Goal: In this lesson you will examine the locations of earthquakes that have caused tsunami effects in Africa and the effects these tsunamis have had on the country.
GIS Skills Involved: Map symbolization and measuring distances on a map.
Materials: To complete this lesson you will need ArcView software and the Africa Lesson data (Download the Data for Activities 4-7).
Step 1.Let’s make a map in ArcView showing tsunamis in Africa. Open ArcView and click "OK" in the pop up window (this will create a new project with a new view). The next screen will ask if you would like to add data to the view. Click "Yes" and add the following shapefiles (navigate to the folder where you saved the Africa Lesson data and hold down the shift key to add more than one shapefile at a time): country.shp, cities.shp, t_source.shp, and t_effect.shp. Put a check mark next to each one to make them visible.
Step 2. Now let’s rename the themes. Make the theme active by clicking on its name (i.e., its name appears raised). From the Theme pulldown menu choose "Properties" and change the name. Do this for all themes:
Step 3. Display the Cities theme as a Graduated Symbol. Double-click on the Cities theme to bring up the Legend Editor. Select "Graduated Symbol" as the Legend Type, and select "Population" for the Classification Field. Change the color of the circles to a dark purple and click "Apply" in the Legend Editor.
Step 4. Display the Tsunami Effects as bright blue stars. Double-click on the Tsunami Effects theme to bring up the Legend Editor. Click on the current symbol and then click on the thumbtack icon to bring up the Marker Palette . Find the star symbol (there are two stars--select the star that is filled with green), change the size to 14, and change the color to bright blue (using the paintbrush).
Step 5. Next, make the Countries theme transparent and the Tsunami Sources theme red. Open the Legend Editor for the Countries, select the paint bucket icon and select the upper left (white) box. Click Apply. For the Tsunami Sources theme, access the Marker symbol and change the size to 8 and the color to red.
Step 6.Arrange the themes in your view window in the following order - Tsunami Sources, Tsunami Effects, Cities, and Countries.
A) Use the Identify tool and find the two cities with a population greater than 2 million that you believe to be most at risk from a tsunami in Africa.
B) Why do you believe these two cities are the most at risk?
C) Open both the Tsunami Effects attribute table and the Tsunami Sources attribute table (right click on each —> Open Attribute Table). Arrange the two tables next to each other so that you can compare the dates. By comparing the date columns, determine which Tsunami Sources caused Tsunami Effects in more than one location. Leave the tables open for the next question.
D) When an earthquake causes a disturbance in a lake rather than in the ocean it is called a "seiche". Determine the date and name of the city and country where the Tsunami Effect was a seiche rather than a tsunami.
Step 7. Now let's use the Measure tool to determine the distance between the 2 tsunamis on the northwest coast of Africa. To do this, click on the Measure tool on the tool bar. Click once on a starting point and double click on the ending point. The distance will be displayed in the lower left hand corner of the screen. The distance should be approximately 515 km (see image below).
E) Zoom out so you can see the entire continent of Africa. Examine the tsunami source in the Atlantic Ocean northwest of the coast of Morocco. What year did it occur? How far did the tsunami travel from its source to where it hit the shore? Hints – use the Identify tool and Measure tool.
Step 8. Print a copy of your map layout.
Save your project and exit ArcView.
*** End of Africa Activity 6 for ArcView ***
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