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