Physical Geography Test 4 (soils)
Oxisols
(also called laterites)--They have been thoroughly leached and oxidized. These are common in the wet tropics.
Soil texture
Is the combination of particle size present in a soil
Parent Material
Is the mineral content of the soil
Reduction
Is the opposite of oxidation and occurs where there is no oxygen
Inorganic component
Is the product of chemical weathering
Histosols
are very high in organic matter. They form in waterlogged environments, like swamps and marshes. These are mostly peats and form under the pedogenic regime of gleization. Histosols are most common in cold environments.
Caliche (calcrete)
Frequently in deserts calcium is leached down a short distance and accumulates, becoming a hard layer known as
Peat
In poorly drained areas, like swamps, the organic matter does not decompose, which leads to the development of
Laterite
In some instances, the iron, aluminum and quartz sand form a hard surface
Vegetation
Is also climate controlled to a large extent
Gley soils
Is formed from reduction
Clay soils
Mostly clay sized particles
Sandy soils
Mostly sand sized particles
Silty soils
Mostly silt sized particles
A
Organic and mineral- much biol. activity
E horizon to B horizon
Water moving down through the soil carries soluble minerals and clays
Residual material
Weathered bedrock that stays in place
E
Zone of Eluviation
B
Zone of illuviation
Spodosols
form in areas like those of Ultisols, except it is colder and the mineral component is sand (infertile)
Aridisols
form in deserts and semideserts. Because water is scarse and does not penetrate far, the horizons are very thin. There is little organic matter present Frequently, salts build up near the surface, either in layers or chunks. Caliche is common in these areas.
Ultisols
generally form under forests with a dry season. They have had much leaching but less than Oxisols. These are common in the Southeastern U.S.
A horizon
gets mixed with mineral matter below the surface
acidity
of a soil also affects the plants growing in it
Andisols
soils of volcanic areas.
anions
Clay and humus particles tend to be
cations
Clay and humus particles tend to attract
Regolith C layer
Beneath the B layer is a layer of broken rock fragments
Aggregates (or dirt clots)
Change the characteristics of the soul in such factors as erosion and water holding
Soil
Organic and inorganic material licated above the bedrock and capable of supporting life
O
Organic layer- decomposed or not
O layer
Organic matter falls on the surface
C
Regolith
Loams
Soils with significant amounts of clay, sand, and silty soil
Transported material
That was weathered elsewhere, eroded and deposited at its present location
Illuviation
The B horizon collects the minerals from the E layer
Seventh Approximation
The current classification scheme for soils was developed mostly by the U.S.D.A. and is commonly known as the
Leaching or Eluviation
The downward movement of water carrying minerals
Vertisols
are distinct because of the high content of swelling clays, which churns the soil frequently. What we call adobe is a vertisol.
Alfisols
are transitional from the calcification regions of Mollisols and the Podzolization regions of the Ultisols and Spodosols. They are found in the Southern Great Lakes region (the Corn Belt).
cation exchange
capacity is a measure of the soil's ability to hold cations, and, so, is a measure of the fertility of the soil
swelling clays
clay swell when they get wet and contract when they dry. Mudcracks are an indication of the presence
Mollisols
develop under mid latitude grasslands. They have an A layer rich in organic matter and have relatively little leaching, due to low rainfall amounts. Calcification occurs here. The Great Plains area is largely mollisols now used for grain production.
Inceptisols
have a poorly developed A horizon, but no real B layer. This is because they form on relatively new surfaces (new river deposits, recently glaciated areas, volcanic ash, etc.). They form in areas with sufficient water to form the A horizon.
Entisols
have no horizons. This may be because there has not been sufficient time for horizons to develop (they are recent soils) or they are made of minerals that do not readily form horizons (like quartz sand on a sand dune). There may not be enough time for horizons to develop because of high erosion rates or it is a relatively new lava flow. can be found in any climatic region.
Soil structure
involves the clumping of individual soil particles to make larger particles
Pedogenic Regimes
is a fancy term for climate controlled soil forming systems. Pedology is soil science
Salinization
is common in desert soils with a high salt content. Salty water evaporates at the surface, leaving any salts in it behind.
Laterization
is common in tropical areas where there is very heavy rainfall. There is such intense leaching that most soil materials are removed, leaving a soil of mostly quartz sand and weathered iron and aluminum
Calcification
is found in drier regions. In arid areas, there is not enough water to carry the leached material to groundwater
Gleization
is found in poorly drained lands. In these areas, the organic matter is not decomposed
Podzolization
is found in the coniferous forests of the humid mid-latitudes
Soil color
is largely determined by the amount of organic matter and the amount and weathering of iron
fertility
of a soil is determined largely by the clay and humus present
Topography
of an area influences erosion and drainage
Gelisols
soils of periglacial areas. Freeze-thaw mixes up the soil, so horizons poorly developed. Slow decomposition, so much organic matter.
pH scale
where 7 is neutral (distilled water), less than 7 is acidic, and more than 7 is alkaline
Time
yet another factor determining what type of soil is present is