1. Volcanic Activity Chap. 18 Notes: Resources: Magma Intrusive Activity
Volcanoes
Resources:
Section Assessments
Practice Test Questions

2. Magma

3. What it’s made of

4. What it’s made of

5. What it’s made of
Molten rock

6. What it’s made of
Molten rock
Suspended crystals of minerals

7. What it’s made of Molten rock Suspended crystals of minerals
Dissolved gases

8. What it’s made of
Factors that affect melting rock

9. Factors that affect melting rock
What it’s made of
Factors that affect melting rock
Pressure

10. Factors that affect melting rock
What it’s made of
Factors that affect melting rock
Pressure
Temperature

11. Factors that affect melting rock
What it’s made of
Factors that affect melting rock
Pressure
Temperature
Water content

12. Factors that affect melting rock
What it’s made of
Factors that affect melting rock
Pressure
Temperature
Water content
A graph

13. What is the relationship between depth and pressure?

14. For dry albite, the greater the depth the _________ the melting temperature.

15. Which type of albite, wet or dry, tends to melt at lower temperatures

16. Factors that affect melting rock Viscosity
What it’s made of
Factors that affect melting rock
Viscosity
Resistance to flow

17. Factors that affect melting rock Viscosity
What it’s made of
Factors that affect melting rock
Viscosity
Depends on _________

18. Factors that affect melting rock Viscosity
What it’s made of
Factors that affect melting rock
Viscosity
Depends on _________

19. What it’s made of
Factors that affect melting rock
Viscosity
Types of magma

20. Factors that affect melting rock Viscosity Types of magma
What it’s made of
Factors that affect melting rock
Viscosity
Types of magma
basaltic
andesitic
rhyolitic

21. Basaltic Andesitic Rhyolitic
Dark colored
Lighter colored

22. Basaltic Andesitic Rhyolitic
Dark colored
Lighter colored
Low viscosity
Higher viscosity
Intermediate

23. Basaltic Andesitic Rhyolitic
Dark colored
Lighter colored
Low viscosity
Higher viscosity
Intermediate
Low silicon content (about 50%)
Higher silicon (about 70%)

24. Basaltic Andesitic Rhyolitic
Dark colored
Lighter colored
Low viscosity
Higher viscosity
Intermediate
Low silicon content (about 50%)
Higher silicon (about 70%)
Little dissolved gas (1-2%)
Higher amount of trapped gas (4-6%)

25. Basaltic Andesitic Rhyolitic
Dark colored
Lighter colored
Low viscosity
Higher viscosity
Intermediate
Low silicon content (about 50%)
Higher silicon (about 70%)
Little dissolved gas (1-2%)
Higher amount of trapped gas (4-6%)
Less violent eruptions
More violent eruptions

26. Basaltic Andesitic Rhyolitic
Dark colored
Lighter colored
Low viscosity
Higher viscosity
Intermediate
Low silicon content (about 50%)
Higher silicon (about 70%)
Little dissolved gas (1-2%)
Higher amount of trapped gas (4-6%)
Less violent eruptions
More violent eruptions
Ex. Mt. St. Helens
Ex. Yellowstone
Ex. Mt. Kilauea, Mt. Pu’ u O’o,

27. The End

28. Intrusive Activity

29. Plutons
Intrusive igneous rock bodies formed under Earth’s crust

30. Plutons
Batholiths

31. Batholiths
Largest of the plutons (many hundreds of kilometers)

32. Batholiths Largest of the plutons (many hundreds of kilometers)
Form inside mountains

33. Batholiths Largest of the plutons (many hundreds of kilometers)
Form inside mountains
Form coarse-grained rocks

34. Batholiths
Ex. Yosemite

35. Plutons
Stocks

36. Stocks
Like batholiths, but smaller
Irregular shape

37. Plutons
Laccoliths

38. Laccoliths Intrude into rock layers Form mushroom shaped plutons
Smaller than batholiths and stocks

39. Laccoliths
Ex. Bear Butte, SD

40. Plutons
Sills

41. Sills Magma squeezes into cracks Forms parallel to parent rock
May be cm. to hundreds of cm. thick

42. Sill
Ex. Palisades, NJ

43. Plutons
Dike

44. Dike
Like a sill but it cuts across rock layer
Transports magma

45. Dike
Ex. Radial Dike, NM

46. The End

47. Volcanoes
Krafla, Iceland

48. Parts of a volcano

49. Parts of a volcano
Vent
Opening in the Earth’s crust that carries lava to the surface

50. Parts of a volcano Vent Crater
Bowl shaped depression at the top of a volcano.

51. Parts of a volcano Vent Crater Caldera Crater Lake, Oregon
Volcanic depression that forms above the magma chamber when the ground above sinks

52. How a caldera forms

53. Types of Volcanoes Shield Volcano Mauna Loa, Hawaii
Broad, flat volcano that forms from basaltic magma.

54. Types of Volcanoes Cinder-Cone Volcano Cinder Cone, California
Small, steep volcano that forms when ejected material falls back near the volcano’s vent

55. Types of Volcanoes Composite Volcano (Stratovolcano) Java, Indonesia
Large, steep volcano composed of alternating layers of lava and volcanic fragments.

56. Comparison of Volcano Types

57. Volcanic Material

58. Volcanic Material Tephra
Rock fragments thrown in the air during a volcanic eruption.

59. Volcanic Material
Tephra
Dust - less than 0.25 mm

60. Volcanic Material
Tephra
Dust - less than 0.25 mm
Ash – less than 2 mm

61. Volcanic Material Tephra Dust - less than 0.25 mm Ash – less than 2 mm
Lapilli (little stones) – less than 64 mm

62. Volcanic Material Tephra Dust - less than 0.25 mm Ash – less than 2 mm
Lapilli (little stones) – less than 64 mm
Volcanic block – large angular fragment

63. Volcanic Material Tephra Dust - less than 0.25 mm Ash – less than 2 mm
Lapilli (little stones) – less than 64 mm
Volcanic block – large angular fragment
Volcanic bombs – rounded blobs

64. Volcanic Material Tephra Pyroclastic flow
Clouds of gas, ash, and tephra that travel rapidly down a volcano.

65. Location of Volcanoes

66. Location of Volcanoes Convergent Boundaries
80% of volcanoes. These regions are the Circum-Pacific and Mediterranean belts.

67. Location of Volcanoes Convergent Boundaries Divergent Boundaries
Smaller percentage of volcanoes form here. Most, except Iceland, are under the sea.

68. Location of Volcanoes Convergent Boundaries Divergent Boundaries
Hot Spots
Unstable hot regions of the Earth’s mantle where high-temperature plumes rise toward surface

69. Analyzing Hot Spots

70. The End

71. Section Assessments

72. Section Assessment – 18.1
1. Match the magma types with their characteristics.
___ basaltic
___ andesitic
___ rhyolitic
A. intermediate viscosity content, forms from oceanic crust and oceanic sediments
B. low viscosity and gas content, forms from rocks in the upper mantle
C. high viscosity, forms from continental crust materials B A C

73. Section Assessment – 18.1
2. What would be the likely effect if the volcano at Yellowstone National Park were to erupt? Why?
It would most likely be a devastating eruption because it would be fueled by rhyolitic magma, which has a very high viscosity and gas content.

74. Section Assessment – 18.1
3. Identify whether the following statements are true or false.
______ It is unlikely that Mount Kilauea in Hawaii will explosively erupt.
______ Wet granite will melt at a lower temperature than dry granite.
______ A liquid with a high viscosity will also have a high flow rate.
______ Major eruptions of Mount St. Helens in Washington state and Mount Fuji in Japan would probably be similar in nature.
true
false

75. Section Assessment – 18.2
1. Match the following terms with their definitions.
___ batholith
___ stock
___ laccolith
___ sill
___ dike
A. a pluton that forms when magma intrudes parallel to layers of rock
B. an irregularly shaped pluton that is similar to a batholith but smaller in size
C. a pluton that cuts across preexisting rocks
D. an irregularly shaped pluton that covers at least 100 km2
E. a mushroom-shaped pluton with a round top and flat bottom D B E A C

76. Section Assessment – 18.2 2. How do sills and laccoliths differ?
Sills and laccoliths both result from magma intrusions that are parallel to existing rock. Laccoliths push the overlying layers upward, creating a distinct mushroom-shape when they cool and solidify. Sills are generally thinner and do not cause a noticeable bump in the surface.

77. Section Assessment – 18.2
3. What surface feature are batholiths most associated with?
Batholiths are found at the cores of many of Earth’s mountain ranges.

78. Section Assessment – 18.3
1. Match the following terms with their definitions.
___ vent
___ crater
___ tephra
___ pyroclastic flow
___ caldera
A. an opening in the crust from which lava flows
B. depression caused by a collapsed magma chamber
C. a bowl-shaped depression around an opening in the crust
D. volcanic materials that are thrown into the air during a volcanic eruption
E. a cloud of rapidly moving, extremely hot volcanic material A C D E B

79. Section Assessment – 18.3
2. How can chains of volcanoes that form over a hot spot track plate movement?
The hot spot is in a fixed location. All of the volcanoes in the chain were over the hot spot when they formed. The volcanoes’ movement and the direction of the chain’s alignment indicates the movement of the plate.

80. Section Assessment – 18.3
3. Identify whether the following statements are true or false.
______ Many cinder-cone volcanoes are less than 500 m high.
______ Volcanism is more common along divergent boundaries as compared to convergent boundaries.
______ The Mediterranean Belt is also known as the “Ring of Fire”.
______ It can be 700ºC in the center of a pyroclastic flow.
true
false

82. The End