1. Understanding Earth Chapter 12: VOLCANOES Grotzinger • Jordan
Sixth Edition
Chapter 12:
VOLCANOES
© 2011 by W. H. Freeman and Company

2. Chapter 12
Volcanoes

3. About Volcanoes
Volcanoes are windows through which we can see the interior of the Earth.
Volcanoes help us understand the plate tectonic process and mantle convection.
Volcanoes are also connected to Earth’s atmosphere and hydrosphere.

4. Lecture Outline Volcanoes as geosystems
2. Lavas and other volcanic deposits
3. Eruptive styles and landforms
4. Interactions of volcanoes with other geosystems
5. The global pattern of volcanism

5. Lecture Outline
6. Volcanism and human affairs

6. ● hill or mountain made of: ● lavas ● other erupted materials
1. Volcanoes as Geosystems
● Parts of the volcano
● hill or mountain made of:
● lavas
● other erupted materials

7. ● Parts of the geosystem ● rocks ● magmas and lavas
1. Volcanoes as Geosystems
● Parts of the geosystem
● rocks
● magmas and lavas
● processes of melting and
eruption

8. Volcanic geosystem Pipe Central vent Lava flows Side vent Dike Sill
Magma
chamber
Lithosphere

9. Volcanic geosystem Magma, which originates in the asthenosphere...
Pipe
Central vent
Lava flows
Side vent
Dike
Sill
Magma
chamber
Magma, which originates in the asthenosphere...
Lithosphere

10. Volcanic geosystem ...rises through the lithosphere to form
Pipe
Central vent
Lava flows
Side vent
Dike
Sill
...rises through the
lithosphere to form
a crustal magma chamber.
Magma
chamber
Magma, which originates in the asthenosphere...
Lithosphere

11. Volcanic geosystem Lavas erupt through a central vent and
Pipe
Central vent
Lava flows
Side vent
Lavas erupt through
a central vent and
side vents,...
Dike
Sill
...rises through the
lithosphere to form
a crustal magma chamber.
Magma
chamber
Magma, which originates in the asthenosphere...
Lithosphere

12. Volcanic geosystem ...accumulating on the surface to form a volcano.
Pipe
Central vent
Lava flows
Side vent
...accumulating on
the surface to form
a volcano.
Lavas erupt through
a central vent and
side vents,...
Dike
Sill
...rises through the
lithosphere to form
a crustal magma chamber.
Magma
chamber
Magma, which originates in the asthenosphere...
Lithosphere

13. ● Functions of the geosystem ● volcanic plumbing systems
1. Volcanoes as Geosystems
● Functions of the geosystem
● volcanic plumbing systems
● volcanoes as chemical
factories

14. Thought questions for this chapter
Give a few examples of what geologists have learned about Earth’s interior by studying volcanoes and volcanic rocks.

15. ● Types of lava ● basaltic lavas (10001200ºC) ● aa ● pahoehoe
2. Lavas and Other Volcanic Deposits
● Types of lava
● basaltic lavas (10001200ºC)
● aa
● pahoehoe
● pillow lavas

17. Pillow lavas on the sea floor

18. ● Types of lava (continued) ● andesitic lavas (<1000ºC)
2. Lavas and Other Volcanic Deposits
● Types of lava (continued)
● andesitic lavas (<1000ºC)
● rhyolitic lavas (600800ºC)

19. Mt. St. Helens’ andesitic cone

20. ● Texture of volcanic rocks ● reflect conditions under which
2. Lavas and Other Volcanic Deposits
● Texture of volcanic rocks
● reflect conditions under which
they crystallized or formed
● vesicles (bubble holes)
● glassy texture (no crystals)
● pyroclasts (broken pieces)

21. Vesicles in basalt

22. ● Texture of volcanic rocks ● pyroclastic deposits
2. Lavas and Other Volcanic Deposits
● Texture of volcanic rocks
● pyroclastic deposits
● volcanic ejecta (ash, bombs)
● pyroclastic flows (volcanic
tuffs and breccias)

23. Arenal, Costa Rica:
pyroclastic eruption

24. Volcanic ejecta bomb

25. Volcanic tuff

26. Volcanic breccia

27. Mt. Uzen, Japan:
pyroclastic ash flow

28. ● Eruptive styles and landforms
2. Lavas and Other Volcanic Deposits
● Eruptive styles and landforms
● central eruptions
● shield volcanoes
● volcanic domes
● cinder cones
● stratovolcanoes
● volcanic craters
● calderas
● diatremes

29. Eruptive styles

34. Eruptive
styles

35. Crater Lake,
Oregon

40. Ship Rock,
New Mexico
Diatreme

41. Diatreme (Ship Rock)

42. ● Eruptive styles and landforms ● eruptions from linear cracks
2. Lavas and Other Volcanic Deposits
● Eruptive styles and landforms
● eruptions from linear cracks
● fissure eruptions
● flood basalts
● ash-flow deposits

43. Fissure eruption:
Laki fissure,
Iceland

44. Sequence
of events:
formation
of a
fissure
eruption

45. Flood basalts:
Columbia
Plateau,
Washington

46. Thought questions for this chapter
Why are eruptions of stratovolcanoes generally more explosive than those of shield volcanoes?
While on a field trip, you come across a volcanic formation that resembles a field of sandbags. The individual ellipsoid forms have a smooth, glassy surface texture. What type of lava is this, and what information does this give you about its history?

47. 3. Interactions of Volcanoes
with Other Geosystems
● Volcanism and the hydrosphere
● fumaroles and geysers
● Volcanism and the atmosphere
● aerosols and ash

48. Fumarole:
Merapi volcano,
Indonesia

49. Old Faithful
geyser:
Yellowstone
National Park

50. 4. Global Pattern of Volcanism

51. ● Basalt-producing spreading centers
4. Global Pattern of Volcanism
● Basalt-producing spreading centers
● mantle source for lava (decompression melting)
● axial volcanoes of mid-ocean ridge

52. 4. Global Pattern of Volcanism

54. ● Volcanism in subduction zones ● chains of volcanoes ● island arcs
4. Global Pattern of Volcanism
● Volcanism in subduction zones
● chains of volcanoes
● island arcs
● formation of new continental
crust

55. ● Intraplate volcanism: the mantle plume hypothesis
4. Global Pattern of Volcanism
● Intraplate volcanism: the mantle
plume hypothesis
● hot spots and mantle plumes
● sea mounts and island chains
● large igneous provinces

56. 4. Global Pattern of Volcanism

58. 4. Global Pattern of Volcanism: Hawaiian Island Chain /
Emperor Seamounts

59. 4. Global Pattern of Volcanism: Yellowstone Volcanic Tracks

60. 4. Global Pattern of Volcanism: Large Igneous Provinces

61. 4. Global Pattern of Volcanism: Large Igneous Provinces

62. Thought questions for this chapter
Why are the volcanoes on the northwest side of the Hawaiian Islands dormant whereas those on the southeast side are more active?

63. ● Volcanic hazards ● lahars ● flank collapse ● caldera collapse
5. Volcanism and Human Affairs
● Volcanic hazards
● lahars
● flank collapse
● caldera collapse
● eruption clouds

64. ● Mantle-plume hypothesis ● predicting eruptions
5. Volcanism and Human Affairs
● Mantle-plume hypothesis
● predicting eruptions
● controlling eruptions

65. ● industrial materials ● ore formation ● heat energy
5. Volcanism and Human Affairs
● Natural resources
● volcanic soils
● industrial materials
● ore formation
● heat energy

66. 5. Volcanism and Human Affairs

69. 5. Volcanism and Human Affairs: Potentially Hazardous Volcanoes

71. 5. Volcanism and Human Affairs: Geothermal Energy

72. Thought questions for this chapter
What might be the effects on civilization of a Yellowstone-type caldera eruption, such as the one described at the beginning of this chapter?
How do interactions between volcanic geosystems and the climate system increase volcanic hazards?

73. Key terms and concepts Ash-flow deposit Basaltic lava Caldera Crater
Andesitic lava
Ash-flow deposit
Basaltic lava
Caldera
Crater
Diatreme
Fissure eruption
Flood basalt
Geothermal energy
Hot spot
Hydrothermal activity
Lahar
Large igneous province
Mantle plume
Pyroclastic flow

74. Key terms and concepts Stratovolcano Tuff Volcanic geosystem Volcano
Rhyolitic lava
Shield volcano
Stratovolcano
Tuff
Volcanic geosystem
Volcano