Entisol
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In USA soil taxonomy, Entisols are defined as soils that do not show any profile development. An Entisol has no diagnostic horizons, and most are basically unaltered from their parent rock.
In Australia, most Entisols are known as Rudosols or Tenosols, whilst Arents are known as Anthroposols. In the FAO soil classification, because of the diversity of their properties, suborders of Entisols form individual soil orders (eg. Fluvisols, Lithosols).
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[edit] Causes of delayed or absent development:
- Unweatherable parent materials - sand, iron oxide, aluminium oxide, kaolinite clay.
- Erosion - common on shoulder slopes; other kinds also important.
- Deposition - continuous, repeated deposition of new parent materials by water, wind, colluvium, mudflows, other means.
- Flooding or saturation.
- Cold climate - must not be suffiently cold in winter for permafrost.
- Dry climate.
- Shallow to bedrock - may be "unweatherable" rock such as quartzite or ironstone.
- Toxic parent materials - serpentinite, mine spoils, sulfidic clays.
[edit] Suborders:
- Aquents - permentantly or usually wet soils formed on river banks, tidal mudflats etc. Here, general wetness limits development.
- Arents - anthropogenic soils: diagnostic horizons cannot develop because of deep mixing through plowing, spading, or other methods of moving by humans.
- Fluvents - alluvial soils where development is prevented by repeated deposition of sediment in periodic floods. Found in valleys and deltas of rivers, especially those with high sediment load.
- Orthents - shallow or "skeletal soils". Found on recent erosional surfaces or very old landforms completely devoid of weatherable minerals.
- Psamments - Entisols that are sandy in all layers where development is precluded by the impossibility of weathering the sand. Formed from shifting or glacial sand dunes.
[edit] Paleopedology
Most fossil soils before the development of terrestrial vegetation in the Silurian are Entisols, showing no distinct soil horizons. Entisols have been abundant in the paleopedological record ever since then, though, unlike other soil orders (Oxisols, Ultisols, Gelisols for instance) they do not have value as indicators of climate - though Orthents might in some cases be indicated of an extremely old landscape with very little soil formation (as in Australia today).
