Materials

• Information on the area of each continent
• Various map projections

Instructional Activities

1. Ask students if they know why the changes identified on the maps during the previous session occurred. Base a class discussion on their responses. Ask students if they know of changes that have occurred in a country’s borders so recently that they have not yet appeared in textbooks.
   
   
2. Explain that it is not possible to take a round object and flatten its surface out without distorting something. Demonstrate this with an orange peel, a tennis ball, or a baseball. Projections are mathematically derived to move a portion or all of the Earth’s curved surface to a flat map. The goal of a good projection is to eliminate this distortion as much as possible. Different map projections reflect the Earth’s surface differently. Some reflect the size of continents more accurately, while others provide better information for navigational purposes. Display a map of the world, and ask students which continents are bigger. Then provide students with the actual size of each continent, or display a globe for comparison of continent sizes. Display a map that reflects each of the following aspects of the Earth’s surface displayed on different map projections:
   • Shape
   • Area
   • Distance
   • Direction
   NOTE: A mnemonic device to help students remember is “SADD.” Instruct students to compare the size and shape of Greenland with that of South America, using different map projections.
   
   
3. Demonstrate the following map projections, and explain how each one is used:
   • Mercator — ship navigation
   • Polar — plane navigation
   • Robinson — data representation
   Encourage students to speculate about why different projections may be used for different purposes
   
   
4. Assign a teacher-selected reading, worksheet, or other reinforcement activity, using available teacher resources.