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Interpreting Topographic Maps and Aerial Photographs


Grades: Upper elementary through university.

Examine a USGS topographic map and an aerial photograph of the area of your corn maze. Download free digital topographic maps by going to the USGS Store and clicking on "Map Locator". Download free aerial photographs through Earth Explorer.

Discuss: What forces shape the landscape near the cornfield? What are the dominant natural hazards in this area? In which direction does this area drain? Into what river(s) does this area drain? Into what ocean do the rivers empty?

You could examine USGS topographic maps or a USGS national map of river systems to aid you. Maps of the river systems for each state can be downloaded from the National Map.

Trace the path of rain falling on this field to the ocean, including all rivers along the way. What is the river distance from this field to the ocean?

What is the elevation of your cornfield? Would you characterize the terrain of your field as flat, moderate, or steep? What do you think is the maximum slope on which a cornfield can be planted? What constraints operate on the slope of a cornfield? Compare the terrain constraints for corn to other crops. What other crops are grown in this area? Why? What percentage of the county you are in would you estimate as being cultivated for corn? The U.S. Department of Agriculture also has corn production maps.

From the aerial photograph, what would you say is the dominant land use in your cornfield's region? Why? Compare this land use to the land use based on an aerial photograph around your school. What are the differences? Why?

Compare the cornfield's elevation to the elevation based on a topographic map of your school. Is the cornfield higher or lower in elevation of your school? Why? What landforms are present? How have humans modified the landscape in cultivating corn and other crops?