Chapter 5 Section 2:
Volcanic Eruptions
Directions : Define the following terms.
1. Magma chamber
1. Magma collects in a pocket beneath a
volcano
2. pipe
2. A long tube through which magma
moves from the chamber to the surface.
3. vent
3. An opening through which molten rock
and gas leave a volcano.
4. Lava flow
4. The area covered by lava as it pours out
of a volcano’s vent
5. crater
5. A bowl shaped area that forms around
a volcano’s central opening.
6. Label the picture: lava flow, vent,
crater, magma chamber, pipe
• 7. What are the two types of volcanic
eruptions?
• Quiet
• Explosive
• 8. What is silica?
• Material found in magma
• 9. A volcano erupts quietly if its magma is
__________ or _________________.
Directions: Which does the
following describe? Pahoehoe or aa
10. Looks like a solid mass of
ropelike coils
10. Pahoehoe
11. Rough surface of jagged lava
chunks
11. Aa
12. Forms from fast moving, hot lava
that is thin and runny
12. Pahoehoe
13. Cooler and thicker
13. Aa
Pahoehoe
Aa
14. A volcano erupts explosively if its magma
is high in silica. High-silica magma is
_________ and _____________.
15. Explain what happens during an
explosive eruption.
*Magma builds up in a volcano’s pipe,
plugging it.
*Dissolved gases, water vapor cannot
escape from the thick magma
*Trapped gases build up pressure
16. Contrast the silica content of magma in quiet
and explosive eruptions.
The magma of a quiet eruption is LOW in silica
The Magma of an explosive eruption is HIGH in
silica
Directions: Describe what the sizes are
during the explosive eruptions.
Volcanic Ash
Smallest pieces: fine, rocky particles that
are as small as a speck of dust
Cinders
Pebble sized particles
Bombs
Larger pieces: can range from the size of
a gold ball to the size of a car
18. How does an explosive
eruption produce pyroclastic flow?
Thick, sticky lava builds up in a
volcano’s pipe and plugs it. The
trapped gasses build up pressure
until they explode. The erupting
gases force the magma out with
great force which breaks the lava
into fragments that quickly cool and
harden in different sizes.
Directions:
Geologists often use the terms active, dormant,
or extinct to describe a volcano’s stage activity.
Define the terms below.
19. Active
Live volcano that is erupting or has shown signs
that it may erupt again in the future
20. Dormant
A volcano that is sleeping; scientists expect it to
awaken in the future and become active again
21. Extinct
A volcano that is dead, or unlikely to erupt again.
22. Name some warning signs that may signify a
volcanic eruption may happen.
*Tiltmeters: Detect the slight surface changes in
elevation and tilt caused by magna moving
underground
*Monitor gases escaping from a volcano
*Monitor small earthquakes that occur around a
volcano before an eruption
*Rising temperatures in underground water
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