Soil production function refers to the rate of
bedrock weathering
Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...
into
soil
Soil, also commonly referred to as earth or dirt
Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty.
Common types of dirt include:
* Debri ...
as a function of soil thickness.
A general model suggested that the rate of physical
weathering
Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...
of bedrock (de/dt) can be represented as an exponential decline with soil thickness:
where ''h'' is soil thickness
''P
0''
m/yearis the potential (or maximum) weathering rate of bedrock and ''k''
−1is an empirical constant.
The reduction of weathering rate with thickening of soil is related to the exponential decrease of
temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer.
Thermometers are calibrated in various Conversion of units of temperature, temp ...
amplitude with increasing depth below the soil surface, and also the exponential decrease in average water penetration (for freely-drained soils). Parameters ''P
0'' and ''k'' are related to the
climate
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...
and type of parent materials. found the value of ''P
0'' ranges from 0.08 to 2.0 mm/yr for sites in
Northern California, and 0.05–0.14 mm/yr for sites in Southeastern
Australia. Meanwhile values of ''k'' do not vary significantly, ranging from 2 to 4 m
−1.
A number of
landscape evolution models have adopted the so-called ''humped'' model.
The humped soil production function
Arjun Heimsath. Arizona State University, Earth and Space Exploration This model dates back to G.K. Gilbert's ''Report on the Geology of the Henry Mountains'' (1877). Gilbert reasoned that the weathering
Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...
of bedrock was fastest under an intermediate thickness of soil and slower under exposed bedrock or under thick mantled soil. This is because chemical weathering
Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...
requires the presence of water. Under thin soil or exposed bedrock water tends to run off, reducing the chance of the decomposition of bedrock.
See also
* Biorhexistasy
*Hillslope evolution Hillslope evolution is the changes in the erosion rates, erosion styles and form of slopes of hills and mountains over time.
Conceptual models
During most of the 20th century three models of hillslope evolution were widely diffused: slope decline, ...
*Parent material
Parent material is the underlying geological material (generally bedrock or a superficial or drift deposit) in which soil horizons form. Soils typically inherit a great deal of structure and minerals from their parent material, and, as such, are ...
*Pedogenesis
Soil formation, also known as pedogenesis, is the process of soil genesis as regulated by the effects of place, environment, and history. Biogeochemical processes act to both create and destroy order ( anisotropy) within soils. These alterations ...
* Soil functions
*Weathering
Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement) ...
References
Bibliography
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{{soil science topics
Mathematical modeling
Pedology