Universe Cycle - Geography (4)

  • Classifying soil.
  • Plotting data of soil locations.
  • laterite
  • pedalfer
  • pedocal
  • soil

Students look at soil types and plot their locations on a map.

Soil from North Carolina


Maps present us with information about subjects ranging from soil composition to population. Sometimes simplified maps do not fully explain the information they present. However, a simplified map is easier to understand, and conveys accurate general patterns. Detailed maps may contain comprehensive information, but may be harder to interpret. In this lab students will first look at a generalized soil map and then plot data for a detailed area. The lab is based on the San Francisco Bay area, but any location could be used, if soil samples are available.

If you want to customize this lab, you would need to get a map of the local area and then collect soil from different locations.  Remember this is a mapping exercise and plotting soil data is just for students to get a sense of how scientists use maps. 

  1. You may want to show students different types of maps that are included in your module. Ask them if more detailed maps have more detailed information. They should answer yes. Ask them what happens when you want to generalize or make a simple map; ask them if this causes a loss of information. Again, they should answer yes. You may want to introduce the two maps used in the lab, and demonstrate how the San Francisco area map is a detailed version of the United States map.

    We highly suggest you customize this lab to your local area. Replace the maps appropriately.

  2. Review the characteristics of laterites, pedocal and pedalfers from the Pre Lab.
  3. In Exercise 1, the students examine a generalized map of the United States. They should conclude that there are mainly pedocals in the west and pedalfers in the east. In Exercise 2, the students first examine 10 bags of soil from the San Francisco Bay area to determine whether they are pedalfers or pedocals. To help them decide, emphasize that pedalfers are dark and pedocals are lighter color (sometimes grayish). The students may have difficulty classifying some samples, depending on how they visualize light and dark. Remind them that the point of the lab is for them to learn about plotting information on maps, and finding patterns from the information.  Scientists many times have to make a decision whether it is dark, light, or red.   So there is really no right or wrong answer.  You may want the students to compare their maps with a neighbor and if they conflict to look at the sample again and maybe make another decision.  Scientist argue and discuss their conclusion all the time!

    The students will next plot each soil by composition on the San Francisco Bay area map. You may wish to have them to describe the soil on the lab sheet. The students do not have to take the soil out of the bag. You might want to have magnifying glasses available so they can record "other" objects in the soil. These answers are somewhat subjective. The key objective for this activity, is to plot and interpret data.

  4. After the students plot the information on the map, discuss why the map of the San Francisco Bay area has pedocal and pedalfer soil. According to the general map of the United States there should only be pedocals. The answer is that the larger map cannot show detail, only the soil type that is most abundant. Hopefully, the students will see that there are more pedocals than pedalfers on the detailed map. This indicates the general map is basically accurate, but not precise.

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