1. Table of Contents Chapter 6 Volcanoes Chapter Preview
6.1 Volcanoes and Plate Tectonics
6.2 Volcanic Eruptions
6.3 Volcanic Landforms
6.4 California Geology

2. Chapter Preview Questions
Chapter 6 Volcanoes
Chapter Preview Questions
1. Igneous rocks form when
a. sediment is compacted and cemented.
b. rocks are changed by heat and pressure.
c. sediment is heated and cooled.
d. lava and magma cool and harden.

3. Chapter Preview Questions
Chapter 6 Volcanoes
Chapter Preview Questions
1. Igneous rocks form when
a. sediment is compacted and cemented.
b. rocks are changed by heat and pressure.
c. sediment is heated and cooled.
d. lava and magma cool and harden.

4. Chapter Preview Questions
Chapter 6 Volcanoes
Chapter Preview Questions
2. Melted material that erupts from a volcano is called
a. magma.
b. sediment.
c. lava.
d. mica.

5. Chapter Preview Questions
Chapter 6 Volcanoes
Chapter Preview Questions
2. Melted material that erupts from a volcano is called
a. magma.
b. sediment.
c. lava.
d. mica.

6. Chapter Preview Questions
Chapter 6 Volcanoes
Chapter Preview Questions
3. Why do volcanoes erupt?
a. They are hot and fiery.
b. They form beneath the ocean floor.
c. Gases in magma expand as it rises to the surface.
d. Lava is a pure liquid.

7. Chapter Preview Questions
Chapter 6 Volcanoes
Chapter Preview Questions
3. Why do volcanoes erupt?
a. They are hot and fiery.
b. They form beneath the ocean floor.
c. Gases in magma expand as it rises to the surface.
d. Lava is a pure liquid.

8. Chapter Preview Questions
Chapter 6 Volcanoes
Chapter Preview Questions
4. Which of these does NOT rapidly change Earth’s
land surface?
a. earthquakes
b. mountain building
c. landslides
d. volcanic eruptions

9. Chapter Preview Questions
Chapter 6 Volcanoes
Chapter Preview Questions
4. Which of these does NOT rapidly change Earth’s
land surface?
a. earthquakes
b. mountain building
c. landslides
d. volcanic eruptions

10. Chapter 6 Volcanoes What causes volcanoes, and how do they change
Earth’s surface?
You know that if you want to open a bottle of soda, you must do so carefully. Otherwise, the soda might spray out of the bottle as soon as you loosen the cap. What causes the soda to rush out with such force? How is this similar to what happens when a volcano erupts? Explain.

11. Use Clues to Determine Meaning
Chapter 6 Volcanoes
Use Clues to Determine Meaning
Unfamiliar words
Hot spot is
the subject of
the sentence.
Some volcanoes result from hot spots in Earthís mantle. A hot spot is an area where material from within the mantle rises and then melts. A volcano forms above a hot spot when the hot material erupts through the crust and reaches the surface.
A hot spot in the ocean oor can gradually form a series of volcanic mountains. For example, the Hawaiian Islands formed one by one over millions of years as the Pacific plate drifted over a hot spot.
Definition,
follows boldface
Explanation
Example

12. Chapter 6 Volcanoes Apply It!
Review the clues to the meaning of hot spot. Then complete the following.
1. What clue tells you that hot spot might be followed by a definition?
The term is in boldface and is the subject of the sentence.
2. What example helps you understand hot spots?
The Hawaiian Islands formed one by one over millions of years as the
Pacific plate drifted over a hot spot

13. Chapter 6 Volcanoes
End of Chapter Preview

14. Warm-Up
Describe what happens along a fault beneath Earth’s surface when an earthquake occurs?

15. How do volcanoes change the land?
Warm-Up
How do volcanoes change the land?

16. Volcanoes

17. Section 1: Volcanoes and Plate Tectonics
Chapter 6 Volcanoes
Section 1: Volcanoes and Plate Tectonics
Where are most of Earth’s volcanoes found?
How do hot spot volcanoes form?

18. A volcano is a weak spot in the crust where molten material, or magma, comes to the surface.

19. Magma is molten material that has not reached the surface and is still underground.

20. Lava is molten material, or magma, that has reached the surface.

21. Ring of Fire is a major volcanic belt that rims or circles the Pacific Ocean.

22. Island Arc is a string of islands formed by weak spots or hot spots in the crust where magma burns through.

23. Volcanoes and Plate Boundaries
Chapter 6 Volcanoes
Volcanoes and Plate Boundaries
Volcanic belts form along the boundaries of Earth’s plates.

24. Volcanoes and Plate Boundaries
Chapter 6 Volcanoes
Volcanoes and Plate Boundaries
Volcanoes often form where two oceanic plates collide or where an oceanic plate collides with a continental plate. In both situations, an oceanic plate sinks through a trench. Rock above the plate melts to form magma, which then erupts to the surface as lava.

25. Hot Spot Volcanoes Chapter 6 Volcanoes
A volcano forms above a hot spot when magma erupts through the crust and reaches the surface.

26. Click the PHSchool.com button for an activity about volcanoes.
Chapter 6 Volcanoes
More on Volcanoes
Click the PHSchool.com button for an activity about volcanoes.

27. End of Section: Volcanoes and Plate Tectonics
Chapter 6 Volcanoes
End of Section: Volcanoes and Plate Tectonics

28. What causes volcanoes to form at a spreading boundary?
Warm-Up
What causes volcanoes to form at a spreading boundary?

29. Where are most of Earth’s volcanoes found? Explain.
Warm-Up
Where are most of Earth’s volcanoes found? Explain.

30. Warm-Up
Describe the order of parts through which magma travels as it moves to the surface.

31. Warm-Up
Which is more likely to be dangerous – a volcano that erupts frequently or a volcano that has been inactive for a hundred years? Why?

32. Section 2: Volcanic Eruptions
Chapter 6 Volcanoes
Section 2: Volcanic Eruptions
What happens when a volcano erupts?
What are the two types of volcanic eruptions?
What are a volcano’s stages of activity?

33. Volcanic Eruptions

34. Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
When a volcano erupts, the force of the expanding gases pushes magma from the magma chamber through the pipe until it flows or explodes out of the vent.

35. Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Magma chamber is a pocket beneath a volcano where magma is collected or stored.

36. Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Pipe is a long tube inside a volcano that connects the magma chamber to the Earth’s surface.

37. Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Vent is an opening through which molten rock and gas leave the volcano.

38. Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Lava flow is the area covered by lava as it pours out of a vent.

39. Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Crater is a bowl-shaped area that may form at the top of a volcano.

40. Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Pahoehoe is a very thin, fast moving lava. Pahoehoe contains low amounts of silica, which gives it it’s thinness. When Pahoehoe hardens, it forms wrinkle and rope-like rock formations. Pahoehoe is hotter than Aa.

41. Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Aa is a very thick, slow moving lava. Aa contains high amounts of silica, which gives it it’s thickness. When aa hardens, it forms a rough surface consisting of jagged (sharp) lava chunks.

42. Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Pyroclastic flow is an explosive eruption that includes hot gases, cinders (volcanic ash), and bombs (volcanic rocks).

43. Composite Volcano Eruption Activity
Chapter 6 Volcanoes
Composite Volcano Eruption Activity
Click the Active Art button to open a browser window and access Active Art about composite volcano eruption.

44. Magma Composition Chapter 6 Volcanoes
Magma varies in composition and is classified according to the amount of silica it contains. The graphs show the average composition of the two types of magma. Use the graphs to answer the questions.

45. Magma Composition Chapter 6 Volcanoes Reading Graphs:
Study both graphs. What materials make up both types of magma?
Silica, other oxides, and other solids.

46. Magma Composition Chapter 6 Volcanoes Reading Graphs:
Which type of magma has more silica? About how much silica does this type of magma contain?
Rhyolite-forming magma; about 70 percent.

47. Magma Composition Chapter 6 Volcanoes Estimating:
A third type of magma has a silica content that is halfway between that of the other two types. About how much silica does this type of magma contain?
About 60 percent

48. Magma Composition Chapter 6 Volcanoes
Predicting:
What type of magma would have a higher viscosity? Explain.
Rhyolite-forming magma would have higher viscosity because it is higher in silica.

49. Kinds of Volcanic Eruptions
Chapter 6 Volcanoes
Kinds of Volcanic Eruptions
Within the last 150 years, major volcanic eruptions have greatly affected the land and people around them.

50. Deadly Eruptions

51. Stages of Volcanic Activity
Chapter 6 Volcanoes
Stages of Volcanic Activity
Active volcanoes are considered “live” meaning that it is erupting, or has shown signs that it may erupt in the near future
Lassen Peak
Mount Shasta

52. Stages of Volcanic Activity
Chapter 6 Volcanoes
Stages of Volcanic Activity
Dormant volcanoes are considered “asleep” or “sleeping bears” meaning that they may become active in the future
Long Valley Craters

53. Stages of Volcanic Activity
Chapter 6 Volcanoes
Stages of Volcanic Activity
Extinct volcanoes are considered “dead” meaning that it is unlikely that they will erupt again
St. Lucia
Auckland

54. End of Section: Volcanic Eruptions
Chapter 6 Volcanoes
End of Section: Volcanic Eruptions

55. Section 3: Volcanic Landforms
Chapter 6 Volcanoes
Section 3: Volcanic Landforms
What landforms do lava and ash create?
How does magma that hardens beneath the surface create landforms?

56. Types of Volcanoes

57. Landforms From Lava and Ash
Chapter 6 Volcanoes
Landforms From Lava and Ash
Volcanic eruptions create landforms made of lava, ash, and other materials. These landforms include composite volcanoes, shield volcanoes, cinder cone volcanoes, and lava plateaus.

58. Landforms From Lava and Ash
Chapter 6 Volcanoes
Landforms From Lava and Ash
Composite Volcanoes have quiet eruptions that alternate with explosive eruptions, forming layers of lava and ash.
Cotopaxi, Ecuador
Mayon, Philippines

59. Landforms From Lava and Ash
Chapter 6 Volcanoes
Landforms From Lava and Ash
Shield Volcanoes have quiet eruptions and have gentle slopes, which are not steep.
Mauna Loa, Hawaii
Erta Ale, Ethiopia

60. Landforms From Lava and Ash
Chapter 6 Volcanoes
Landforms From Lava and Ash
Cinder Cone Volcanoes have explosive eruptions of ash, cinders, and bombs that form a cone-shaped hill.
Mount Etna, Italy
SP Crater, Arizona

61. Landforms From Lava and Ash
Chapter 6 Volcanoes
Landforms From Lava and Ash
Lava Plateaus are formed from runny lava (pahoehoe) that cools in flat sheets of rock. Over time these layers form high plateaus.
Steamboat Rock, Washington
Hawaii

62. Landforms From Lava and Ash
Chapter 6 Volcanoes
Landforms From Lava and Ash
Calderas are formed when a magma chamber is emptied after an eruption and the volcano mountain collapses into the empty space creating a crater.
Aniakchak, Alaska
Crater Lake, Oregon

63. Landforms From Lava and Ash
Chapter 6 Volcanoes
Landforms From Lava and Ash
A caldera forms when an volcano’s magma chamber empties and the roof of the chamber collapses. The result is a large, bowl-shaped caldera.

64. Landforms From Magma Chapter 6 Volcanoes
Features formed by magma include volcanic necks, dikes, and sills, as well as batholiths and dome mountains.

65. Chapter 6 Volcanoes
Landforms From Magma
Batholiths

66. Chapter 6 Volcanoes
Landforms From Magma
Volcanic Necks

67. Chapter 6 Volcanoes
Landforms From Magma
Dikes

68. Chapter 6 Volcanoes
Landforms From Magma
Sills

69. Batholiths Chapter 6 Volcanoes
A batholith is a mass of rock formed when a large body of magma cools inside the crust. Several large batholiths form the core of mountain ranges in western North America. Half Dome in Yosemite National Park, California, is part of the Sierra Nevada batholith.

70. Links on Volcanic Effects
Chapter 6 Volcanoes
Links on Volcanic Effects
Click the SciLinks button for links on volcanic effects.

71. End of Section: Volcanic Landforms
Chapter 6 Volcanoes
End of Section: Volcanic Landforms

72. Section 4: California Geology
Chapter 6 Volcanoes
Section 4: California Geology
How does plate tectonics help to explain features of California’s geology?

73. Plate Tectonics and California
Chapter 6 Volcanoes
Plate Tectonics and California
The movements of three plates have shaped the geologic features of California over millions of years.

74. Plate Tectonics and California
Chapter 6 Volcanoes
Plate Tectonics and California
Many geologic processes worked together to form California’s landscape
of volcanoes, faults, mountain ranges, and basins.

75. End of Section: California Geology
Chapter 6 Volcanoes
End of Section: California Geology

76. Chapter 6 Volcanoes
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77. Chapter 6 Volcanoes
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