1. The Formation of Soil
Earth Science
Mr. Cloud

2. Soil Formation
Soil: is a mixture of rock particles and organic matter on Earth’s surface that supports rooted plants

3. How do soils form?
Soils form from the weathering of bedrock, over time soil develops horizontal layers with distinct profile
Physical and chemical weathering are vital to the formation of soil
Living things play a significant role in soil formation

4. Soil Composition
25%
45%
25% 5%

5. What are some factors that affect the type of soil found in a region?
1. Climate: temperature and moisture conditions affect the rate of weathering
i.e. more water available, faster weathering, faster soil development
i.e. Too much water can be harmful; waste away nourishment from the soil
i.e. Too little water, little vegetation, less soil development

6. What are some factors that affect the type of soil found in a region?
2. Gradient:
steep slopes will cause rock to fall under the force of gravity; runoff of precipitation tends to amplify erosion
Moderate slopes and valleys encourage the formation of deep soils
3. Organisms: animal/plant life affects the soil

7. Soil Organisms Earthworms provide many soil services
One teaspoon of fertile soils contains millions of microorganisms such as bacteria, fungi, algae, microscopic worms, and protozoa!
Ecosystem Services: organisms help maintain soil fertility, prevent soil erosion, breakdown toxic materials, cleanse water, and affect the composition of the atmosphere.
Earthworms provide many soil services

8. Soil Horizons

9. Mature Soil Profile: temperate location
Mollisol: similar to the mature organic-rich soils of the American “bread-basket”

11. Immature Soil Profiles
Alfisol
Immature Soil Profiles
Aridisol