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Chapter 6 study guide
1. Define volcano
a. Any weak spot in Earth’s crust from which magma will erupt
2. Where are most volcanoes found?
a. Most volcanoes are found on the ocean floor
3. What are two types of plate boundaries and how does the Earth’s crust move at these
boundaries?
a. Convergent boundaries (two plates move toward each other)
b. Divergent (two plates move away from each other)
4. A mid-ocean ridge forms at what type of boundary?
a. A mid ocean ridge is formed on the ocean floor at a divergent boundary
5. Island arcs form a what type of boundary?
a. An island arc forms at a convergent boundary when the oceanic plated get
subducted into the mantle
6. What is a hot spot?
a. A place where volcanoes form when an intensely hot area of the mantle causes
magma to flow up and burn a hole through the crust
7. How do hot spots form volcanoes?
a. See above
8. What is the main “thing” magma needs to contain in order to rise to the surface?
a. It needs to contain gas
9. What is silica?
a. A mineral (also known as quartz) that is found in magma and lava
10. What does silica do to magma?
a. Silica will make magma/lave light in color, cooler in temperature and thick and
sticky, causing it to get clogged in the pipes and vents of volcanoes
11. Magma that does not contain a lot of silica is __________________and _________________
a. Hot and runny and black
12. If a volcano erupts quietly, what type of lava flows will it have?
a. Pahoehoe and Aa
13. If a volcano erupts explosively, what will it produce in addition to (sometimes) lava
flows?
a. Pyroclastic flows
14. What type of volcano forms from quiet eruptions?
a. Shield
15. What type of volcano forms from an explosive eruption without any lava flows?
a. Cinder cone
16. What type of volcano forms from an explosive eruption with lava flows?
a. Composite
17. Give an example of a popular shield volcano.
a. Hawaii
18. What is a pyroclastic flow?
a. An extremely, hot, dense cloud of ash, cinders, blocks and bombs ejected from
a volcano when it erupts explosively
19. What are the three stages a volcano can move through?
a. Active, dormant and extinct
20. Describe each of these phases
a. Active: Erupting, soon to erupt, or capable of erupting in the near future
b. Dormant: Not currently erupting, may erupt in the future
c. Extinct: Will never erupt and incapable of erupting because all the magma has
hardened into rock
21. Other types of volcanic activity include hot springs and geysers. Explain the difference
between a hot spring and a geyser?
a. Hot spring is a POOL of heated water from geothermal energy
b. Geyser is an expulsion of heated water out of a vent in the crust caused by
geothermal energy
22. List 4 kinds of hazards associated with volcanoes
a. Lahars
b. Pyroclastic flows
c. Lava
d. Earthquakes
e. Avalanches
23. How does a caldera form?
a. It forms when a volcano erupts explosively, emptying it’s magma chamber and
the remnants of the volcano fall into the empty magma chamber forming a
huge crater
24. What is a batholith?
a. A magma chamber in which all the magma in it has hardened
25. What is a dike?
a. A vertical igneous intrusion
26. What is a sill?
a. A horizontal igneous intrusion
27. What is a volcanic neck?
a. The remnants of an extinct volcano
28. What type of volcano is made of ONLY ash, cinders, blocks and bombs?
a. Cinder cone
29. What type of volcano is made from ash, cinders, blocks and bombs AND lava flows?
a. Composite volcano
30. What type of volcano is made of thin, runny lava flows?
a. Shield volcano
31. What is the difference between continental and oceanic crust?
a. Continental crust is thick but less dense and buoyant (it will never subduct)
b. Oceanic crust makes up the ocean floor is thin and dense and gets subducted
into the mantle at convergent boundaries
32. What is it called when oceanic material gets pulled into the mantle at a convergent
boundary?
a. Subduction
33. What is a lava plateau?
a. Layers and layers of flat lava flows that create a landform high above sealevel.
Similar to a shield volcano in formation
34. MEMORIZE YOUR VOLCANO DIAGRAM!