BACKGROUND:
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.
PROCEDURE:
- 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.
- Review the characteristics of laterites, pedocal and
pedalfers from the Pre Lab.
- 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.
- 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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