Verified Test Bank Ch4 Up from the Inferno Magma and Igneous

CHAPTER 4: Up from the Inferno: Magma and Igneous Rocks

LEARNING OBJECTIVES

4A. Distinguish between magma and lava, and explain the chemical distinctions among different types of molten rock.

4B. Describe the special places in the Earth where magma forms.

4C. Explain why melt moves to places where it solidifies, and how solidification takes place.

4D. Describe and classify different kinds of igneous rocks.

4E. Discuss where and why igneous activity happens in the context of plate tectonic theory.

MULTIPLE CHOICE

1. Igneous rocks are formed

2. The difference between magma and lava is that

3. Geologists distinguish between two main categories of igneous rock—extrusive and intrusive—based on

4. Volatiles refer to substances that

5. Important volatiles in magmas include

6. In general, when rock is partially melted, the chemistry of the melt is

7. Which type of magma has the greatest silica content?

8. A majority of the melts in the Earth form through the partial melting of ultramafic mantle rock. These newly formed magmas are

9. Felsic magmas commonly

10. The incorporation or partial melting of pieces of wall rock into a magma is termed:

11. A body of rock starts at location A in the graph below. The rock, over a period of time, moves to location B and begins to melt. This is an example of melting due to

12. The geotherm is the rate of change of

13. Adding volatiles such as water or carbon dioxide to the mantle can cause it to

14. Injecting hot fudge into ice cream and causing the ice cream to melt is an appropriate analogy for which cause of magma generation?

15. When magma solidifies below the surface of the Earth, ________ are formed.

16. If a body of magma becomes more felsic, its viscosity will

17. The linking together of silica tetrahedra into chains that do not easily move past each other affects the ________ of a magma.

18. If the volatile content of magma is increased, its viscosity will

19. During fractional crystallization of a magma body, the first mineral that is expected to crystallize from the magma will be

20. Intrusive rocks that form deep within the Earth ______________ than intrusive rocks that cool near the surface.

21. Because of its physical properties, magma tends to

22. A magma body with a ________ volume and a ________ shape cools fastest.

23. Which of the following does not affect the cooling rate of magma?

24. In the figure provided below, what type of igneous intrusion is the vertical rock unit?

25. A vast, composite intrusive igneous body that covers hundreds of square kilometers (in a map view) is called a

26. In the figure provided below, what type of igneous intrusion is the horizontal rock unit?

27. What is a xenolith?

28. The boundary formed between new intrusive igneous rock and the host rock around it is called a

29. A _________ is an irregular or blob-shaped intrusive igneous rock that formed from cooling of a magma chamber.

30. In the discontinuous series of Bowen’s reaction series, the first mineral to crystallize from a mafic melt is

31. As compared to mafic igneous rocks, felsic igneous rocks

32. A fragmental, extrusive igneous rock is referred to as which of the following?

33. A pegmatite is a coarse-grained igneous rock that forms primarily because the melt

34. As compared to coarse-grained igneous rocks, fine-grained igneous rocks

35. As compared to aphanitic igneous rocks, phaneritic rocks are

36. Igneous rocks with a glassy texture contain few if any _________.

37. An igneous rock with a mixed texture consisting of coarse crystals (phenocrysts) surrounded by fine crystals (groundmass) is termed

38. What is the term for felsic extrusive igneous rock with glassy texture?

39. Pumice and scoria are examples of glassy igneous rocks that contain a lot of ______.

40. Fragments of material erupted from a volcano eventually settle and lithify to form an extrusive igneous rock called

41. Granite, an intrusive igneous rock, is most similar in mineral composition to which extrusive equivalent?

42. A mafic, highly-vesicular volcanic rock is termed

43. Vesicles in an igneous rock are evidence for which of the following?

44. If you find a tuff in the field, what type of geologic activity could you reasonably assume has occurred?

45. The continuous series in Bowen’s reaction series describes the crystallization behavior of which mineral?

46. Igneous rocks at hot spots are formed by ________ extending deep into the Earth’s mantle.

47. Igneous rocks formed at mid-ocean ridges are primarily

48. Magma and igneous rocks formed at subduction zones originate due to _______

49. A volcanic arc results from __________ tectonic movements and is associated with a __________.

50. Flood basalts such as those found in the Columbia Plateau and the Deccan region are associated with

1. Describe the process of decompression melting. Be sure to include an example of a tectonic setting where this type of melting occurs within the Earth.

2. What is the reason for a solidus line and a liquidus line on a pressure-temperature graph in the context of partial melting and fractional crystallization?

3. Describe the difference between the relative viscosity of felsic versus mafic magma and how this affects the rate of flow of each type.

4. Briefly explain why and how magmas rise within the Earth.

5. What is fractional crystallization? Briefly explain how it works and why different types of magmas result.

6. Compare and contrast a dike and a sill. How do they relate to surrounding rock layers?

7. Rhyolite and granite are both felsic igneous rocks, although they have different cooling histories, and consequently different textures. Explain the difference between the two rock types from a cooling perspective and be specific about which igneous texture can be applied to which rock.

8. What is obsidian? How does it form?

9. What is a tuff? How does a tuff form?

10. What is the source of volatiles that lead to magma formation at subduction zones?