Chapter 3 Igneous Rocks

1. Chapter 3Igneous Rocks

2. QUIZ!!! • Define a rock. • What drives plate tectonics? • What are the 3 rock types? • What processes (4) change an igneous rock to a sedimentary rock? • __________ and __________ are necessary for an igneous rock to form. • __________ and ___________ are necessary for a metamorphic rock to form.

3. 7. What igneous rock texture means that the magma had volatiles? 8. ________ is an igneous texture with small crystals. 9. ________ is an igneous texture with large crystals. 10. Small or Large crystals form from fast cooling. 11. Describe the geothermal gradient (text definition and numerical).

4. C to F = (C 9/5) +32 F to C = (F-32) 5/9 • 650* C to F • 1500* F to C • 27,000* F to C

5. MEET YOUR ROCKS…. • Please choose 1 rock from each category and tell me what they all have in common. • Can you tell me anything about the environment in which these rocks were formed by looking at them? • How about my examples? Discuss…

6. Basics of Geology: BELL WORK • Every _______is a Record of the Environment in Which It Formed.

7. WHAT IS A ROCK?

8. Rocks • Arockis a naturally formed, consolidated material usually composed of grains of one or more minerals • Earth materials are ever changing because of earth’s internal heat engine.

9. The earth’s internal heat is driven by….? A. Mr. Barbetta B. Radioactive Decay in the core C. Conduction and Convection

10. Radioactive decay in the core! • Mr. Barbetta is the driving force behind many great scientific anomalies, but not earth’s internal heat. • Conduction and convection disperse the heat but do not create it.

11. So…where do rocks originate?

12. Bell work 11-16-10 • How do bits of minerals end up as rock? • Sedimentary rocks are formed by___________. • Metamorphic rocks are formed by __________. • Igneous rocks are formed by ___________.

13. QUIZ • Define MINERAL. • Define ROCK. • What fuels the internal heat engine? • How is heat transferred inside the Earth? • Who is your favorite science teacher?

14. So how do bits of minerals end up as rock? The rock cycleshows how one type of rocky material gets transformed into another • Sedimentary • Metamorphic • Igneous

15. BONUS! • SW PA BEDROCK IS SEDIMENTARY. • CYCLIC SEQUENCES OF: • Sand and Siltstone • Limestone • Shale • Coal

16. Sedimentary Rock is formed by: • Lithification of sediment • ? Is LITHIFICATION? • -The turning of sediment into rock by Compaction and cementation

17. Metamorphic Rock is formed by: • High Heat and Pressure

18. Magma is formed by: • Melting

19. Igneous Rock is formed by: • cooling & rising of magma

20. Sediment is formed by: • Weathering, erosion and transportation

21. The Rock Cycle • Magma is created by melting of rock • Less dense magma rises and cools to form igneous rock • Igneous rock exposed at surface gets weathered into sediment • Sediments transported to low areas, buried and hardened into sedimentary rock • Sedimentary rock heated and squeezed at depth to form metamorphic rock • Metamorphic rock may heat up and melt at depth to form magma Convergent plate boundary

22. The Rock Cycle

23. Plate Tectonic Diagram • http://www.classzone.com/books/earth_science/terc/content/investigations/es0602/es0602page02.cfm • Very helpful for steps in the rock cycle.

24. Bell work: 1-9-17Explain what magma is made of and its role in the rock cycle.

25. Bell work : Please explain to me what happens as you go deeper into the earth?

26. ANSWER! • As you travel deeper into the earth – temperature rises and so does pressure. • The farthest any human has traveled into the earth is Kola peninsula, Russia 12,262 meters (40,230 ft) in 1989, and is the deepest hole ever drilled, and the deepest point on the earth.

27. Characteristics of magma • Igneous rocks form as molten magma cools and solidifies • General Characteristic of magma • Parent material of igneous rocks • Forms from melting of rocks inside the Earth • Magma that reaches the surface is called lava

28. Characteristics of magma • General Characteristic of magma • Rocks formed from lava at the surface are classified as extrusive, or volcanic rocks • Rocks formed from magma that crystallizes at depth are termed intrusive, or plutonic rocks

29. Characteristics of magma • The nature of magma • Consists of three components: • A liquid portion, called melt, that is composed of mobile ions • Solids, if any, are silicate minerals that have already crystallized from the melt • Volatiles, which are gases dissolved in the melt, including water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2)

30. Characteristics of magma • Crystallization of magma • Texture in igneous rocks is determined by the size and arrangement of mineral grains • Igneous rocks are typically classified by • Texture • Mineral composition

31. Quiz!!!!! Define the following MAFIC FELSIC • LAVA • MAGMA • EXTRUSIVE • INTRUSIVE • PLUTONIC • VOLCANIC

32. Igneous textures • Factors affecting crystal size • Rate of cooling • Slow rate promotes the growth of fewer but larger crystals - PHANERITIC • Fast rate forms many small crystals - APHANITIC • Very fast rate forms glass • Amount of dissolved gases – if it has gasses escaping then it will have bubble holes – vesicles or a VESICULAR texture

33. Aphanitic Texture • Fine grain size, <1mm • Microscopic crystals indicate quick cooling • May have vesicles (bubble holes) Rhyolite

34. Aphanitic texture

35. Phaneritic Texture • Coarse grains, large enough to see with the naked eye. • 1-10 mm • Result of slow cooling Granite

36. Phaneritic texture Phaneritic

37. Quick Quiz • Which is which?

38. Porphyritic • Porphyritic texture • Minerals form at different temperatures as well as differing rates • Large crystals, called phenocrysts, are embedded in a matrix of smaller crystals, called the groundmass • Differential cooling first slow – then fast

39. Porphyritic texture

40. Glassy Texture • Glassy - Instantaneous cooling – looks like glass, no crystals can be seen. • Obsidian • What Type of fracture? • PUMICE is obsidian with • vesicles

41. Newberry Caldera Obsidian Flow

42. Igneous textures • Types of igneous textures • Pyroclastic texture • Various fragments ejected during a violent volcanic eruption • Textures often appear to more similar to sedimentary rocks • Pegmatitic texture • Exceptionally coarse grained • Form in late stages of crystallization of granitic magmas

43. Pyroclastic Texture

44. Igneous Compositions • Felsic (feldspar and silica) rocks are composed of light colored minerals • Light (or nonferromagnesian) silicates • Quartz • Muscovite mica • Feldspars • Major constituents of continental crust

45. Igneous Compositions • Mafic (magnesium and ferrum, for iron) rocks contain dark silicates and calcium-rich feldspars • Dark (or ferromagnesian) silicates • Olivine • Pyroxene • Amphibole • Biotite mica • Comprise the ocean floor as well as many volcanic islands

46. Igneous compositions • Other compositional groups • Intermediate composition • Contain at least 25 percent dark silicate minerals • Associated with explosive volcanic activity • Ultramafic composition • Rare composition that is high in magnesium and iron • Composed entirely of ferromagnesian silicates

47. Based on what you learned yesterday….. • Bell work: Volatiles are the dissolved gasses in magma – what does the amount of dissolved gasses mean to the level of explosivity of a volcano – how can you justify this answer?

48. Igneous Rock Chart

49. Igneous compositions • Naming igneous rocks – felsic rocks • Granite • Phaneritic • Over 25 percent quartz, about 65 percent or more feldspar • May exhibit a porphyritic texture • Very abundant as it is often associated with mountain building • The term granite covers a wide range of mineral compositions

50. Granite