To learn more about soils that occur in your area, this exercise will access the National Soil Survey Center Laboratory Research Database of soils throughout the United States.

1. Begin your search by entering the National Soil Characterization Database website.

2. Follow the link for "Access National Soil Characterization Data Online".

3. On the next page, "Select Research Data Here" and then "Area By State And County".

4. Select your state or other location from the links at the bottom of the page. Once at your state, use the drop-down menu to select your county. On a separate sheet of paper, list the types of soils described for your county.

5. If your county returns more than one soil type, select any two by placing a check mark in the box and click on the "Go to DB Engine" button. At the next page, choose the "Characterization" option from the menu, and click on "Submit Query".

6. Note the disclaimer on the next page, and click on "Continue to Seek Results".

7. When the results for each sample appear, compare the quantities of clay, silt, and sand in each sample.

a. Are they similar or do they differ dramatically?

b. What geological factors might account for the similarities and differences observed in your soil samples?

c. Do the proportions of clay, silt, and sand change in each soil horizon? What geological factors might account for this?

d. In general, is there a relationship between clay content of a soil and abundance of calcium (CA), magnesium (MG), sodium (NA), or potassium (K)?