2. Chapter Menu Lesson 1: Volcanoes and Plate Boundaries
Lesson 2: Volcanic Eruptions and Features
Lesson 3: Hazards of Volcanic Eruptions
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3. 7.1 Volcanoes and Plate Boundaries
vent
fissure eruption
hot spot

4. 7.1 Volcanoes and Plate Boundaries
What is a volcano?
A volcano is a land or underwater feature that forms when magma reaches the surface of Earth.
Volcanoes can cause the eruption of liquid, gas, and/or solid materials.

5. What is a volcano? (cont.)

6. 7.1 Volcanoes and Plate Boundaries
How do volcanoes form?
When rocks become hot enough and conditions are right, they can melt.
Magma is less dense than surrounding rock.
Magma rises towards Earth’s surface because of the buoyant force pushing up.

7. Convergent Plate Boundaries
7.1 Volcanoes and Plate Boundaries
Convergent Plate Boundaries
Volcanoes tend to erupt more violently.
Volcanic arcs—form when an oceanic plate subducts beneath a continental plate
Island arcs—form when two oceanic plates move toward each other

8. Divergent Plate Boundaries
7.1 Volcanoes and Plate Boundaries
Divergent Plate Boundaries
Eruptions can occur in either the ocean, as a mid-ocean ridge, or on a continent, as a continental rift.
Magma reaches Earth’s surface as fissure eruptions.

9. 7.1 Volcanoes and Plate Boundaries
Heat Escapes
Magma erupts through a circular or oval opening of a volcano, called a vent.
Fissure eruptions occur when magma escapes through narrow and elongated cracks in Earth’s crust.

10. Volcanoes Away from Plate Boundaries
7.1 Volcanoes and Plate Boundaries
Volcanoes Away from Plate Boundaries
Not all volcanoes occur along plate boundaries.
Hot spots are localized areas of high heat in Earth’s interior.
Hawaiian Islands

11. Where do volcanoes occur?
7.1 Volcanoes and Plate Boundaries
Where do volcanoes occur?

12. What causes magma to rise toward Earth’s surface? A temperature
7.1 Volcanoes and Plate Boundaries A B C D
What causes magma to rise toward Earth’s surface?
A temperature
B cooling water
C erosion
D buoyant force
Lesson 1 Review

13. Fissure eruptions occur when?
7.1 Volcanoes and Plate Boundaries A B C D
Fissure eruptions occur when?
A magma escapes through cracks in Earth’s crust
B magma escapes through the vent
C magma does not reach Earth’s surface
D magma flows slowly
Lesson 1 Review

14. Volcanic arcs form _____.
7.1 Volcanoes and Plate Boundaries A B C D
Volcanic arcs form _____.
A when two oceanic plates are pushed together
B when two continental plates are pushed together
C when an oceanic plate sinks beneath a continental plate
D when a continental plate sinks beneath an oceanic plate
Lesson 1 Review

15. End of Lesson 1

16. 7.2 Volcanic Eruptions and Features
viscosity
shield volcano
cinder cone volcano
tephra
composite volcano

17. What controls volcanic eruptions?
7.2 Volcanic Eruptions and Features
What controls volcanic eruptions?
The composition of magma controls how lava flows and the way a volcano erupts.
The percentage of silica and oxygen in magma is related to the energy of a volcanic eruption.

18. 7.2 Volcanic Eruptions and Features
Composition of Magma
Viscosity is a physical property that describes the material’s resistance to flow.
How does magma’s composition affect a volcano’s eruption?

19. Dissolved Gases and Temperature
7.2 Volcanic Eruptions and Features
Dissolved Gases and Temperature
The higher the temperature of magma, the more easily it flows.
The more gas present in magma, the more explosive the eruption.
Most dissolved gas in magma is water vapor.

20. Types of Magma and Lava Basaltic Magma and Lava
7.2 Volcanic Eruptions and Features
Types of Magma and Lava
Basaltic Magma and Lava
Low percentage of silica
Low viscosity
Produces quiet, non-explosive eruptions

21. Types of Magma and Lava (cont.)
7.2 Volcanic Eruptions and Features
Types of Magma and Lava (cont.)
Granitic Magma and Lava
High percentage of silica
High viscosity
Tends to trap gases and produce explosive eruptions

22. Types of Volcanoes Shield Volcanoes
7.2 Volcanic Eruptions and Features
Types of Volcanoes
Shield Volcanoes
Huge, gently sloping volcanic landform
Mainly composed of basaltic lava
Hawaiian Islands are an example

23. Types of Volcanoes (cont.)
7.2 Volcanic Eruptions and Features
Types of Volcanoes (cont.)
Cinder Cone Volcanoes
Cone shaped
Mainly composed of solid fragments called tephra
Typically produce explosive eruptions

24. Types of Volcanoes (cont.)
7.2 Volcanic Eruptions and Features
Types of Volcanoes (cont.)
Composite Volcanoes
Forms tall, majestic mountains
Mainly composed of alternating layers of lava and tephra
Typically produce alternating quiet and explosive eruptions

25. Types of Volcanoes (cont.)
7.2 Volcanic Eruptions and Features
Types of Volcanoes (cont.)

26. Volcanoes in California
7.2 Volcanic Eruptions and Features
Volcanoes in California
A variety of active volcanoes occur along the western coast of the United States.
Form at convergent plate boundary as part of a volcanic arc

27. Intrusive Volcanic Features
7.2 Volcanic Eruptions and Features
Intrusive Volcanic Features
Types of intrusive features include:
batholiths—largest intrusive features
sills—magma that is parallel to rock layers and hardens
dikes—magma that cuts across rock layers and hardens
volcanic necks

28. Intrusive Volcanic Features
7.2 Volcanic Eruptions and Features
Intrusive Volcanic Features

29. Other Volcanic Features
7.2 Volcanic Eruptions and Features
Other Volcanic Features
Volcanic neck—erosion wears away the volcano and leaves behind the hardened vent
Lava domes—forms when a mass of highly viscous lava slowly erupts from the vent
Lava tubes—a hollow tube that forms when lava flows through a channel, cools, and hardens on the surface
Caldera—a large, circular depression that forms when the tops of a volcano collapses

30. Other Volcanic Features (cont.)
7.2 Volcanic Eruptions and Features
Other Volcanic Features (cont.)

31. D low gas concentration
7.2 Volcanic Eruptions and Features A B C D
Which characteristics of magma would likely result in an explosive eruption?
A low viscosity
B high viscosity
C high temperature
D low gas concentration
Lesson 2 Review

32. Which type of volcano is mainly composed of tephra? A caldera
7.2 Volcanic Eruptions and Features A B C D
Which type of volcano is mainly composed of tephra?
A caldera
B composite
C cinder cone
D shield
Lesson 2 Review

33. Which is the largest intrusive volcanic feature? A dike B lava dome
7.2 Volcanic Eruptions and Features A B C D
Which is the largest intrusive volcanic feature?
A dike
B lava dome
C lava tube
D batholith
Lesson 2 Review

34. End of Lesson 2

35. 7.3 Hazards of Volcanic Eruptions
volcanic ash
lahar
pyroclastic flow

36. Volcanic Ash Volcanic ash is a very fine grained tephra.
7.3 Hazards of Volcanic Eruptions
Volcanic Ash
Volcanic ash is a very fine grained tephra.
Composed of tiny, sharp mineral and glasslike particles
Affects humans and wildlife habitats by burying plants and animals and their food sources and contaminating the water supply.

37. 7.3 Hazards of Volcanic Eruptions
Lahars
A lahar is a rapidly flowing mixture of volcanic debris and water.
Some large lahars begin as landslides.
A fast-moving lahar provides little time for warning.

38. 7.3 Hazards of Volcanic Eruptions
Gas Emissions
Gas released from volcanic eruptions can be a silent hazard to humans and wildlife.
Sulfur dioxide and hydrogen sulfide gases, when mixed with water, can form sulfuric acid precipitation.

39. Pyroclastic Flows A fast-moving body of hot gases and solids
7.3 Hazards of Volcanic Eruptions
Pyroclastic Flows
A fast-moving body of hot gases and solids
Can burn and destroy all forms of life in its path
Typically produced during explosive eruptions
Tend to follow valleys

40. Lava Flows Occur from either an explosive or quiet volcanic eruption
7.3 Hazards of Volcanic Eruptions
Lava Flows
Occur from either an explosive or quiet volcanic eruption
Destroy human and wildlife habitats by starting fires and releasing smoke
Move slowly enough that humans can be warned of possible dangers

41. Predicting Volcanic Eruptions
7.3 Hazards of Volcanic Eruptions
Predicting Volcanic Eruptions
Volcanoes usually show signs of activity before an eruption. These signs include:
small earthquakes
gas emissions
changes in ground movement and temperature around the volcano

42. Which location would be vulnerable to pyroclastic flows?
7.3 Hazards of Volcanic Eruptions A B C D
Which location would be vulnerable to pyroclastic flows?
A on a hill several miles away.
B in a river valley downstream from a volcano.
C in a commercial jet flying near a volcano.
D none of the above
Lesson 3 Review

43. What is a fast-moving body of hot gases and solids? A dike B ash cloud
7.3 Hazards of Volcanic Eruptions A B C D
What is a fast-moving body of hot gases and solids?
A dike
B ash cloud
C lahar
D pyroclastic flow
Lesson 3 Review

44. What is not a sign of a possible volcanic eruption?
7.3 Hazards of Volcanic Eruptions A B C D
What is not a sign of a possible volcanic eruption?
A frequency of small earthquakes increases
B decline in gas emissions
C increase in ground temperature
D slight bulge in the ground surface
Lesson 3 Review

45. End of Lesson 3

46. Chapter Resources Menu
Chapter Assessment
California Standards Practice
Concepts in Motion
Image Bank
Science Online
Interactive Table
Virtual Lab
Click on a hyperlink to view the corresponding feature.

47. What causes magma to rise to the Earth’s Surface? B C D
What causes magma to rise to the Earth’s Surface?
A Magma is more dense than surrounding rock and is pushed up by conductive forces.
B Magma is less dense than surrounding rock and is pushed up by conductive forces.
C Magma is more dense than surrounding rock and is pushed up by buoyant forces.
D Magma is less dense than surrounding rock and is pushed up by buoyant forces.
Chapter Assessment 1

48. Which properties occur in lava with a high percentage of silica? B C D
Which properties occur in lava with a high percentage of silica?
A thinner, slow moving, high viscosity
B thicker, slow moving, high viscosity
C thicker, fast moving, high viscosity
D thicker, slow moving, low viscosity
Chapter Assessment 2

49. A sulfur dioxide and hydrogen sulfide B ozone and sulfur dioxide C D
What two gases, when emitted from a volcano and mixed with water, can form sulfuric acid rain?
A sulfur dioxide and hydrogen sulfide
B ozone and sulfur dioxide
C nitrogen and hydrogen sulfide
D argon and hydrogen sulfide
Chapter Assessment 3

50. The Hawaiian Islands are an example of what type of volcano? A shield B C D
The Hawaiian Islands are an example of what type of volcano?
A shield
B cone
C pyroclastic
D composite
Chapter Assessment 4

51. What is a characteristic of magma with low viscosity? B C D
What is a characteristic of magma with low viscosity?
A erupts explosively
B thick and lumpy
C flows slowly
D thin and runny
Chapter Assessment 5

52. SCI 1.d A B C D
What forms at a divergent plate boundary when an oceanic plate sinks beneath a continental plate?
A island arc
B volcanic arc
C fissure eruption
D tephra
CA Standards Practice 1

53. The Hawaiian Islands have formed above a ____. A hot spot B island arc
SCI 1.e A B C D
The Hawaiian Islands have formed above a ____.
A hot spot
B island arc
C volcanic arc
D fissure eruption
CA Standards Practice 2

54. B Lava flows in a hollow channel.
SCI 1.f A B C D
How does a caldera form?
A The top of a volcano collapses and becomes wedged into the empty magma chamber.
B Lava flows in a hollow channel.
C A mass of thick, highly viscous lava slowly erupts from the vent.
D Magma cools slowly and solidifies before reaching the surface.
CA Standards Practice 3

55. What is a pyroclastic flow?
SCI 2.d A B C D
What is a pyroclastic flow?
A slow moving body of lava that starts fires
B a cloud of very fine-grained tephra
C a fast moving body of hot gases and solids
D a fast flow of lava that erupts from cracks in the seafloor
CA Standards Practice 4

56. What forms a composite volcano? A tephra
SCI 1.e A B C D
What forms a composite volcano?
A tephra
B alternating layers of tephra and lava
C volcanic ash
D none of the above
CA Standards Practice 5

57. Concepts in Motion 1

58. Image Bank

59. Interactive Table

60. End of Resources