EVSC10001 Lecture Notes - Lecture 24: Regolith, Weathered, Soil Horizon
10 Jun 2018
School
Department
Course
Professor
Soil: mixture of organic matter, minerals, gases, liquids, and organisms that
together support life
Product of continuous processes over time
Transformation (weathering)
○
Translocation
○
-
ULTIMATE PRODUCT OF ROCK WEATHERING
-
Horizons are formed in suit on a stable surface as a result of pedogenesis ->
soil isn't a deposit
-
Weathering leads to …. Soil!!
Soil is upper layer in regolith
-
Soil components + properties
25% air
-
25% water
-
45% mineral particles
-
5% organic matter
-
Colour determined by minerals
-
Soil built from microaggregates and aggregates
Formation dependent on presence of water + affected by changing
conditions (eg. Change in pH or redox)
○
-
Peds are macro-aggregates (<1mm) formed from pedogenic (processes in
soil) processes - separated by pores or voids
-
Soil formation
Neoformation - transformation processes (weathering) (internal reactions)1.
Mineral transforms - eg clays
-
Minerals form from solution eg. Carbonate
-
Mineral formation from host rock
-
Translocation processes (clay illuviation, carbonate leaching, mixing by soil
organisms) (internal movement)
2.
Movement with water or soil organisms - bioturbation
-
Leaching - movement of matter dissolved in soil
-
Illuviation: introduction of salts into one soil horizon from antoher by
percolating water
-
Losses3.
Water erosion
-
Wind erosion
-
Addition 4.
Rainfall brings new material
-
Deposition - wind, floods
-
Organic material
-
Soil horizons (not layers)
O horizion -dark orgnaic matter - rich surface
Humus
○
-
A horizon - organic and mineral matter
Top soil
○
-
B horizon -zone of accumulation
-
E horizon -zone of mineral/organic losses (leached)
-
C horizon -slightly altered parent material (bedrock, regolith…)
Weathered bedrock
○
-
-
Factors in soil development
Lithology, climate, vegetation, relief/topography, time, humans
-
Topo-sequence = sequence of varying profiles along changing
relief/topography (comparable parent material)
-
Chrono-sequence = sequence in substrates of varying age (comparable
parent material)
-
Soil types
Thick A horizon
Humification
○
Bioturbation
○
-
Mollisols: semiarid + subhumid graslsands with dark humus-rich epipedone
-
Histosols: thick layer of organic matter
-
Gleysols: hydromorphic soils saturated with ground water for long enough to
develop colour pattern
-
Spodosols: cold, moist climates, well-developed B horizon of clay illuviation
Spodic horizon - mixture of organic matter and compounds of
aluminium and iron- brought down by leaching from E horizon
○
-
Alfisols: humid and subhumid climates w/ subsurfac ehorizon of lcay
accumulation by eluviation and illuviation
-
Oxisols: very old
-
Aridisols: dry climates, low organic matter
-
Vertisols: soils with high clay content + deep cracks when dry
-
Buried soils -Paleosols
Buried, past land surface
-
Landscape archive
-
Functions of Soil
Agriculture
Capillary action and moisture storage (cohesion, adhesion)
○
Natural cycling of nutrients - altered by agriculture
Fertilizer -> more leaching
§
○
Soil provides essential elements for PLANT NUTRITION
○
-
-
Soil Erosion
Soil quality degraded by:
Excessive crop growth -> strip soil nutrients
○
Overuse of pesticides
○
Industrial contamination
○
Salt build-up
○
-
Soil only formed if formation rate > erosion!
Slow formation + not easily replaced
○
-
Soils
Thursday, 7 June 2018
10:55 pm
Soil: mixture of organic matter, minerals, gases, liquids, and organisms that
together support life
Product of continuous processes over time
Transformation (weathering)
○
Translocation
○
-
ULTIMATE PRODUCT OF ROCK WEATHERING
-
Horizons are formed in suit on a stable surface as a result of pedogenesis ->
soil isn't a deposit
-
Weathering leads to …. Soil!!
Soil is upper layer in regolith
-
Soil components + properties
25% air
-
25% water
-
45% mineral particles
-
5% organic matter
-
Colour determined by minerals
-
Soil built from microaggregates and aggregates
Formation dependent on presence of water + affected by changing
conditions (eg. Change in pH or redox)
○
-
Peds are macro-aggregates (<1mm) formed from pedogenic (processes in
soil) processes - separated by pores or voids
-
Soil formation
Neoformation - transformation processes (weathering) (internal reactions)1.
Mineral transforms - eg clays
-
Minerals form from solution eg. Carbonate
-
Mineral formation from host rock
-
Translocation processes (clay illuviation, carbonate leaching, mixing by soil
organisms) (internal movement)
2.
Movement with water or soil organisms - bioturbation
-
Leaching - movement of matter dissolved in soil
-
Illuviation: introduction of salts into one soil horizon from antoher by
percolating water
-
Losses3.
Water erosion
-
Wind erosion
-
Addition 4.
Rainfall brings new material
-
Deposition - wind, floods
-
Organic material
-
Soil horizons (not layers)
O horizion -dark orgnaic matter - rich surface
Humus
○
-
A horizon - organic and mineral matter
Top soil
○
-
B horizon -zone of accumulation
-
E horizon -zone of mineral/organic losses (leached)
-
C horizon -slightly altered parent material (bedrock, regolith…)
Weathered bedrock
○
-
-
Factors in soil development
Lithology, climate, vegetation, relief/topography, time, humans
-
Topo-sequence = sequence of varying profiles along changing
relief/topography (comparable parent material)
-
Chrono-sequence = sequence in substrates of varying age (comparable
parent material)
-
Soil types
Thick A horizon
Humification
○
Bioturbation
○
-
Mollisols: semiarid + subhumid graslsands with dark humus-rich epipedone
-
Histosols: thick layer of organic matter
-
Gleysols: hydromorphic soils saturated with ground water for long enough to
develop colour pattern
-
Spodosols: cold, moist climates, well-developed B horizon of clay illuviation
Spodic horizon - mixture of organic matter and compounds of
aluminium and iron- brought down by leaching from E horizon
○
-
Alfisols: humid and subhumid climates w/ subsurfac ehorizon of lcay
accumulation by eluviation and illuviation
-
Oxisols: very old
-
Aridisols: dry climates, low organic matter
-
Vertisols: soils with high clay content + deep cracks when dry
-
Buried soils -Paleosols
Buried, past land surface
-
Landscape archive
-
Functions of Soil
Agriculture
Capillary action and moisture storage (cohesion, adhesion)
○
Natural cycling of nutrients - altered by agriculture
Fertilizer -> more leaching
§
○
Soil provides essential elements for PLANT NUTRITION
○
-
-
Soil Erosion
Soil quality degraded by:
Excessive crop growth -> strip soil nutrients
○
Overuse of pesticides
○
Industrial contamination
○
Salt build-up
○
-
Soil only formed if formation rate > erosion!
Slow formation + not easily replaced
○
-
Soils
Thursday, 7 June 2018 10:55 pm
Document Summary
Soil: mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Horizons are formed in suit on a stable surface as a result of pedogenesis -> soil isn"t a deposit. Formation dependent on presence of water + affected by changing conditions (eg. change in ph or redox) Peds are macro-aggregates (<1mm) formed from pedogenic (processes in soil) processes - separated by pores or voids. Translocation processes (clay illuviation, carbonate leaching, mixing by soil organisms) (internal movement) Movement with water or soil organisms - bioturbation. Leaching - movement of matter dissolved in soil. Illuviation: introduction of salts into one soil horizon from antoher by percolating water. O horizion - dark orgnaic matter - rich surface. E horizon - zone of mineral/organic losses (leached) C horizon - slightly altered parent material (bedrock, regolith ) Topo-sequence = sequence of varying profiles along changing relief/topography (comparable parent material) Chrono-sequence = sequence in substrates of varying age (comparable parent material)
