1. Composition Formation Erosion Profile
SOIL
Composition
Formation
Erosion
Profile

2. Soil Composition Soil is a mixture of . . . Humus (decaying organisms)
Sediment (weathered bits of rock;
determines soil texture)
Water
Air
50% solids, 25% liquid, % gases/pore spaces

3. Soil Formation Humus: from the decay of organic matter Vegetation
Animals
Fungi

4. Soil Formation Sediment: from the weathering of rock
Bedrock—weathers at location of soil formation
Regolith—loose rock on top of bedrock
Sediment—brought in from another location via erosion

5. Rate of Soil Formation Factors that speed/slow soil formation:
Hardness of parent rock: lower = faster
Time: more = more
Slope: steeper = faster
Vegetation: more = faster
Animals: more = faster
CLIMATE (most important):
wetter = faster

6. Rate of Soil Erosion
Increases dramatically with the amount of people in an area
Activities that increase soil erosion:
Farming
Logging
Roads
Removing vegetation

8. O A E B C R Soil Profile …is a group of soil horizons (layers)
O: humus
A: sediment & humus mix
E: minerals leach out of sediment & seep down
B: seeped minerals from horizon E collect here
C: partially weathered bedrock
R: unweathered bedrock

9. Soil Texture Activity

10. Soil Texture Activity Loam — mixture of sand, silt, and some clay
Texture is rough & spongy
Ideal for plants -
Enough porosity for roots to get air without losing all water & nutrients