Soils Profiles

By Derek Geise

Background Information:

Scientists use soil profiles to determine past climates and environments of deposition. Soil profiles can tell us if there was a river present in earlier times, the amount of plant growth determined by organic matter content, or whether wind and dust was the main soil builder. 

Purpose:

This lab will expose you to the method soil scientists use to gather data about past soil conditions. 

Materials:

Clear plastic or glass container. Food jars work well as well as clear plastic fruit containers. Samples of sand, gravel, black soil, and silt. 

Procedure:

  1. Obtain a clear plastic container. Place 1-2 cm of gravel in the bottom of the container.
  2. Next place about 3-4 cm of black soil on top of the gravel.
  3. Next place 1-2 cm of sand on top of the black soil
  4. Finally place 5 cm of silt on top of the sand.
  5. Have students draw out the soil sample on a piece of paper. Use colored pencils to color the drawn samples. Make sure the samples are drawn to scale. Have the students use a ruler to make an accurate depiction.
  6. Explain to the students that they are soil scientists that have been hired to help figure out past environmental conditions.
  7. Give the students the questions as a data sheet to fill out and to explain past environmental conditions.
Questions:
  1. Based on your soil profile, what is the depth of the first layer in the profile? What environmental conditions could have led to the deposition of this layer?
  2. What is the depth of the second layer? Do you think that the environmental conditions at the time that this layer was deposited would have been productive to plant growth? Why?
  3. The third layer is sand. What environmental conditions could have been responsible for the deposition of the sand?
  4. What does this last layer in this soil profile tell you about the environmental conditions?
  5. Label the soil samples A B C and D starting from the bottom.
  6. Which soil profile demonstrates a drought condition?
  7. Which soil profile demonstrates deposition by a river or stream?
  8. Which profile demonstrate high amounts of plant growth?
  9. Which soil sample demonstrates a very slow stream or lake?
  10. Based upon the soil profiles that you have observed, prepare a 1 page report to the USGS that explains past environmental conditions.