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Directed Reading B
Section: Volcanic Eruptions Circle the letter of the
best answer for each question.
1.What is the name of the molten rock inside a volcano?
pressure
ash
magma
lava
2. What is magma that flows onto the Earth’s surface called?
lava
magma
ash
rock
3. How are volcanoes created?
by tectonic plates colliding
by cracks in the Earth’s crust
by collections of ash and rock
by many eruptions of lava
NONEXPLOSIVE ERUPTIONS
4. Which of the following can happen during nonexplosive eruptions?
violent explosions
tons of rock blasted into the
air
huge lava flows
fire shooting into the air
Copyright © by Holt, Rinehart and Winston. All rights reserved.
EXPLOSIVE ERUPTIONS Circle the letter of the best
answer for each question.
5. Which of the following can happen during an explosive
volcanic eruption?
calm lava flows
hot debris, ash, and gas shooting into the
air
a rainbow
lava fountains
6. What is ash?
flowing lava
tiny, dust-sized bits of
rock
big chunks of rock
a gas
WHAT IS INSIDE A VOLCANO?
7. What is a vent?
a magma chamber
an eruption
a crack in the Earth’s
crust
an underground volcano
8. Where is a volcano’s magma chamber?
at the top of the vent
deep underground
on the volcano’s slope
outside the volcano
Copyright © by Holt, Rinehart and Winston. All rights reserved.
WHAT MAKES UP MAGMA? Circle the letter of the
best answer for each question.
9. What affects how explosive a volcanic eruption is?
heat
amount of lava
composition of magma
ash
Water and Magma Are an Explosive Combination
10. What is most likely to happen if the water content of
magma is high?
A nonexplosive eruption will
occur.
No eruption will occur.
Pressure will decrease.
An explosive eruption is likely.
Silica-Rich Magma Traps Explosive Gases
11. Which of the following statements is true?
Silica-rich magma has a thin, runny
consistency.
Silica-rich magma allows gases to escape easily.
Silica-rich magma causes explosive eruptions.
Silica-rich magma causes nonexplosive
eruptions.
WHAT ERUPTS FROM A VOLCANO?
12. What is pyroclastic material?
molten rock
magma that blasts into the air and
hardens
lava that flows underwater
magma that remains underground too
long
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Types of Lava Read the description. Then, draw a line from the dot next
to each
description to the matching word.
13. forms underwater in
rounded lumps
14. flows slowly, like dripping
wax 15. has a brittle, jagged
crust 16. cool, stiff lava that
forms jumbled heaps
Types of Pyroclastic Material
17. large blobs of magma that
harden in the air
18. solid rock blasted out of a
volcano
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•
•
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19. glass-like slivers from exploding
gas bubbles
20. pebblelike bits of magma that
cool in the air
Copyright © by Holt, Rinehart and Winston. All rights reserved.
a. aa lava
b. pillow lava c.
pahoehoe lava d.
blocky lava
volcanic
blocks
volcanic
bombs
lapilli
volcanic ash
Pyroclastic Flows Read the words in the box. Read the sentences. Fill in each
blank with the word that best completes the sentence.
pyroclastic temperature hurricane
21. A very dangerous type of volcanic flow is
a(n) flow.
22. Pyroclastic materials can move faster than
a(n) .
23. The center of a pyroclastic flow has a very
high .
Copyright © by Holt, Rinehart and Winston. All rights reserved.