Soils

Spodosol

a soil of an order rich in aluminum oxide and organic matter, typically characterized by low fertility, and including most podzols.

Alfisols

are moderately leached soils that have relatively high native fertility. These soils have mainly formed under forest and have a subsurface horizon in which clays have accumulated. Alfisols are primarily found in temperate humid and subhumid regions of the world. Alfisols occupy ~10.1% of the global ice-free land area. In the US, they account for ~13.9% of the land area. Alfisols support about 17% of the world's population. The combination of generally favorable climate and high native fertility allows Alfisols to be very productive soils for both agricultural and silvicultural use. Alfisols are divided into 5 suborders: Aqualfs, Cryalfs, Udalfs, Ustalfs, and Xeralfs. Click here for more information about these suborders

Entisols

are soils of recent origin. The central concept is soils developed in unconsolidated parent material with usually no genetic horizons except an A horizon. All soils that do not fit into one of the other 11 orders are Entisols. Thus, they are characterized by great diversity, both in environmental setting and land use. Many Entisols are found in steep, rocky settings. However, Entisols of large river valleys and associated shore deposits provide cropland and habitat for millions of people worldwide. Globally Entisols are the most extensive of the soil orders, occupying ~18% of the Earth's ice-free land area. In the US, Entisols occupy ~12.3% of the land area. Enttisols are divided into 6 suborders: Wassents, Aquents, Arents, Psamments, Fluvents, and Orthents

Batholiths

huge masses of granitic magmas that freeze into the crust

Soil

is that part of the regolith that supports plant life. It supports plant life out of doors (it has to be outside).

Organic Horizon

is the very top of the layer (recognizable plant parts)

Oxisol

mixture of three oxides, iron-oxide, silica-oxide, Aluminum oxide- no clay The extreme temperature and the climate the clay minerals break down very quickly. Living plants are living on the remains of the dead-they have roots that penetrate just the top of the soil.

Ag lime

neutralizes the soil and takes the acidic out of the soil

Aridosol

a soil of an order comprising typically saline or alkaline soils with very little organic matter, characteristic of arid regions.

E "eluviated"Horizon

"E", being short for eluviated, is most commonly used to label a horizon that has been significantly leached of clay, iron, and aluminum oxides, which leaves a concentration of resistant minerals, such as quartz, in the sand and silt sizes. These are present only in older, well-developed soils, and generally occur between the A and B horizons.The E horizon often has a pale color that is generally lighter in color than either the horizon above or below it. E horizons are commonly found in soils developed under forests, but are rare in soils developed under grasslands. In regions where this designation is not employed, leached layers are classified firstly as an A or B according to other characteristics, and then appended with the designation "e" (see the section below on horizon suffixes). In soils that contain gravels, due to animal bioturbation, a stonelayer commonly forms near or at the base of the E horizon. The above layers may be referred to collectively as the "solum". The layers below have no collective name but are distinct in that they are noticeably less affected by surface soil-forming processes.

Semi-arid

(Interior soils of the world) 10-20 inches

Histosols

(from Greek histos, "tissue") are soils that are composed mainly of organic materials. They contain at least 20-30% organic matter by weight and are more than 40 cm thick. Bulk densities are quite low, often less than 0.3 g cm3. Most Histosols form in settings such as wetlands where restricted drainage inhibits the decomposition of plant and animal remains, allowing these organic materials to accumulate over time. As a result, Histosols are ecologically important because of the large quantities of carbon they contain. These soils occupy ~1.2% of the ice-free land area globally and ~1.6% of the US. Histosols are often referred to as peats and mucks and have physical properties that restrict their use for engineering purposes. These include low weight-bearing capacity and subsidence when drained. They are mined for fuel and horticultural products. Histosols are divided into 5 suborders: Folists, Wassists, Fibrists, Saprists, and Hemists. Click here for more information about these suborders

Spodosols

(from Greek spodos, "wood ash") are acid soils characterized by a subsurface accumulation of humus that is complexed with Al and Fe. These photogenic soils typically form in coarse-textured parent material and have a light-colored E horizon overlying a reddish-brown spodic horizon. The process that forms these horizons is known as podzolization. Spodosols often occur under coniferous forest in cool, moist climates. Globally, they occupy ~4% of the ice-free land area. In the US, they occupy ~3.5% of the land area. Many Spodosols support forest. Because they are naturally infertile, Spodosols require additions of lime in order to be productive agriculturally. Spodosols are divided into 5 suborders: Aquods, Gelods, Cryods, Humods, and Orthods. Click here for more information about these suborders.

Andisols

(from Japanese ando, "black soil") are soils that have formed in volcanic ash or other volcanic ejecta. They differ from those of other orders in that they typically are dominated by glass and short-range-order colloidal weathering products such as allophane, imogolite, and ferrihydrite. As a result, Andisols have andic properties - unique chemical and physical properties that include high water-holding capacity and the ability to 'fix' (and make unavailable to plants) large quantities of phosphorus. Globally, Andisols are the least extensive soil order and only account for ~1% of the ice-free land area. They occupy ~1.7% of the US land area, including some very productive forests in the Pacific Northwest region. Andisols are divided into 8 suborders: Aquands, Gelands, Cryands, Torrands, Xerands, Vitrands, Ustands, and Udands.

Gelisols

(from Latin gelare, "to freeze") are soils of very cold climates that contain permafrost within 2 meters of the surface. These soils are limited geographically to the high-latitude polar regions and localized areas at high mountain elevations. Because of the extreme environment in which they are found, Gelisols support only ~0.4% of the world's population - the lowest percentage of any of the soil orders. Gelisols are estimated to occupy ~9.1% of the Earth's ice-free land area and ~8.7% of the US. Although some Gelisols may occur on very old land surfaces, they show relatively little morphological development. Low soil temperatures cause soil-forming processes such as decomposition of organic materials to proceed very slowly. As a result, most Gelisols store large quantities of organic carbon - only soils of wetland ecosystems contain more organic matter. Gelisols of the dry valleys of Antarctica are an exception - they occur in a desert environment with no plants and consequently contain very low quantities of organic carbon. The frozen condition of Gelisol landscapes makes them sensitive to human activities. Gelisols are divided into 3 suborders: Histels, Turbels, and Orthels

Inceptisols

(from Latin inceptum, "beginning") are soils that exhibit minimal horizon development. They are more developed than Entisols, but still lack the features that are characteristic of other soil orders. Although not found under aridic climate regimes, Inceptisols nevertheless are widely distributed and occur across a wide range of ecological settings.They are often found on fairly steep slopes, young geomorphic surfaces, and on resistant parent materials. Land use varies considerably with Inceptisols. A sizable percentage of Inceptisols are found in mountainous areas and are used for forestry, recreation, and watershed. Inceptisols occupy an estimated 15% of the global ice-free land area - only the Entisols are more extensive. In the US, they occupy ~9.7% of the land area. Inceptisols support ~20% of the world's population, the largest percentage of any of the soil orders. Inceptisols are divided into 7 suborders: Aquepts, Anthrepts, Gelepts, Cryepts, Ustepts, Xerepts, and Udepts.

Mollisols

(from Latin mollis, "soft") are the soils of grassland ecosystems. They are characterized by a thick, dark surface horizon. This fertile surface horizon, known as a mollic epipedon, results from the long-term addition of organic materials derived from plant roots. Mollisols primarily occur in the middle latitudes and are extensive in prairie regions such as the Great Plains of the US. Globally, they occupy ~7.0% of the ice-free land area. In the US, they are the most extensive soil order, accounting for ~21.5% of the land area. Mollisols are among some of the most important and productive agricultural soils in the world and are extensively used for this purpose. Mollisols are divided into 8 suborders: Albolls, Aquolls, Rendolls, Gelolls, Cryolls, Xerolls, Ustolls, and Udolls.

Ultisols

(from Latin ultimus, "last") are strongly leached, acid forest soils with relatively low native fertility. They are found primarily in humid temperate and tropical areas of the world, typically on older, stable landscapes. Intense weathering of primary minerals has occurred, and much Ca, Mg, and K has been leached from these soils. Ultisols have a subsurface horizon in which clays have accumulated, often with strong yellowish or reddish colors resulting from the presence of Fe oxides. The 'red clay' soils of the southeastern United States are examples of Ultisols. Ultisols occupy ~8.1% of the global ice-free land area and support 18% of the world's population. They are the dominant soils of much of the southeastern US and occupy ~9.2% of the total US land area. Because of the favorable climate regimes in which they are typically found, Ultisols often support productive forests. The high acidity and relatively low quantities of plant-available Ca, Mg, and K associated with most Ultisols make them poorly suited for continuous agriculture without the use of fertilizer and lime. With these inputs, however, Ultisols can be very productive. Ultisols are divided into 5 suborders: Aquults, Humults, Udults, Ustults, and Xerults. Click here for more information about these suborders

C horizon

Also called regolith: the layer beneath the B Horizon and above the R Horizon. It consists of slightly broken-up bedrock. Plant roots do not penetrate into this layer; very little organic material is found in this layer.

B horizon

B horizons form below an O, A, or E horizon and they have undergone sufficient changes during soil genesis, such that the properties of their original parent material are no longer discernible. The B horizon is commonly referred to as the "subsoil". In humid regions, B horizons are the layers of maximum accumulation of materials such as silicate clays, iron (Fe) and aluminum (Al) oxides, and organic material. These materials typically accumulate through a process termed illuviation, wherein the materials gradually wash in from the overlying horizons. Accordingly, this layer is also referred to as the "illuviated" horizon or the "zone of accumulation". In addition, it is defined as having a distinctly different structure or consistency than the horizon(s) above and the horizon(s) below. The B horizon may also have stronger colors (higher chroma) than the A horizon. In arid and semiarid regions, calcium carbonate or calcium sulfate may accumulate in the B horizon.

Forest soil greater than 20 inches of precipitation

Spodosol & Ultisol

A Horizon

The A horizon is the topmost mineral horizon, often referred to as the 'topsoil'. This layer generally contains enough partially decomposed (humified) organic matter to give the soil a color darker than that of the lower horizons.The A horizons are often coarser in texture, having lost some of the finer materials by translocation to lower horizons and by erosion. This layer is known as the zone in which the most biological activity occurs. Soil organisms such as earthworms, potworms (enchytraeids), arthropods, nematodes, fungi, and many species of bacteria and archaea are concentrated here, often in close association with plant roots. Thus the A horizon may be referred to as the biomantle. However, since biological activity extends far deeper into the soil, it cannot be used as a chief distinguishing feature of an A horizon.

R Horizon

The unweathered rock (bedrock) layer that is beneath all the other layers.

Ultisol

a highly weathered leached red or reddish-yellow acid soil with a clay-rich B horizon (subsoil), occurring in warm, humid climates.

Mollisol:

a soil of an order comprising temperate grassland soils with a dark, humus-rich surface layer containing high concentrations of calcium and magnesium.

Talus

rock waste from crystals growing due to the presence of ground water.

Exfoliation

sheets of rock that sloughs off of the rocks.

Co-efficient of thermal expansion

the change in length or area of a material per unit length or unit area that accompanies a change in temperature of one degree

Efflorescence

the growth of crystals just beneath the surface of the rock.