Chapter 3- Volcanoes Review Packet Answers
Section 3-1
1.
2.
3.
4.
5.
6.
7.
8.
9.
A volcano is a weak spot in the crust where molten rock comes to the surface.
Magma
Lava
It is a major volcanic belt formed by many volcanoes that rim the Pacific Ocean due to Subduction.
A. Divergent Plate Boundaries; B. Convergent Plate Boundaries/Subduction Zones; C. Hot Spots
Volcanoes form when lava pours out of cracks in the ocean floor.
False
True
Subduction causes slabs of oceanic crust to sink through deep ocean trenches into the mantle, where it
forms magma that rises back to the surface (because it is less dense.) When magma rises back to the
surface through cracks in the crust, volcanoes form.
10. Island arc
11. Major island arcs include Japan, New Zealand, Indonesia, the Caribbean Islands, the Philippines, the South
Sandwich Islands, the Mariana Islands and the Aleutian Islands. (You don’t need to know this for the
quest.)
12. a continental plate (South American) and an oceanic plate (Nazca)
13. A hot spot is an area where magma from deep within the mantle melts through the crust like a blow torch.
14. They formed as the pacific plate slowly moved over a hot spot.
15. False
Section 3-2
1.
2.
3.
4.
False
True
Carbon Dioxide dissolved in soda pop rushes out when the pop is opened. (It may help to shake it up!)
The gases dissolved in magma rush out of the vent carrying the magma with it. Pressure forces the magma
out.
5. Pocket of magma beneath the surface AND crack to the surface
6. Left side top: Vent, left side bottom: pipe, right side top: crater, right side very bottom: magma chamber.
7. A lava flow is the area covered by lava as it pours out of a vent.
8. A crater forms at the top of a volcano around the central vent.
9. False
10. Factors include the amount of gas dissolved in the magma, how thick or thin the magma is, its temperature
and its silica content.
11. It makes magma thicker AND It produces light colored lava
12. A
13. C
14. D
15. B
16. False
17. Pahoehoe
18. aa
19. C
20. A
21. B
22. A pyroclastic flow is an explosive eruption of ash, cinders, bombs and gasses.
23. True
24. False
25. Extinct, Active, Dormant
26. False
27. True
28. Hot spring
29. Geyser
30. Stream from deep underground spins the wheel in a turbine and the moving wheel turns a generator that
produces electricity.
31. Geologists cannot predict what type of eruption a volcano will produce.
32. They might be unaware of the danger because the time between volcanic eruptions may span hundreds of
years.
33. False
34. Volcanoes can start fires, bury towns, damage crops, clog car engines, collapse roofs, stall airplane engines
and create landslides, avalanches and mudslides.
Section 3-3
1. A- shield volcanoes, B- cinder cone volcanoes, C- composite volcanoes, D- lava plateaus
2. They form from many thin layers of lava. AND… They result from quiet eruptions.
3. False
4. Three examples are Mt. Fuji, Mt. St. Helens and Mt. Hood. (You don’t need to know this for the quest.)
5. True
6. E
7. C
8. B
9. A
10. D
11. Potassium and phosphorus (You don’t need to know this for the quest.)
12. A- volcanic neck, B- dikes, C- sills, D- batholiths, E- done mountains
13. Dike- forms across layers, Sill- forms between layers, Both- forms from magma
14. Batholith
15. An example is the batholith that forms the Sierra Nevada Mountains. (You don’t need to know this for the
quest.)
16. True.