2: How Do Soils Form? Flashcards
5 soil forming factors
Parent material
Climate
Organisms
Topography
Time
4 soil forming processes
Addition of materials
Loss of materials
Translocations
Transformations
Soil profile
The vertical arrangement of soil horizons
Order of soil horizons
O: organic materials
A: topsoil
E: loss of material, eluviated zone
B: subsoil
C: weathered rock
R: solid rock
Felsic rock
Made out of light elements
Mafic rock
Made out of heavy elements
6 master horizons
The most common horizons found in developed soils (not all are always found)
Transition horizons
May be dominated by properties of one horizon but have properties of the other
Subordinate distinctions
Horizon suffixes applied to further describe master horizons
What are the 4 different unique environment distinction horizons
M, L, V, W
M horizon
Human-made layer (asphalt, landfill, liner)
L horizon
Horizon of biologically produced material deposited in water
V horizon
Horizon dominated by vesicular pores
W horizon
Water (liquid or frozen)
Entisol
Soils with little or no profile development
Inceptisol
Soils with subtle profile development
w: reddening or change in soil structure
Andisol
Soils developed from volcanic ejecta and volcanic ash
High fertility
Gelisol
Soils with permafrost: W layer
Permafrost is a layer of frozen soil for more than 2 consecutive years
i: slightly decomposed organic material (OM)
e: intermediately decomposed OM
f: frozen
Histosol
Comprised mainly of organic vs. mineral matter
~20% or more organic
Fibric (Oi) - slightly decomposed
Hemic (Oe) - moderately decomposed
Sapric (Oa) - highly decomposed
Aridosol
Desert soils, subsoil clay and carbonates/salt accumulation
V: vesicular pores
k: accumulation of CaCO3
m: cemented
Vertisol
Self-churning soils by shrink-swell process
ss: slickensides (surfaces on the soil that are shiny)
BC: transitional between B and C properties
Mollisol
Soils with thick surface accumulation of soil organic matter
t: illuvial accumulation of clay
k: accumulation of CaCO3
BC: transitional between B and C properties
Alfisol
Soils with subsurface accumulation of clays
High base saturation (Na, K, Ca, Mg)
t: accumulation of translocated clay
1, 2: distinctive layers with different texture and/or color exist within the same horizon
Ultisol
Highly weathered soils with subsurface accumulation of clay and low base saturation (low fertility)
Developed under most warm conditions. In the US only in the south east (North, South Carolina, Alabama)
i: slightly decomposed organic material (OM)
p: plowed
g: graying, prolonged soil water saturation resulting in the reduction of iron leading to dull gray coloration
Spodosol
Common in boreal forests
Defined by the process of podzolization
e: intermediate decomposition
s: illuvial accumulation of Fe and Al oxides with OM
h: illuvial accumulation of humus
BC: transitional between B and C
r: soft or weathered bedrock (used with C)
Oxisol
Completely weathered soils
Strongly weathered, few (<10%) weatherable minerals, predominantly Fe and Al oxyhydroxides
p: plowed
o: residual accumulation of Fe and Al oxides
State factor equation
S = f(cl, o, r, p, t)
Soil is the result of climate, organisms, parent material, topography, and time
