Goal: In this lesson you will create a map and examine the location and patterns of plate boundaries, earthquakes, and volcanoes in Africa and the world.
GIS Skills Involved: Map symbolization and spatial queries
Materials: To complete this lesson you will need ArcGIS software and the Africa Lesson data (Download the Data for Activities 4-7).
Step 1. Open ArcGIS and start with a new empty map. Using the Add Data tool , add the following shapefiles: Continent.shp, Plates.shp, Earthquakes.shp, and Volcanoes.shp.
Step 2.Make the Continent fill pattern transparent by opening up the Layer Properties dialog box. Double-click on the continent.shp layer and click on the "Symbology" tab. Click in the colored box and choose "Hollow". Click "Apply" close the Layer Properties box.
Step 3. Change the size and color of the Earthquakes symbol to green circles. Double-click on Earthquakes layer to bring up the Layer Properties, and click on the "Symbology" tab. Click on the dot symbol and change the size to 8 and choose a green color. Click "OK" and close the Layer Properties box.
Step 4. Now change the size and color for the Volcanoes and Plate Boundaries layers the same way you changed the Earthquakes. Make the Volcanoes layer red triangles and the Plate Boundaries layer a thick brown line.
Step 5. Arrange the layers in the View window so they are in the following order – Plate Boundaries, Volcanoes, Earthquake, Continents. To do this, simply click on the layer and drag it up or down while holding the mouse down.
Step 6. Answer the following questions using this map setup.
A) Where are the majority of the earthquakes in the world located in relationship to the plate boundaries? Why?
B) Zoom in on Africa. Where are most of the earthquakes in Africa located in relationship to the plate boundaries?
C) A rift zone is where a continent is believed to be spreading apart, but not on a plate boundary. A rift zone causes magma to rise to the surface and erupt in a line of volcanoes. Based on this information, in what African countries is the rift zone located (to see the country name click on the Identify tool and then click on the country)?
Step 7. Zoom back out to the full extent of the map using the Full Extent tool . Now let’s open the attribute table and sort by a particular field. Right-click on the Earthquake layer and select "Open Attribute Table". Click on the column titled "Magnitude" to select the entire field, right click and choose "Sort Descending". Now the earthquakes are displayed according to magnitude, from largest to smallest. Click on the first field, which should be the largest magnitude earthquake (9.3). The corresponding point should be highlighted in blue on the map (you may need to zoom in and out to find the point).
D) When, and on which continent, did the largest magnitude earthquake occur (you might need to turn the continent labels on)?
Step 8. Now let’s figure out which volcano in Africa has the highest elevation by performing a spatial query. At the top of the screen click "Selection" —> "Select by Attributes". Choose "Volcanoes" as your layer, and "Create New Selection" as your method. Double click "Elevation" from the list and click the "greater than" sign. Let’s begin by entering 2000 as our elevation criteria. Click "OK" when done. All the volcanoes in the world with an elevation greater than 2000 should now be selected on your map. You will notice there are several volcanoes in Africa that meet this criteria. Go back and enter 3000, then 4000. Keep entering new values until only one volcano in Africa remains selected.
E) What is the name and elevation of the tallest volcano in Africa and where is it located?
Save your map and exit ArcGIS.
*** End of Africa Activity 4 for ArcGIS ***
Return to main page for Exploring Africa's Physical and Cultural Geography Using GIS