Chapter 6 study guide (and igneous rocks)
1. Define volcano
a. ANY WEAK SPOT IN Earth’s crust from which lava comes out (or erupts)
2. Where are most volcanoes found?
a. Most volcanoes are found at plate boundaries; either convergent or divergent
3. What are two types of plate boundaries where volcanoes form and how does Earth’s
crust move at these boundaries?
a. Convergent boundaries produce volcanoes and occur where 2 lithospheric
plates are moving towards each other
b. Divergent boundaries produce volcanoes and occur where 2 lithospheric plates
are moving away from each other
4. What is a hot spot?
a. A hot spot forms when there is a concentration of radioactive material in Earth’s
mantle. It super-heats the part of the mantle directly above it, it melts and rises
toward the crust, burning a hole through the crust and producing a volcano.
Hot Spot volcanoes do NOT form on plate boundaries
5. How do hot spots form volcanoes?
a. A hot spot forms when there is a concentration of radioactive material in Earth’s
mantle. It super-heats the part of the mantle directly above it, it melts and rises
toward the crust, burning a hole through the crust and producing a volcano.
6. What is the main “thing” magma needs to contain in order to rise to the surface?
a. Magma needs gasses trapped within it.
7. What is silica?
a. Silica is a mineral that is found in a lot of magma. It is also known as the mineral
“QUARTZ”
8. What 2 things do silica do to magma?
a. Silica will make lava light in color
b. Silica will make lava thick, sticky, and explosive
9. Magma that does not contain a lot of silica is___ and ___
a. Black
b. Runny
10. If a volcano erupts quietly, what 2 types of lava flows will it have?
a. Pahoehoe
b. Aa
11. If a volcano erupts explosively, what will it produce in addition to (sometimes) lava
flows?
a. A volcano that erupts explosively will produce a pyroclastic flow which consists
of
i. Ash
ii. Cinders
iii. Blocks/bombs
12. What type of volcano forms from quiet eruptions?
a. A volcano that erupts quietly is a shield volcano such as Hawaii
13. What is the … of this type of volcano
a. Temperature
i. The temperature of the lava of a shield volcano is hot
b. Color
i. The color of the lava of a shield volcano is dark/black
c. Thickness
i. The thickness of the lava of a shield volcano very runny
14. What type of volcano forms from an explosive eruption without any lava flows?
a. The type of volcano that forms from only pyroclastic material such as ash,
cinders, blocks, and bombs is a cinder cone
15. What is the … of this type of volcano
a. Temperature
i. The temperature of the lava of a cinder cone volcano is cool
b. Color
i. The color of the lava of a cinder cone volcano is light
c. Thickness
i. The thickness of the lava of cinder cone volcano very thick
16. What type of volcano forms from an explosive eruption with lava flows?
a. The type of volcano that forms from alternating layers of lava and pyroclastic
materials such as ash, cinders, blocks, and bombs is a composite volcano
17. What is the … of this type of volcano
a. Temperature
i. The temperature of the lava of a composite volcano volcano is cool
b. Color
i. The color of the lava of a composite volcano is light
c. Thickness
i. The thickness of the lava of composite volcano thick
18. If a volcano erupts explosively, what will it produce in addition to (sometimes) lava
flows?
a. A pyroclastic flow that contains ash, cinders, blocks and bombs.
19. What type of volcano forms from quiet eruptions?
b. A shield volcano
20. What type of volcano forms from an explosive eruption without any lava flows?
c. A cinder-cone volcano
21. What type of volcano forms from an explosive eruption with lava flows?
d. A composite volcano
22. Give an example of a popular shield volcano.
e. Hawaii
23. What is a pyroclastic flow?
f. A super-hot, dense, cloud of ash, cinders, blocks, and bombs that gets erupted
from composite and cinder-cone volcanoes when they erupt explosively
24. What are the three stages a volcano can move through?
g. Active
h. Dormant
i. Extinct
25. Describe each of these phases
j.
Active: an active volcano is capable of erupting soon, is currently erupting, or
has erupted in the recent past
k. Dormant: a volcano is dormant if it is capable of erupting but has not erupted
for a long time. Some volcanoes can be dormant for hundreds of years before
they begin to actively erupt again.
l. Extinct: A volcano is considered extinct if the magma in the magma chamber,
pipes, and elsewhere has hardened into rock so it is no longer capable of
erupting and will never erupt again.
26. Other types of volcanic activity include hot springs and geysers. Explain the difference
between a hot spring and a geyser?
m. A hot spring occurs when water heated by volcanic magma chambers rises to
the surface and pools on the ground. A geyser occurs when water is heated by
volcanic magma chambers rise up and are under pressure. When the pressure is
released, the hot water gets ejected into the air.
27. List 3 kinds of hazards associated with volcanoes
n. Lava flows
o. Pyroclastic flows
p. Property destruction
28. How does a caldera form?
q. A caldera forms when a volcano erupts so explosively that it empties its magma
chamber, the empty magma chamber can’t support the weight of the
overlying volcano and collapses in on itself.
29. What is a batholith?
r. A hardened magma chamber
30. What is a dike?
s. A vertical igneous intrusion. When magma cuts across layers of rock and
hardens
31. What is a sill?
t. A horizontal igneous intrusion. When magma squeezes in between rock layers
and hardens
32. What is a volcanic neck?
u. When magma hardens in the main pipe of the volcano and turns to rock. The
volcano erodes away leaving the rock that was hardened in the pipe behind.
33. What type of volcano is made of ONLY ash, cinders, blocks and bombs?
v. A cinder cone volcano
34. What type of volcano is made from ash, cinders, blocks and bombs AND lava flows?
w. A composite volcano
35. What type of volcano is made of thin, runny lava flows?
x. A shield volcano
36. What is a lava plateau?
y. A lava plateau is formed from a rift eruption of runny lava. A long crack in rock
has runny lava flow out of it over and over creating a large area high above sea
level created by successive running lava flows
37. Why is geothermal energy so awesome?
z. Because it’s renewable and does not produce pollution from fossil fuels!