1. Types & Development
Earth Science Rocks!

2. 2. Soil Soil is a combination of _____________ and an ______________.
a. ________- is decayed plant and animal material found in soil. Soil that contains 20% to 30% humus is considered rich for plant growth.
weathered rock
organic matrix
humus

3. What is a Soil Profile?
A soil profile is a view of a cross section of soil.
Depending on a few characteristics like climate, vegetation, location, etc, soils will have varying properties as seen below.

4. c. The soil Profile- development of the layers
Top soil  “A horizon”
-Top layer of soil rich in humus
- most weathered
- fine to small particle size
HUMUS
Sub soil  “B horizon”
-Consists of clays & dissolved minerals washed down from above; -contains little humus
- small to medium particle size
C horizon- partly weathered rock
- Consists of partly weathered bedrock
- has trace amounts of humus
Bedrock
-layer of solid rock beneath the soil
- parent rock of the soil above
- no organic material/least weathered

5. Sample from a
Soil Probe

6. Immature soil Mature soil Stage 1 Stage 2 Stage 3 TIME INCREASES
(development takes thousands of years)

7. Discussion Questions
1. What are the three requirements for soil development?
Time
Weathering
Organic Material
2. Soil characteristics will be influenced by:
Parent Rock
Climate

8. Discussion Questions
3. Organic material is located in horizon A. How is organic material transported from horizon A to horizon B?
Leaching the process of seeping down
4. State the relationship between time and soil depth.
As time increases, soil depth increases as well
time
depth

9. Soil Horizons Worksheet (Answers)3
7,11,13
16,17,18 20 1
9,10 14 19 2 15
6,8
5,12 4

10. Characteristics of the Soil Horizons
0 Horizon-located on surface, mostly O.M.
A Horizon-Called Topsoil, good amounts of O.M. and minerals.
B Horizon- Known as Subsoil, Less O.M.
C Horizon- Mostly parent material, does little for plant growth.