Objectives:

• Learn to understand and interpret topographic profiles of the earth's surface.
• Practice the jigsaw cooperative learning strategy.

Some Definitions:

• topographic profile: a side view of the shape of the earth's surface.

Background. Topographic maps show the shape of the earth's surface and features on it, from a perspective looking down on the earth's surface from directly above. However, this isn't the only useful perspective of the shape of the earth's surface (that is, the earth's "topography"), that we can get. If you imagine slicing the earth open with a vast knife, and looking at the exposed slice from the side, you'd get an alternative perspective of the shape of the earth's surface. This perspective is called a topographic profile.

Pedagogical Strategy: A hands-on, jigsaw approach to help students visualize how contour lines represent topography on a map. Each student first becomes an "expert" on the profile of one particular landscape, then teaches other students about it.

1. Students form small groups. Each group has copies of a topographic map drawn for a clay model of a simple landscape built during a previous exercise ("Hands-on Jigsaw Activity: Topographic Contour Maps").
2. Students view Chapter 9, "Topographic Profiles", of the "Introduction to Topographic Maps" CD, together.
3. Students uses the topographic map of their particular landscape to draw a topographic profile lengthwise along that landscape, including the highest point(s) (and lowest points, if any), as described in the CD in step 2.
4. Students cut their clay model in half lengthwise along the same portion of the landscape as the profile they just drew, and compares the drawing with the sliced-open model.
5. Each student shows members of other groups how the topographic profile represents aspects of the modeled landscape, and relates those aspects to features on the topographic contour map of the landscape constructed in the earlier exercise.

Materials Needed:

• "Introduction to Topographic Maps" CD.
• Contour map of clay model landscape (drawn in an earlier exercise)
• Ruler with a centimeter scale.
• Template for drawing a topographic profile (handout).
• Clay model of a landscape (constructed in an earlier exercise).
• Knife (for cutting the model in half)

Detailed Instructions:

1. Choose one of the "landscapes" below, different from the one you constructed in an earlier exercise:
   
   
   1. a hill with one side much steeper (nearly a cliff) than the other sides
   2. a hill with two ridges extending down along its slopes with a valley in between
   3. two hills, with a dip or saddle between them about half as high as the lowest hill
   4. a hill next to a depression
      
      
2. The person who chooses landscape (a) above should get a topographic map of that landscape drawn by one of their permanent groupmates in an earlier exercise, then join their counterparts from three other permanent groups to form a temporary group. Those who chose landscapes (b), (c), and (d) will do the same, resulting in several temporary "landscape groups". Introduce yourself to your landscape group members, then check to make sure your group has got everything on the list of materials above.
   
   
3. View Chapter 9, "Topographic Profiles", of the "Introduction to Topographic Maps" CD. This describes a procedure for constructing a topographic profile, which you'll adapt.
   
   
4. Draw a line lengthwise through the topographic map of the landscape that you've chosen, passing through the highest point(s) of the model and, if possible, the lowest point(s), if any. (For landscape (b) above, is there a more interesting profile that you could construct? If so, do that one instead.) Following the procedure outline on the CD, use a ruler with a centimeter scale to draw a profile of the landscape on the topographic profile template provided to you.
   
   
5. Using a knife, slice your clay model in half lengthwise along the same line as in step (4) above. Compare your profile with the one revealed by the dissected landscape model.
   
   
   
6. When you have a completed profile, return to your original, permanent group. Then:
   
   1. take your group to visit your model;
   2. show the topographic profile that your landscape group drew; and
   3. identify for your group members the features of the profile that portray the various aspects of your model landscape, and how they relate to aspects of the contour maps constructed for that model in an earlier exercise.
      

References:

• United States Geologic Survey (USGS) Maps Booklet
  (http://erg.usgs.gov/isb/pubs/booklets/usgsmaps/usgsmaps.html)
  (A brief overview of the types of maps sold and distributed by the USGS)
  
• USGS National Mapping Information, "Topographic Map Symbols"
  (http://erg.usgs.gov/isb/pubs/booklets/symbols/)
  (Detailed explanations of topographic maps and the symbols on them, including sections entitled "What is a Topographic Map?", "Reading Topographic Maps", and "Topographic Map Information")