Soil forms when weathered parent material interacts with environment. SOIL FORMATION Soil forms when weathered parent material interacts with environment.

weathering Wearing parent material down PHYSICALLY CHEMICALLY

Physical (Mechanical): disintegration of parent material into smaller pieces increases surface area: surface area increases by about the same factor as particle size decreases.

Chemical (Biogeochemical) acts on surfaces: primary minerals are broken down and secondary minerals are formed.

Soil forms when weathered parent material interacts with the environment. What would constitute the ENVIRONMENT of a soil?

Soil carbonic acid (formed from LIFE in soil) extracts minerals from soil (which came from parent material)

How fast does soil form? Not very. Slow--------------------------------------Fast ~ 1 cm/1000 yr ~ 30cm/50yr

Hans Jenny 1941: soil is open system, properties are functionally related; system changes when property(ies) change(s). Jenny’s CLORPT equation s = ƒ (cl, o, r, p, t) He expanded on the ideas of Dokuchaev

1. CLIMATE 2. ORGANISMS 3. RELIEF 4. PARENT MATERIAL 5. TIME

1. CLIMATE …determines speed, character of soil development: determines the type and rate of weathering determines living organisms and plants found in an area

components of climate : 1. Temperature -for every 10°C , biochemical rxn rates 2X 2. Effective precipitation (water that moves through entire soil column, including regolith) -depth of water = depth of weathering -water moves soluble & suspended materials

(Fig. 2.15) High temperatu

Temperature and humidity increase the depth of weathering. High latitude Humid, tropics Dry, SW US Humid, SE US

Effective precipitation -a) seasonal distribution -b) temperature, evaporation -c) topography -d)permeability

a) Seasonal distribution of precipitation: Location B 600 mm/yr Location A 600 mm/yr 100mm 50mm 6 rainy months only Every month

b) Temperature and evaporation: Location A hot Location B cool High evapotranspiration Low evapotranspiration 600 mm 600 mm Lower effective ppt Higher effective ppt

Topography: concave or bottom of slope (receiving) level slope

Permeability:

2. Organisms plant and animal (Living plants and animals on and in soil) -sources of organic matter -nutrient recycling -vegetation prevents erosion -type of vegetation influences soil type -base pumping -

Type of vegetation influences soil type

Base pumping Deciduous trees are more effective base pumpers than conifers . -needles are hard to break down -basic cations leach away: soil is acidic -deciduous litter is easy to break down -cations (bases) are released so surface soils are not acidic

Macroanimals (insects, mammals, gastropods, earthworms) mix, bind soil; create channels for air, water

crotovinas

night crawlers and water

Macroanimals (insects, mammals, gastropods, earthworms) mix, bind soil; create channels for air, water Microanimals (nematodes, protozoa)

Macroanimals (insects, mammals, gastropods, earthworms) mix, bind soil; create channels for air, water Microanimals (nematodes, protozoa) Macroplants (the green plants) provide organic matter, roots create channels, adsorb nutrients, release CO2, stabilize, protect from erosion

Macroanimals (insects, mammals, gastropods, earthworms) mix, bind soil; create channels for air, water Microanimals (nematodes, protozoa) Macroplants (the green plants) provide organic matter, roots create channels, adsorb nutrients, release CO2, stabilize, protect from erosion Micro “plants” (fungi, bacteria, actinomycetes, algae) decomposers

3. Relief/Topography important for rate of runoff, erosion, drainage

Flat valley floors and flat ridge tops: soil accumulates; (deepening>removal) Slopes: (removal> deepening)

4. Parent Material Determines: texture, types of weathering, mineral make-up

Some Physical Weathering Processes: 1. Freeze/thaw

Freeze / Thaw

Physical: 1. Freeze/thaw 2. Exfoliation

2. Exfoliation (unloading)

Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion

3. Abrasion (wind, water, ice)

water

ice

Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion 4. Salt wedging

4. Salt Wedging

Physical: 1. Freeze/thaw 2. Exfoliation 3. Abrasion 4. Salt wedging 5. Root wedging

5. Root Wedging

Chemical (biogeochemical): 1. Hydrolysis: minerals react with H2O H+ replace soluble parts; OH- combine with mineral cations 2. Hydration: mineral combines with H2O 3. Oxidation: mineral combines with O2 (lose electron) Reduction: loss of O2 (gain electron) 4. Carbonation: oxides combine with acids to make carbonates 5. Complexation: organic acids form organic complexes with metal cations

5. Time Amount of time soil has been exposed to weathering and soil forming processes influences soil properties. Jenny’s staircase Ohio/Ky.

4 soil forming processes: (pedogenic) Transformation

4 soil forming processes: Transformation Translocation

4 soil forming processes: Transformation Translocation Addition

4 soil forming processes: Transformation Translocation Addition Loss