Part 3—Investigate Volcanoes and their Distribution

Step 1 – Launch My World and Setup the Project

1. Launch My World (if necessary).
2. Make sure you are in Construct mode.
3. Select Geology from the Data Library pull-down menu.
4. Click and drag the following layers to your Layer List:
   
   • Volcanoes
   • *Plate Boundary Types
   • *Continents
5. * If you are continuing with the same project that you used in Part 2, you only need to add the volcanoes layer and you will need to turn off the Sea-floor age, Lines of Latitude & Longitude, and Plate Boundaries layers.
6. Switch to Visualize mode by clicking the Visualize tab.
   
   
   

Step 2 – Examine the Contents of the Volcanoes Layer

1. Begin by examining the contents of the Volcanoes layer table.
Show Table Tips
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1. Table Tips: You can open an activated layer's table using the pull-down menu Layer > Show Layer Table... or selecting the Show Table of Selected Layer button .
2. Sort a field by clicking on the field name. Each click will sort the field, ascending , descending , and then back to unsorted.
Show me the Table of the Layer
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• How many volcanoes are listed in the Table of the Layer?
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1535 volcanoes are listed. The number is located in the upper left-hand corner of the table.
Histograms are a useful tool when reviewing the information contained in a layer table. A histogram allows you to display the distribution of values for each table attribute or field.
2. Create a Histogram / Bar Chart for volcano elevation.
Show me how
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1. With the Volcanoes layer active, click the Show Histogram for the Selected Layer button .
2. Use the pull-down menu to select elevation. Change the minimum value to "0" and click Enter.
• What is the maximum value for volcano elevations using the statistics at the bottom of the window?
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6,887 ft.
• What is the average (mean) elevation for all volcanoes worldwide?
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1,748.55 ft.


3. Change View Histogram for Field to Primary Type.
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Classify the Volcano layer by choosing "Primary Type" from the pull-down menu.




• Which volcano type is the most frequent worldwide?
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The stratovolcano is the most common. All of the other types of volcanoes are at about the same level, never exceeding 240 volcanoes. However there are over 700 different stratovolcanoes around the world.

4. Close the Histogram / Bar Chart window.

Step 3 – Explore the Data between Types of Volcanoes and their Locations on the Continents

1. From the data in the table you can observe the frequency of Volcano types, next you will examine them on the map.
• What observations can you make about volcano locations compared to the continents?
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Volcanoes are usually located on the coasts of continents, along the plate boundaries.
• What visual pattern do you notice in volcano locations?
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The volcanoes are patterned according to the plate boundaries for the most part. Others are scattered across the continents.
• Provide a possible reason why volcanoes occur in these locations.
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When plate boundaries crash into each other, they form mountains and volcanoes. This is also why there is magma under the volcanoes.
2. Use Analyze mode to create specific selections of the location of Stratovolcanoes and Shield volcanoes using the Select by Value feature.
Show me how
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1. Select items from Volcanoes whose Primary Type matches one of the values checked below: choose Stratovolcano. Provide a result name that will describe the selection.
2. Return to Analyze mode and create a second section from Volcanoes whose Primary Type matches one of the values checked below: choose Shield Volcano. Provide a result name that will describe the selection.
3. Switch between the different selections and make observations of where Stratovolcanos and Shield volcanos are located.
Highlight Mode Tip: After making a selection in Analyze mode, try different Highlight Modes to see different ways to display your selection.

3. Is there a general difference in the location of Strato vs. Shield volcanoes worldwide?
Show me how
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1. Turn on the Plate Boundary Types layer and observe the relationship between plate boundaries and volcano types.
2. Change the legend of the Plate Boundary Types layer to "Margin Type."
Show me the answer
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The general location of the two volcanoes types is the same. Besides the fact that there are more stratovolcanoes, the only other difference is that the shield volcanoes are a little more dispersed and scattered, but not by much.

Step 4 – Observe the Relationship between Volcanoes and Plate Boundaries

1. With the Volcanoes and Plate Boundaries layers on, consider the following questions:
   • What is the pattern of volcano type at divergent vs. convergent boundaries?
   Show me the answer
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   Along the convergent boundaries, all different kinds of volcanoes are formed. Along the divergent boundaries, there are different kinds of volcanoes as well, but they are submarine volcanoes for the most part.
   • Does one type of volcano occur more often at a plate boundary than another?
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   There are more submarine volcanoes along the divergent boundaries versus the others. Also, volcanic fields appear to mainly be near the convergent boundaries.
   • Is the pattern of volcanoes similar on both sides of the plate boundary? Explain the pattern you observe.
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   Along the plate boundaries, the side with land has the bulk of the volcanoes. The side in the oceans have mostly submarine volcanoes and some shield volcanoes.
   • Summary question: For each boundary type, list evidence you've discovered that describes plate movement.
   Show me a hint
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   Hint: Volcanoes occur at Plate Boundaries, which types of boundaries do they most frequently occur around?