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Chapter 7 Volcanoes – Test Review
Answer each of the following questions with the BEST possible answer.
1. What is the Ring of Fire?
2. Why does the Ring of Fire exist?
3. Compare and contrast hot spot volcanic islands and island arcs. Give examples of each.
4. Explain if and how volcanoes can form at divergent plate boundaries.
5. Explain if and how volcanoes can form a convergent plate boundaries.
6. List the 3 types of volcanoes, important/defining characteristics of each, sketch a picture, and give
an example of one found on Earth.
Volcano Type
Characteristics/how it
forms (include
viscosity of lava)
Picture
Example/Name One
Eruption
Type(s)
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7. Complete the chart.
Silica
Amount
Viscosity
Temperature
Color
Speed of
Movement
Name of
Lava
Type of
Eruption
8. Explain how a pyroclastic flow can be a more deadly hazard than a lava flow.
9. What hazard must you be aware of when a quiet eruption occurs? (Like on the Hawaiian islands?)
10. What is most likely the cause of volcanic activity on the island of Iceland?
11. Silica often becomes trapped in magma. What kind of eruption do you
think Magma A will most likely cause?
12. Summarize what occurs when a volcano erupts. (Hint: Section 7.3)
13. What geothermal evidence can be found in areas of current or past volcanic activity?
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14. Fill in the following chart relating to landforms and the volcanic material that makes it.
Landform
Name
Description of how it
formed
Sketch
Composed from
Lava or
Magma?
Dome
Mountains
Lava
Caldera
Large body of magma cools
inside the crust. Becomes
visible above ground through
erosion of the ground above
the batholiths or through uplift.
Magma
Shield Cone
Volcano
High viscosity, high silica, low
temperature lava builds up
ash, cinders, and bombs
around vent as volcano erupts
explosively.
Magma forces itself across
rock layers vertically
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15. The following hypothesis was made and the following data was collected while completing a lab
similar to the one done in class exploring viscosity, silica content and explosiveness.
Hypothesis:
Low viscosity lava will have high silica amounts and will result in the most explosive eruption
because the lava will be able to move easily and will be ejected from a volcano very easily.
TABLE 1.
Composition
Distance Traveled
(cm)
Time (sec)
Rate of Flow (cm/s)
10
120
0.08
30
120
0.25
20
120
0.17
Viscosity
TABLE 2.
Composition
Amount of Lava in
volcano before
eruption
Amount of Lava
in volcano after
eruption
Amount of
erupted from
volcano
Type of
Eruption
Height of
Eruption
1000 mL
600 mL
400 mL
40 cm
1000 mL
400 mL
600 mL
60 cm
1000mL
200mL
800 mL
80 cm
a. Fill in the missing data in Table 1 and 2 based upon the results.
once. Use the terms below:
High Silica
Medium Silica
Medium Viscosity
High Viscosity
Explosive
Medium Eruption
Terms may be used more than
Low Silica
Low Viscosity
Quiet
b. Consider both data tables above and the hypothesis that was made. Accept or reject the
hypothesis and explain why you did so USING and CITING EVIDENCE from the lab results.
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16. Read the article and answer the questions that follow.
Volcanic blast, not giant bear claws, formed Wyoming's Devils Tower
By Scientific American, adapted by Newsela staff on 03.19.15
Native Americans believe that giant bears made long scratch marks in
Devils Tower as they attempted to climb to the top. But the vertical lines
along the sides of the almost 390-meter-tall (nearly 1,300 feet) rock
formation in Wyoming are not claw marks. They are actually the edges of
columns of igneous — volcanic — rock. The column formed as the
molten rock cooled and contracted, cracking apart.
Czech Scientists Check It Out
But how did the columns of Devils Tower form — below the ground or as part of a violent volcanic eruption?
Scientists have suggested many theories over the years. The most popular today hold that Devils Tower
was born 49 million years ago as a rising half dome of magma, molten rock. The magma was squeezed to
the surface either between underground layers of rock or deep inside a volcano. Prokop Závada, a
geologist at The Czech Academy of Sciences, and three other researchers became interested in the
mystery of Devils Tower. They found a clue in another butte in the Czech Republic, called Boren. A butte is
an isolated hill with steep sides and a flat top. Boren is similar to Devils Tower, although it is more rounded
and covered with trees.
Maar-Diatreme? It's A Blast!
The researchers concluded that Boren was
created by a sudden type of volcano called a
maar-diatreme. This kind of volcano blasts a
crater on the Earth's surface when molten rock
underground meets groundwater. After the
blast, the researchers think, a flat dome of lava
filled the crater, acting like a plug. Wind and rain
eroded away at the edges of that dome until
only the innermost portion remained. We call
that isolated core Devils Tower. Because Devils
Tower is so similar to Boren, the Czech team
decided to see it was formed in the same way.
The researchers looked at two main
characteristics of Devils Tower. They studied
the shape of its distinctive columns and the
position of magnetic minerals within them. The
National Park Service let the researchers collect one new rock sample from Devils Tower in order to
analyze its magnetic properties. The researchers discovered that near the base of Devils Tower, tiny
needle-shaped minerals within the rock are oriented close to vertical. That is the direction the lava flowed
before it hardened. Closer to the top, the minerals turn horizontal.
Plaster And Computer Models
Based on that information, the researchers made digital and physical models. For the physical model, they
mixed some magnetic particles in with soft plaster. They squeezed the material upward through an upsidedown cone full of earth and rock until it formed a mound on the surface. This resembled the eruption of lava
following a maar-diatreme volcano.
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When the plaster hardened, the researchers cut the
cone open to examine the inside. They measured
which way the magnetic particles pointed just as
they had done at Devils Tower. They also made a
computer simulation of cooling volcanic rock. The
simulation let the researchers compare columns
created as Devils Tower cooled under different
conditions. The columns of Devils Tower matched
the expected pattern exactly. In the plaster models,
the direction of the magnetic particles also matched
the direction of the minerals from Devils Tower.
They were closer to vertical around the base and
horizontal near the top. In a paper, Závada and his
team concluded that Devils Tower was caused by an
underground volcano like Boren in the Czech
Republic.
This Bears Further Study
Western Washington University’s Bernard Housen was not involved in the study. He said the work was
“interesting and certainly very plausible” or believable. However, he was not convinced it ruled out other
possible explanations. The problem is that there isn’t much data from Devils Tower itself, since the
government has allowed so few samples to be taken. “So, it is likely that the origin of Devils Tower will
remain uncertain," he said. This is in part because the government wants to make sure that the butte is
preserved, Housen said. It might be possible to study the similar, if less spectacular, buttes near Devils
Tower, however. They were likely formed in the same way — with or without the help of giant bears.
Hint: When answering the following quote the article for evidence, use titles or sub-headings, or reference
paragraphs.
a. What is the main idea of this piece of text? What evidence from the article supports your
answer?
b. What is your opinion about the information in this text? What evidence from the article do you have to
support your opinion?
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