Soil Horizons Flashcards
O
Layer of organic material that has undergone physical and chemical breakdown. Usually top-most layer. Common in forests and absent in grasslands. Dark in color.
A
Layer beneath the O horizon that is dominated by mineral particles but have darkened due to the accumulation of organic material.
E
Layer beneath A and above B horizon that is lighter in color than both layers above and below it. These are areas of intense weathering, or elluviation, that are devoid of organic matter, clay, and iron/aluminum Usually occur in forests and rarely in grasslands.
B
Layer beneath A and sometimes E that consists largely of silicate clays and iron/aluminum oxides that have washed in, or illuviated, from the above layers.
C
Unconsolidated material underlying the solum, below the zone of greatest biological activity. In dry regions, gypsum and carbonates may be concentrated.
R
Consolidated rock with little evidence of weathering.
a
Highly decomposed organic matter
b
Buried soil horizon
c
concretions or nodules
co
Coprogenous Earth
d
Dense, unconsolidated material
di
diatomaceous earth
e
intermediately decomposed organic matter
f
frozen soil
ff
Dry Permafrost
g
strong gleying (mottling)
h
illuvial accumulation of organic matter
i
slightly decomposed organic matter
j
Jarosite (yellow sulfate mineral)
jj
cryoturbation (frost churning)
k
accumulation of carbonates
kk
engulfment of carbonates (>50% of soil by mass)
m
cementation or induration
n
accumulation of sodium
o
accumulation of iron and aluminum oxides
p
plowing or other human disturbance
q
accumulation of silica
r
weathered of soft bedrock
s
illuvial organic matter, iron and aluminum oxides
se
presence of sulfides
ss
slickenslides (shiny clay wedges)
t
Accumulation of silicate clays
u
human manufactured artifacts
v
plinthite (high iron, red material)
w
distinctive color or structure without clay accumulation
x
fragipan
y
accumulation of gypsum
yy
engulfment of gypsum (>50% of soil by mass)
z
accumulation of soluble salts
Diagnostic soil horizon
presence or absence of certain layers which help to determine where to place a soil within the classification system
Epipedons
Diagnostic horizons that occur at the soil surface.
Mollic
Mineral Surface horizon noted for its dark color associated with accumulated organic matter, thick and soft, high base saturation, moist at least 3 months of the year when the soil temp is 5C or higher to a depth of 50cm. Characteristic of Grasslands.
Umbric
Similar to mollic but with lower base saturation. Common in areas of higher rainfall, and where the parent material has lower calcium and magnesium content
Ochric
mineral horizon that is too thin too light in color or too low in organic matter to be mollic or umbric. Usually not as deep as mollic or umbric. Tends to be hard and massive when dry.
Melanic
very black mineral horizon due to its high organic matter content, a result of volcanic ash. Light and Fluffy.
Histic
Organic soil materials overlying a mineral soil. Formed in wet areas, this layer is peat or muck. Has low bulk density.
Diagnostic Subsurface horizons
Other layers that help to further identify and classify a soil.
Argillic
Accumulation of silicate clay that have moved down from the upper horizons or have formed in place.
Natric
silicate clay accumulation with 15% available sodium on the colloidal complex. Found mostly in arid or semi arid areas.
Oxic
Highly weathered subsurface horizon that is very high in iron and aluminum oxides and inlow activity silicate clays. Found mostly in humid tropical and subtropical regions. This horizon is crumbly and not very sticky despite high clay content.
Kandic
accumulation of iron and aluminum oxides and low activity clay but clays skins need not be present
Spodic
an illuvial horizon that is characterized by the accumulation of colloidal organic matter and aluminum oxide. Commonly found in highly leached forest soils of cool humid climates.
Sombric
illuvial horizon dark in color with high organic material. Low base saturation. Found in cool moist soils of high plateaus and mountains in tropical and subtropical regions.
Albic
light colored eluvial horizon that is low in clay and oxides of iron and aluminum.
Calcic
contain accumulations of carbonates that often appear as white nodules
Fragipan
materials are cemented or densly packed resulting in an impermeable layer
Mollisol
dark soft soils of grasslands. accumulation of calcium rich organic matter. suffix -olls
entisol
Weakly developed mineral soils without genetic horizons or with only beginning of horizons. Productivity ranges from very low to very high. Suffix -ents
Inceptisols
Few diagnostic features, possible cambic layer. suffixt -epts
Andisols
Volcanic ash soils. melanic epipedon. Suffix -ands
Gelisols
Young soils with little development. Cold temperatures and frozen conditions. suffix -els
Histosols
Little profile development due to low oxygen conditions. accumulation of partly decomposed organic parent material. Suffic -ists
Aridisols
dry soils, aridity is a defining characteristic. less than 90 days of plant growing water per year. suffix -ids
Vertisols
Dark swelling, cracked clays. main soil forming process is the shrinking and swelling of clays through periods of drying and wetting. dark blackish. Suffix -erts
Ultisols
Clay mineral weatthering is the principle soil forming process, translocation of clays to accumulate in an argillic or kandic horizon. wet conditions. suffix -ults
alfisols
argillic or natric horizon. Suffix -alfs. semi arid to humid climates.
spodosols
acid sandy forest soils that are highly leached. suffix -ods
Oxisols
oxic horizon, highly weathered. hot climates with year round moisture conditions. ochric or umbric epipedon. sufix -ox
