extrusive Igneous Textures

Extrusive

TP: “To analyze igneous rocks texture and composition.”

12 of 53

Glassy Textures in an Obsidian

TP: “To analyze igneous rocks texture and composition.”

13 of 53

Obsidian on the ESRT Chart

TP: “To analyze igneous rocks texture and composition.”

14 of 53

Fine Texture in a Rhyolite

TP: “To analyze igneous rocks texture and composition.”

15 of 53

Rhyolite on the ESRT Chart

Task- Question: Predict the crystal size and texture of the extrusive igneous rock rhyolite

TP: “To analyze igneous rocks texture and composition.”

16 of 53

Vesicular Texture in a Scoria

TP: “To analyze igneous rocks texture and composition.”

17 of 53

Scoria on the ESRT Chart

Task- Quick Write: Predict the crystal size and texture of the extrusive igneous rock scoria.

TP: “To analyze igneous rocks texture and composition.”

18 of 53

Coarse = slow cooling; 1 - 10 mm mineral crystals

Individual grains can be seen with the naked eye.

Very coarse = > 10 mm mineral crystals

Intrusive Textures

TP: “To analyze igneous rocks texture and composition.”

19 of 53

Intrusive Igneous Textures

Intrusive

TP: “To analyze igneous rocks texture and composition.”

20 of 53

Coarse Texture in a Granite

TP: “To analyze igneous rocks texture and composition.”

21 of 53

Coarse Texture in a Granite

TP: “To analyze igneous rocks texture and composition.”

22 of 53

V. Coarse Texture in a Pegmatite

1 cm

TP: “To analyze igneous rocks texture and composition.”

23 of 53

Coarse Texture in a Granite

TP: “To analyze igneous rocks texture and composition.”

24 of 53

Task- Question: These are both intrusive rocks, but what is the most obvious difference between them?

The Textures vs. Composition

TP: “To analyze igneous rocks texture and composition.”

25 of 53

Felsic Igneous Rocks

Felsic igneous rocks have

light color (except obsidian which is black)
lower density
composition rich in silicon (Si) and Aluminum (Al)

TP: “To analyze igneous rocks texture and composition.”

26 of 53

The Textures vs. Composition

Felsic

TP: “To analyze igneous rocks texture and composition.”

27 of 53

Mafic Igneous Rocks

Mafic igneous rocks have

dark color (except obsidian which is black)
high density
composition rich in iron (Fe) and magnesium (Mg)

TP: “To analyze igneous rocks texture and composition.”

28 of 53

The Textures vs. Composition

Felsic

Mafic

Intermediate

TP: “To analyze igneous rocks texture and composition.”

29 of 53

Task- Question: What in an igneous rock actually gives it all of its texture and composition?

What Makes the Composition?

Andesite Macroscopic

Andesite Microscopic

1 millimeter

TP: “To analyze igneous rocks texture and composition.”

30 of 53

Igneous Mineral Compositions

TP: “To analyze igneous rocks texture and composition.”

31 of 53

Finding % Mineral Compositions

TP: “To analyze igneous rocks texture and composition.”

32 of 53

Finding % Mineral Compositions

TP: “To analyze igneous rocks texture and composition.”

33 of 53

Potassium Feldspar- __________

Quartz- __________

Plagioclase Feldspar- __________

Biotite Mica- __________

Amphibole- __________

Total %- ___100%___

Finding % Mineral Compositions

TP: “To analyze igneous rocks texture and composition.”

34 of 53

Finding % Mineral Compositions

TP: “To analyze igneous rocks texture and composition.”

35 of 53

Finding % Mineral Compositions

Potassium Feldspar

Quartz

Plagioclase Feldspar

Biotite

Amphibole

TP: “To analyze igneous rocks texture and composition.”

36 of 53

Finding % Mineral Compositions

TP: “To analyze igneous rocks texture and composition.”

Potassium Feldspar

Quartz

Plagioclase Feldspar

Biotite

Amphibole

37 of 53

Potassium Feldspar- ___25%____

Quartz- __________

Plagioclase Feldspar- __________

Biotite Mica- __________

Amphibole- __________

Total %- ___100%___

Finding % Mineral Compositions

TP: “To analyze igneous rocks texture and composition.”

38 of 53

TP: “To analyze igneous rocks by their composition.”

Finding % Mineral Compositions

Potassium Feldspar (25%)

Quartz

Plagioclase Feldspar

Biotite

Amphibole

39 of 53

Potassium Feldspar- ___25%____

Quartz- ___40%____

Plagioclase Feldspar- __________

Biotite Mica- __________

Amphibole- __________

Total %- ___100%___

Finding % Mineral Compositions

TP: “To analyze igneous rocks by their composition.”

40 of 53

TP: “To analyze igneous rocks by their composition.”

Finding % Mineral Compositions

Potassium Feldspar (25%)

Quartz (40%)

Plagioclase Feldspar

Biotite

Amphibole

41 of 53

Potassium Feldspar- ___25%____

Quartz- ___30%____

Plagioclase Feldspar- ___20%____

Biotite Mica- __________

Amphibole- __________

Total %- ___100%___

Finding % Mineral Compositions

TP: “To analyze igneous rocks by their composition.”

42 of 53

TP: “To analyze igneous rocks by their composition.”

Finding % Mineral Compositions

Potassium Feldspar (25%)

Quartz (40%)

Plagioclase Feldspar (20%)

Biotite

Amphibole

43 of 53

Potassium Feldspar- ___25%____

Quartz- ___40%____

Plagioclase Feldspar- ___20%____

Biotite Mica- ___10%____

Amphibole- __________

Total %- ___100%___

Finding % Mineral Compositions

TP: “To analyze igneous rocks by their composition.”

44 of 53

TP: “To analyze igneous rocks by their composition.”

Finding % Mineral Compositions

Potassium Feldspar (25%)

Quartz (40%)

Plagioclase Feldspar (20%)

Biotite (10%)

Amphibole

45 of 53

Potassium Feldspar- ___25%____

Quartz- ___40%____

Plagioclase Feldspar- ___20%____

Biotite Mica- ___10%____

Amphibole- ___5%____

Total %- ___100%___

Finding % Mineral Compositions

TP: “To analyze igneous rocks by their composition.”

46 of 53

Cinematographic Lava in Hawaii

TP: “To analyze the processes that make the three rock types.”

47 of 53

Mid-Lesson Assessments

TP: “To analyze igneous rocks by where they form.”

Try your best not to use the notes to answer the questions. Have your notes available in case you need to refer to it.

When you see the answer you think is correct keep your answer to yourself.

Wait until the entire class is done, and do not change your answer based on others!

48 of 53

____ Slow cooling ______ Fast cooling _____ Very fast cooling ____ Highly gaseous lava

Intrusive _________________ Extrusive ____________________

Lesson Assessment Question

TP: “To analyze igneous rocks by where they form.”

Match the appropriate rock with the correct description.

49 of 53

Regents Assessment Question

2. Obsidian’s glassy texture indicates that it formed

a. slowly, deep below Earth’s surface

b. slowly, on Earth’s surface

c. quickly, deep below Earth’s surface

d. quickly, on Earth’s surface

TP: “To analyze igneous rocks by where they form.”

50 of 53

Regents Assessment Question

TP: “To analyze igneous rocks by where they form.”

2. The photograph below shows the intergrown crystals of a pegmatite rock. Which characteristic provides the best evidence that this pegmatite solidified deep underground?

a. low density

b. light color

c. felsic composition

d. very coarse texture

51 of 53

Regents Assessment Question

TP: “To analyze igneous rocks by where they form.”

52 of 53

Regents Assessment Question

TP: “To analyze igneous rocks by where they form.”

53 of 53

Let’s Review in Groups

In your group, go back into your notes and make a list of the three (3) most important concepts we learned today. Place those the three in order from the most important concept to least important.

TP: “To analyze igneous rocks by where they form.”