Types & Development Earth Science Rocks!

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

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.

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

Sample from a Soil Probe

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

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

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

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

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.