Name _____________________ Pd____________
Date _____________________________________
Chemistry of Magma - Does It Tell Us Anything About How a Volcano
Burps?
Indicator: 2.6.C.2.a. Recognize and describe the evidence for plate movement and the global
patterns of earthquakes and volcanoes.
Overview: Geochemists study the chemical composition of magma to predict patterns of
volcanic eruptions as well as to understand the composition of the Earth's interior. You
will use the chemical composition of the magma to distinguish between the different
types of volcanic rocks. The chemical data will be used to locate on a world map the
different types of volcanoes based on their rock type. You will then use this data to
predict where the most violent eruptions will occur. The Data Sheet includes the latitude
and longitude of selected active volcanoes around the world and the chemical
composition of rocks from each. The chemical composition includes silica dioxide
(SiO2) and iron oxide (Fe2O3).
Directions:
1.
The Volcano Data Sheet shows that rocks from volcanoes are classified
into three different rock types – rhyolite, andesite, and basalt. A scatter plot of the
data from the Volcano Data Sheet is attached. Use the Summary of Magma
Composition Table to help you determine the range of SiO2 for each rock type. Then
draw horizontal lines to separate the data points on the scatter plot into the three
groups of rocks. Complete the following chart based on this information.
Percentage (%) Range of SiO2 in Magma
Rock Type
rhyolite
andesite
basalt
Range (%)
-
2. Use the table above to identify on the Volcano Data Sheet the rock type of other
volcanoes. Base your identifications on SiO2 composition of the volcano’s magma.
3. Using the latitude and longitude coordinates on the Data Sheet plot all the volcanoes
using a small triangle () on the World Grid Map. Use a different colored pencil for
the rock type associated with each volcano as follows:
Andesite
Rhyolite
Basalt
red
blue
green
Follow-up Questions:
1. Look at the Plate Tectonics Map on page 83 in the textbook. Describe the general
relationship between the location and type of volcanoes plotted and the type of
tectonic plate boundary (convergent, divergent or transform).
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2. What happens to the percentage of silicon dioxide (SiO2) as the percentage of iron
oxide (Fe2O3) in volcanic rocks increases? Refer to the Data Sheet to determine the
correlation.
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3. Silicon dioxide (SiO2) in magma is one factor that controls the violence of volcanic
eruptions. Magma from the most violent eruptions has a higher percentage of
silica compared to quiet eruptions. Use the Data Sheet to complete the chart below.
Look at the rock samples provided to determine the color of the rock. Label the type
of eruption as either violent, quiet to violent or quiet based on percent of SiO2.
Type of Rock
Color of Rock
Relative % of SiO2
Most
Intermediate
Least
Type of Eruption
BCR PROMPT: You are to present a recommendation to the UN Committee on Natural Disasters. This recommendation will be used to warn
citizens in regions that have the most potential for violent volcanic eruptions. In this recommendation, be sure to include at least the following:

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
Regions of the world that would experience the most violent eruptions.
The reasons why these regions have violent eruptions.
Other factors should the UN committee consider other than composition of magma.
CLAIM/TOPIC SENTENCE:
DETAIL 1: Region of the world that would
experience the most violent eruption:
CONCLUDING SENTENCE:
DETAIL 2: Evidence from activity to support
this choice of violent eruptions:
DETAIL 3: Evidence to support this location
other than the magma composition:
Final Copy: Use the graphic organizer above to organize your response. Write your
final draft below.
BCR
You are to present a recommendation to the UN Committee on Natural Disasters. This
recommendation will be used to warn citizens in regions that have the most potential for
violent volcanic eruptions.
In this recommendation, be sure to include at least the following:



Regions of the world that would experience the most violent eruptions.
The reasons why these regions have violent eruptions.
Other factors should the UN committee consider other than composition of
magma.
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DATA SHEET
Volcano Location
Pacific U.S.
1. Lassen, CA
2. Crater Lake, OR
3. Mt. Rainier, WA
4. Mt. Baker, WA
U.S. Interior
5. Yellowstone Park, WY
6. Craters of the Moon, ID
7. San Francisco Peaks, AZ
Central America/West Indies
8. Paricutin, Mexico
9. Popocatepetl, Mexico
10. Mt. Pelee, Martinique
11. Santa Maria, Guatemala
12. Mt. Misery, St. Kitts
South America
13. Cotopaxi, Ecuador
14. Misti, Peru
Alaska and Aleutian Islands
15. Katami, Alaska
16. Adak, Aleutians
17. Umnak Island, Aleutians
18. Kamchatka, Russia
Japan
19. Mt. Fuji, Honshu
20. Izu-Hakone, Honshu
East Indies
21. Mayon, Philippines
22. Krakatoa, Java & Sumatra
23. Karkar, New Guinea
Central Pacific
24. Mauna Loa, Hawaii
25. Galapagos Islands
26. Mariana Islands
South Pacific
27. Aukland, New Zealand
28. Tahiti
29. Samoa
North Atlantic
30. Surtsey, Iceland
31. Mid-Ocean Ridge
Africa
32. Kilimanjaro, Tanzania
Latitude
Longitude
% of Magma Composition
SiO2
Al2O3 FeO + Fe2O3
40N
43N
47N
49N
121W
122W
122W
122W
57.3
55.1
62.2
57.4
18.3
18.0
17.1
16.6
6.2
7.1
5.1
8.1
45N
43N
35N
111W
114W
112W
75.5
53.5
61.2
13.3
14.0
17.0
1.9
15.2
5.7
19N
19N
15N
15N
17N
102W
98W
61W
92W
63W
55.1
62.5
65.0
59.4
59.8
19.0
16.6
17.8
19.9
18.3
7.3
4.9
4.5
5.9
7.3
1S
16S
78W
71W
56.2
60.1
15.3
19.0
9.7
5.0
58N
52N
53N
57N
155W
177W
169W
160E
76.9
60.0
52.5
60.6
12.2
17.0
15.1
16.4
1.4
6.9
12.8
7.9
35N
35N
139E
139E
49.8
53.8
20.6
14.8
11.2
13.0
13N
6S
5S
124E
105E
176E
53.1
67.3
60.1
20.0
15.6
16.4
8.2
4.3
9.6
19N
1S
16N
156W
91W
145E
49.6
48.4
51.2
13.2
15.4
17.3
11.9
11.8
10.9
38S
18S
13S
176E
149W
172W
49.3
44.3
48.4
15.6
14.3
13.3
11.9
12.4
12.3
63N
60N
20W
30W
50.8
48.2
13.6
16.5
12.5
11.7
3S
37E
45.6
10.3
12.6
Rock Type
Summary of Magma Composition
Volcano
Krakatoa
Lassen
Mt. Rainier
Craters of the Moon
Paricutin
Mt. Pelee
Izu-Hakone
Umnak Island
Cotopaxi
Mayon
Galapagos
Aukland
Samoa
Surtsey
% of SiO2 in
Magma
67.3
57.3
62.2
53.5
55.1
65.0
53.8
52.5
56.2
53.1
48.4
49.3
48.4
50.8
Rock Type
Rhyolite
Andesite
Andesite
Andesite
Andesite
Andesite
Andesite
Andesite
Andesite
Andesite
Basalt
Basalt
Basalt
Basalt
Percent SiO2
SiO2 Composition of Volcanoes
80
75
70
65
60
55
50
45
40
SiO2 Composition
0
10
20
Location Num ber
30
40