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Definition
mineral surface horizon noted for its dark color which comes from accumulated organic matter. it is very thick and soft, with a base saturation >50%. developed under grassland. |
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Definition
Same general characteristics as a mollic epipedon, except base saturation is lower (mollic's is >50%). It commonly develops in areas that receive more rainfall, and where the parent material has a lower content of Calcium and Magnesium.
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Mineral horizon that is too thin, too light in color, or too low in organic matter to be either mollic or umbric. May be hard and massive when dry.
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Black, organic-matter-rich mineral horizon characteristic of soils developed from volcanic ash. It is >30cm thick and extremely lightweight/fluffy for a mineral soil.
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| 20-60cm thick layer of organic soil materias overlying a mineral soil. It is formed in wet areas and is a layer of black to dark brown peat or muck with a very low density. |
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| Subsurface accumulation of high-activity silicate clays that have moved downward from upper horizons or have formed in place. |
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| Subsurface horizon with silicate clay accumulation and >15% exchangeable sodium on the colloidal complex. Has columnar or prismatic structural units. Found mostly in arid and semiarid areas. |
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Definition
| Subsurface horizon featuring an accumulation of Fe and Al oxides as well as low-activity silicate clays (i.e. kaolinite). Doesn't necessarily require evidence of clay skins. The clays are low in activity as shown by their low cation-holding capacities. The epipedon that overlies this horizon has commonly lost much of its clay content. |
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Term
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Definition
| Highly-weathered subsurface horizon that is very high in Fe and Al oxides, and in low-activity silicate clays (i.e. kaolinite). Low cation-holding capacity. This horizon is >30cm thick and has <10% weatherable minerals. Generally physically stable, crumbly, and not very sticky despite high clay content. Found mostly in humid tropical and subtropical regions. |
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Term
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Definition
Illuvial horizon that is characterized by the accumulation of colloidal organic matter and Al oxide (can be with or without Fe oxide). Commonly found in highly leached forest soils of cool humid climates, typically on sandy-textured parent materials.
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Term
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Definition
Illuvial horizon, dark in color because of high organic matter accumulation. Has a low degree of base saturation and is found mostly in the cool, moist soils of high plateaus and mountains in tropical and subtropical regions.
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Term
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Definition
Light-colored eluvial horizon that is low in clay and oxides of Fe and Al. These materials have largely been moved downward from this horizon.
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| Subsurface horizon that contains an accumulation of carbonates (mostly CaCO3) that often appear as white chalklike nodules. AKA Bk horizon. |
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Term
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Definition
Subsurface horizon characterized by an accumulation of soluble salts.
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Definition
| Subsurface horizon featuring an accumulation of gypsum (type of salt) [CaSO4 x 2H2O]. |
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Term
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Definition
Presence of albic horizon (bleached eluvial horizon).
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Term
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Definition
Presence of anthropic or plaggen epipedon.
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Definition
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| Mixed horizons. (From Latin arare... to plow). |
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Definition
Presence of argillic horizon (horizon with illuvial clay).
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Definition
Presence of calcic horizon (accumulation of carbonates).
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Definition
| Presence of cambic horizon. |
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Definition
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Definition
Presence of a duripan (hard).
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Definition
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Definition
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Definition
Presence of gypsic horizon (accumulation of gypsum salts).
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Term
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Definition
Intermediate stage of decomposition.
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Term
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Definition
Presence of organic matter.
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Term
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Definition
Presence of organic matter.
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| The common ones (from Latin orthos, true). |
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Definition
Of year-round humid climates, perudic moisture regime.
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| Rendzinalike- high in carbonates. |
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Definition
Presence of salic (saline) horizon.
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Of dry climates, usually hot in summer.
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| Dry summers, moist winters (Mediterranean). |
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Definition
Surface diagnostic horizon A, E, and sometimes part of B horizon |
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Term
Subsurface diagnostic horizons
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