VOLCANOES AND VOLCANIC ACTIVITY
Geomorphology of Volcanoes
In this exercise, you will compare the geomorphology of composite volcanoes (stratovolcanoes)
and shield volcanoes using Google Earth.
Fig. 1.
Google Earth image of Mount Fuji, Japan.
In order to compare some geomorphic attributes of composite and shield volcanoes, it will be
necessary to construct topographic profiles across a number of examples worldwide. To do this,
you will use the ‘Measure’ tool in Google Earth and enter data into a Microsoft Excel
spreadsheet.
1. To construct a topographic profile, begin by enabling the metric measures in Google
Earth. This is accomplished by clicking on ‘Tools’ on the menu bar at the top of the page,
then clicking on ‘Options’. When the ‘Options’ dialogue opens, you will see in the lower
left of the dialogue an ‘Elevation’ option. Choose Meters, Kilometers, then ‘Apply
Settings’.
2. Next, you should start up the Microsoft Excel program as you will be entering data
generated from Google Earth into this spreadsheet. When the spreadsheet opens, label
one column ‘Distance (m)’ and one column ‘Elevation (m)’.
3. Now, return to the Google Earth window and enable the ‘Measure’ tool by clicking on
the word ‘Measure’ (or simultaneously using ‘ctrl + 6’ keys on your keyboard). When the
‘Measure’ dialogue box appears, use the drop down window to choose meters as the units
of distance. Also select the tab labeled ‘Path’.
4. Note that the ‘Measure’ icon on your image appears as a box with tick marks along the
mid-points. This box can be used to add points along your profile with approximately
equal spacing; simply click the first point, then move the box until one of its tick marks is
aligned with this point; now click again. The next point is located approximately the
distance from the center of the box to a tick mark. This distance varies depending on the
level to which you are zoomed into the image. In addition, from point to point, the
distance is not precisely the same, but it is close enough for the exercises we are
attempting to conduct. If you add a point and want to delete it, simply right click on your
mouse and it will disappear.
5. You can determine the approximate spacing to each point by noting the cumulative
distance along your profile and entering this distance at each point into the spreadsheet.
6. To begin your topographic profile, go to the first entry in the table below and enter the
coordinates of the volcano in the Google Earth query bar. When Google Earth relocates
to this position, zoom out until you can see the entire volcanic edifice.
7. Select a point along one edge of the volcanic edifice as your starting point and click on
the ‘Measure’ tool. Note the distance reads ‘0.00’ meters. Type this value into the
‘Distance’ column of your spreadsheet. Note the elevation of this point by placing the
‘Measure’ cursor over it. A pointing finger icon will appear and you will be able to read
the elevation (“elev”) of the point along the bottom of the image window to the right of
the longitude.
8. Increment to your next point along your traverse by moving the ‘Measure’ cursor
approximately by the half-width of the cursor box, then click again. This is your second
profile point. When you click this point, note the distance along your profile (read from
the ‘Measure’ dialogue box) and the elevation of the point (read along the bottom of the
image to the right of the longitude). Enter the distance and the elevation into their
respective columns in your spreadsheet. Repeat this process until you have completed a
traverse across the volcanic edifice displayed on Google Earth.
9. To plot this topographic profile in Excel, choose the ‘Chart’ function from the ‘Insert’
menu at the top of the screen.
10. For ‘Chart Type’, choose, ‘XY (Scatter)’. Choose the scatter plot option ‘Scatter with
data points connected by lines’. Make the ‘DISTANCE’ column the X-axis and
‘ELEVATION’ column the Y-Axis of your plot.
11. To add a second topographic profile to the first from the ‘Chart’ dialogue box, click on
the ‘Series’ tab at the top of the box. In the ‘Series’ box in the lower left corner, click on
the ‘Add’ button. Type ‘Mount Fuji’ in the ‘Name’ box to the right, then for ‘X values’
add the data from the ‘DISTANCE’ column from Mt. Fuji; ‘Y values’ will be the
‘ELEVATION’ data from Mt. Fuji.
Mauna Kea
DIST (m) ELEV
(m)
0
994
1778.66
1095
3671.09
1234
5450.44
1387
7318.48
1523
9200.09
1733
10957.04
1906
12713.07
2121
14474.97
2426
16213.23
2708
18930.71
2972
20632.98
3247
21311.45
3456
22974.38
3626
24726.15
3896
26460.38
4025
28099.71
3874
29753.04
3654
31523.05
3377
33183.97
3097
34866.75
2772
36568.32
2465
38280.48
2258
40004.78
2034
41732.84
1867
43574.11
1690
45320.51
1538
47073.87
1396
48832.48
1267
50599.34
1139
53373.37
1015
54188.03
892
56049.62
764
57859.27
618
59669.37
491
61497.33
347
Fuji
DIST (m) ELEV
(m)
0
896
603.98
962
1207.78
1033
1811.43
1112
2414.16
1202
3023.2
1322
3651.22
1425
4236.8
1520
4824.15
1639
5453.65
1823
6062.65
2102
6685.37
2382
7270.37
2724
7831.75
3051
8404.84
3404
8917.6
3653
9401.48
3648
9881.71
3451
10375.16
3166
10885.23
2907
11410.46
2661
11947.53
2448
12530.11
2227
13120.11
2048
13718.98
1883
14291.64
1741
14905.95
1596
15492.29
1468
16077.28
1369
16670.43
1264
17258.23
1190
17885.13
1113
18517.42
1035
19149.85
970
19748.77
912
20344.62
866
4500
TOPOGRAPHIC PROFILES
4000
Mauna Kea
Mount Fuji
3500
ELEVATION (m)
3000
2500
2000
1500
1000
500
0
0
10000
20000
30000
40000
50000
60000
70000
DISTANCE (m)
12. Describe what you observe on the resulting topographic profile for these volcanoes.
Both volcanoes are similar heights, though Mauna Kea is much broader, implying more
gentle slopes.
13. Note that both profiles are nearly triangular above 1000 m elevation. Given that each
volcano is nearly circular, each is actually cone-shaped. Use the Internet to locate the
formula for the volume of a cone.
14. Once you have located the formula for the volume of a cone, calculate the volumes of
Mauna Kea and Mt. Fuji above from the 1,000 m elevation to each volcano’s summit.
How do these volcanoes compare?
Mauna Kea = ca. 2.82 x 1012 m3; Fuji = 3.07 x 1011m3; the volume of Mauna Kea is
approximately 1 order of magnitude (10 times) greater than Mt. Fuji.
15. OPTIONAL: Read the Wikipedia article on Mauna Kea. Note that the volcano rises over
5,000 m from the floor of the Pacific Ocean. Assuming the volcano maintains its coneshaped form to the seafloor, recalculate its volume from the seafloor base to the summit.
5.60 x 1013m3
Table 1. Location of shield volcano and composite volcano for this exercise.
NAME
LATITUDE
LONGITUDE
Mauna Kea, Hawai’i
19.815332
-155.472645
Mount Fuji, Japan
35.366673
138.733347
LINKS TO RELATED SITES:
Wikipedia entry on shield volcanoes: http://en.wikipedia.org/wiki/Shield_volcano
Wikipedia entry on composite volcanoes: http://en.wikipedia.org/wiki/Composite_volcano
Wikipedia entry on Mauna Kea: http://en.wikipedia.org/wiki/Mauna_Kea
Wikipedia entry on Mt. Fuji: http://en.wikipedia.org/wiki/Mount_Fuji