1. The four components of soil:
What Is Soil?
Soil is the layer of rock and mineral fragments along with organic matter, water and air that supports the growth of plants.
The four components of soil:
Decomposed rock
Humus
Air
Water

2. Dirt is what gets on your clothes and into your house
What is Dirt?
Dirt is what gets on your clothes and into your house

3. Controls on Soil Formation
Parent material – Bedrock vs. Unconsolidated
Time – longer time, more soil
Climate – temperature and precipitation
More plants and animals = more organic matter
Poorly developed soils on steep slopes

4. Soil Texture and Structure
Point A:
10% silt
40% clay
50% sand
Clay loam has no single particle size percentage that dominates!

5. Controls of Soil Formation
If the parent material is bedrock, then we get residual soils
On unconsolidated sediments, we get transported soils

6. How quickly is soil formed?
Soil composition
-Soil forms in layers
-Larger materials are found on the bottom
How quickly is soil formed?
-It may take several hundred years for 1cm to form

7. Soil profile
A vertical column showing the sequence of layers of particles in the soil

8. Soil Horizons -A distinct layer or zone within a profile
-There are four major zones (O, A, B, C)
O zone -Leaf litter, high decomposition
A Zone
-High organic matter
-Generally the darkest in color
-High humus content
B Zone
-Less developed
-Lighter in color
-Zone of accumulation (highly soluble mineral build-up)
-Red or brown in color
-Clay accumulated (Hard pan formation)
C Zone
-Contains weather parent material

9. Soil Horizons O zone -Leaf litter, high decomposition A Zone
-High organic matter
-Generally the darkest in color
-High humus content
B Zone
-Less developed
-Lighter in color
-Zone of accumulation (highly soluble mineral build-up)
-Red or brown in color
-Clay accumulated (Hard pan formation)
C Zone
-Contains weather parent material

10. Rill and Gully Erosion

11. Eroded channels ranging in size from rivulets to small gullies caused mainly by runoff waters rather than raindrop dislocation.

12. Gully erosion in Tanzania. What is the main factor for it’s cause?

13. Who cares about soil erosion?