Chapter 2
Soil Origin and
Development
T2-1
Soil Science & Management, 4E
Objectives
•
•
•
•
T2-2
Define a soil body
List examples of five soil-forming factors
Describe how soils develop
Describe the horizons of a soil profile
Soil Science & Management, 4E
Terms to Know
•
•
•
•
•
•
•
•
•
•
•
T2-3
Alluvial fan
Alluvial soil
Chemical weathering
Colluvium
Delta
Eluviation
Eolian deposit
Floodplains
Frost wedging
Glacial drift
Glacial outwash
•
•
•
•
•
•
•
•
•
•
•
Glacial till
Hydrolysis
Igneous rock
Illuviation
Lacustrine
Leaching
Levee
Loess
Marine sediment
Master horizon
Metamorphic rock
(continued)
Soil Science & Management, 4E
Terms to Know
T2-4
•
•
•
•
•
•
•
•
•
•
•
•
Mineral soil
Organic soil
Oxidation-reduction
Parent material
Pedology
Pedon
Physical weathering
Plow layer
Polypedon
Residual soil
River terrace
Root wedging
•
•
•
•
•
•
•
•
•
•
•
Sedimentary rock
Soil genesis
Soil horizon
Soil profile
Solum
Solution
Subsoil
Talus
Topsoil
Transported soil
Weathering
Soil Science & Management, 4E
The Soil Body
Figure 2-1
T2-5
Soil Science & Management, 4E
Rocks and Minerals
• Igneous rock
• Sedimentary rock
• Metamorphic rock
T2-6
Soil Science & Management, 4E
Rocks and Minerals
Figure 2-4
T2-7
Soil Science & Management, 4E
Igneous Rock
Figure 2-5
T2-8
Soil Science & Management, 4E
Metamorphic Rock
Figure 2-6
T2-9
Soil Science & Management, 4E
Parent Material
Figure 2-8
T2-10
Soil Science & Management, 4E
Parent Material
•
•
•
•
•
•
Glacial ice
Wind
Water
Gravity
Volcanic deposits
Organic deposits
Figure 2-9
Figure 2-11
T2-11
Soil Science & Management, 4E
Climate
Figure 2-13
T2-12
Soil Science & Management, 4E
Organisms
Figure 2-14
T2-13
Soil Science & Management, 4E
Topography
• Influences soil development mainly
by affecting water movement
T2-14
Soil Science & Management, 4E
Time
• Soils change over time due to
aging process
• Humans
T2-15
Soil Science & Management, 4E
The Soil Profile
• Master horizons
• Subdivisions of
master horizons
Figure 2-19
T2-16
Soil Science & Management, 4E
Summary
• Soils form from minerals broken up by
action of weathering, plant roots, and the
addition of decaying plant parts
• Five factors govern soil development:
- Parent material
- Climate
- Life
- Topography
- Time
T2-17
Soil Science & Management, 4E