1. Soils & Soil Formation-The Results of Weathering

2. Regolith
A layer of weathered rock fragments
covers much of the Earth’s surface

3. Regolith

4. Soil
part of the regolith that supports plant growth
Complex mixture of minerals, water, gases, and remains of plants and animals

5. What is Soil Composition?
has 4 major components:
mineral matter
organic matter (humas)
water
air

7. Composition of Soil:

8. What is Humus?
Dark, organic material, remains of animals and plants

9. Humus:

10. - Sand (large size) - Silt - Clay (small size)
 What are the Soil Textures?
• Texture refers to the proportions of different particle sizes.
- Sand (large size)
- Silt
- Clay (small size)
• Loam (a mixture of all three sizes) is best suited for plant life.

11. CLAY

12. SILT

13. SAND

14. Soil Texture

15. source of the mineral matter in soil
What are the most important factors in soil formation?
(1) parent material
source of the mineral matter in soil

16. • Residual soil—parent material is the bedrock below the soil
• Transported soil—has been carried from parent material and deposited elsewhere

17. (2) Time (3) Climate • Greatest effect on soil formation
• Important in all geologic processes
• The longer a soil has been forming, the thicker it becomes.
(3) Climate
• Greatest effect on soil formation

18. (4) Organisms
• Organisms influence the soil's physical and chemical properties.
• Furnish organic matter to soil
(5) Slope
Steep slopes often have poorly developed soils.
Direction the slope is facing influences soil formation (affects soil temperature and moisture)

19. Thinner on slope because water erodes soil & deposits it down the slope

20. Tends to be
thicker here
(deposited)

21. What is a Soil profile?
A cross-section in which the layers of the soil and bedrock can be seen
Each layer is called a horizon.
In fully developed residual soil, there are three horizons

22. B horizon (subsoil) A horizon (topsoil)
mixture of organic matter and small rock particles
B horizon (subsoil)
contains minerals and clay

23. partially weathered bedrock
C horizon (regolith)
partially weathered bedrock

24. Bedrock
Solid, unweathered rock that lies beneath regolith

25. Bedrock

32. What role does Climate play in soil formation?
Climate is most important factor influencing soil formation

33. What is a Temperate climate?
Temperatures range from cool to warm
Rain fall is not excessive
Two types of soil are found dependent on amount of rainfall:

34. What are the soil types of temperate climates?
Pedalfer – soil formed if an area receives 65 cm or more of rain per year (clay, quartz, iron)
-found in eastern United States
2. Pedocal – soil formed if rainfall is less then 65 cm a year (calcium carbonate)
-found in western United States

35. Pedalfer

36. Pedocal

37. What is the soil formation in tropic areas?
forms laterites (thick and infertile soil)
*rain always is washing away the A horizon but constant rotting vegetation covers the B Horizon

38. Laterite

39. What is soil formation of a desert?
Forms soils from mechanical weathering
Soil is thin and mostly of regolith