Entisols are

soils Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by restri ...

, as defined under

USDA soil taxonomy USDA soil taxonomy (ST) developed by the United States Department of Agriculture and the National Cooperative Soil Survey provides an elaborate Soil classification, classification of soil types according to several parameters (most commonly their p ...

, that do not show any profile development other than an A-horizon (or “A” horizon). Entisols have no diagnostic horizons, and are unaltered from their parent material, which could be unconsolidated sediment, or rock. Entisols are the most common soils, occupying about 16% of the global ice-free land area. Because of the diversity of their properties, suborders of entisols form individual Reference Soil Groups in the ''

World Reference Base for Soil Resources The World Reference Base for Soil Resources (WRB) is an international soil classification system for naming soils and creating legends for soil maps. The currently valid version is the fourth edition 2022. It is edited by a working group of the I ...

'' (WRB):

psamment In USDA soil taxonomy, a Psamment is defined as an Entisol which consists basically of unconsolidated sand deposits,arenosol In USDA soil taxonomy, a Psamment is defined as an Entisol which consists basically of unconsolidated sand deposits,fluvent Entisols are soils, as defined under USDA soil taxonomy, that do not show any profile development other than an A-horizon (or “A” horizon). Entisols have no diagnostic horizons, and are unaltered from their parent material, which could ...

s with

fluvisol A fluvisol in the World Reference Base for Soil Resources (WRB) is a genetically young soil in alluvial deposits . Apart from river sediments, they also occur in lacustrine and marine deposits. Fluvisols correlate with fluvents and fluvaquents ...

s. Many

orthent Orthents are soils defined in USDA soil taxonomy as entisols that lack due to either steep slopes or parent materials that contain no permanent weatherable minerals (such as ironstone). Typically, Orthents are exceedingly shallow soils. They ...

s belong to

regosol A Regosol in the World Reference Base for Soil Resources (WRB) is very weakly developed mineral soil in Soil consolidation, unconsolidated materials. Regosols are extensive in erosion, eroding lands, in particular in arid and semi-arid areas and i ...

s or

leptosol A Leptosol in the World Reference Base for Soil Resources (WRB) is a very shallow soil over continuous rock or a deeper soil that is extremely rich in coarse fragments (gravelly and/or stony). Leptosols cover approximately 1.7 billion hectares o ...

s. Most ''wassents'' and aquic subgroups of other suborders belong to the

gleysol A gleysol or gley soil is a hydric soil that unless drained is saturated with groundwater for long enough to develop a characteristic colour pattern. The pattern is essentially made up of reddish, brownish, or yellowish colours at surfaces of so ...

s. In

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

, most entisols are known as rudosols or tenosols.

Causes of delayed or absent development

* Unweatherable parent materials –

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

oxide, kaolinite

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

. * Erosion – common on shoulder

slopes In mathematics, the slope or gradient of a Line (mathematics), line is a number that describes the direction (geometry), direction of the line on a plane (geometry), plane. Often denoted by the letter ''m'', slope is calculated as the ratio of t ...

; other kinds also important. * Deposition – continuous, repeated deposition of new parent materials by flood as

diluvium Diluvium is an archaic term applied during the 1800s to widespread surficial deposits of sediments that could not be explained by the historic action of rivers and seas. Diluvium was initially argued to have been deposited by the action of extra ...

aeolian processes Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erosion, erode, transport, and deposit ...

which means by

wind Wind is the natural movement of atmosphere of Earth, air or other gases relative to a planetary surface, planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heatin ...

, slope processes as

colluvium Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediments that have been deposited at the base of hillslopes by either rainwash, Sheet erosion , sheetwash, slow continuous downslope creep, or a va ...

mudflow A mudflow, also known as mudslide or mud flow, is a form of mass wasting involving fast-moving flow of debris and dirt that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/se ...

s, other means. * Flooding or saturation. * Cold climate – must not be sufficiently cold in winter for

permafrost Permafrost () is soil or underwater sediment which continuously remains below for two years or more; the oldest permafrost has been continuously frozen for around 700,000 years. Whilst the shallowest permafrost has a vertical extent of below ...

. * Dry climate. * Shallow to bedrock – may be rock resistant to

weathering Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...

, such as

quartzite Quartzite is a hard, non- foliated metamorphic rock that was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tecton ...

ironstone Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially. Not to be c ...

. * Toxic parent materials –

serpentine soil Serpentine soil is an uncommon soil type produced by weathered ultramafic rock such as peridotite and its metamorphic derivatives such as serpentinite. More precisely, serpentine soil contains minerals of the serpentine subgroup, especially an ...

, mine spoils,

sulfidic Sulfidation (British spelling also sulphidation) is a process of installing sulfide ions in a material or molecule. The process is widely used to convert oxides to sulfides but is also related to corrosion and surface modification. Inorganic, mate ...

clays.

Suborders

Aquent Aquent is a staffing company specializing in placing temporary employees in marketing and creative industries. According to Staffing Industry Analysts, it is among the "largest marketing/creative staffing firms in the United States". Aquent also o ...

s – heavily saturated or soaked soils, mostly present at

riparian A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripar ...

locations (such as river banks, tidal

mudflats Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal ...

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

, etc). Here, consistent saturation limits development. *Fluvents – alluvial soils, where development is prevented by repeated deposition of

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

during periodic

flooding A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant concern in agriculture, civi ...

events; present in

valleys A valley is an elongated low area often running between hills or mountains and typically containing a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over a ve ...

river deltas A river delta is a landform, wikt:archetype#Noun, archetypically triangular, created by the deposition (geology), deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or ...

, especially those with high sediment load. *

Orthent Orthents are soils defined in USDA soil taxonomy as entisols that lack due to either steep slopes or parent materials that contain no permanent weatherable minerals (such as ironstone). Typically, Orthents are exceedingly shallow soils. They ...

s – shallow or "skeletal" soils; found at sites of recent

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

events, or very old landforms ''completely devoid of weatherable

minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): M ...

''. *

Psamment In USDA soil taxonomy, a Psamment is defined as an Entisol which consists basically of unconsolidated sand deposits,glacial A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

sand dunes A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, flat ...

. *Wassents – Entisols that have a positive water potential at the soil surface for more than 21 hours of each day, in all years.

Paleopedology

Most

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

soils, before the development of terrestrial vegetation in the

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...

, are entisols that show no distinct soil horizons. Entisols are common in the

paleopedological record {{inline citations, date=June 2013 The paleopedological record is, essentially, the fossil record of soils. The paleopedological record consists chiefly of paleosols buried by flood sediments, or preserved at geological unconformities, especially ...

ever since the Silurian; however, unlike other soil orders (

oxisol Oxisols are a soil order in USDA soil taxonomy, best known for their occurrence in tropical rain forest within 25 degrees north and south of the Equator. In the World Reference Base for Soil Resources (WRB), they belong mainly to the ferrals ...

ultisol Ultisol, commonly known as red clay soil, is one of twelve soil orders in the USDA soil taxonomy, United States Department of Agriculture soil taxonomy. The word "Ultisol" is derived from "ultimate", because Ultisols were seen as the ultimate pr ...

gelisol Gelisols are an order in USDA soil taxonomy. They are soils of very cold climates which are defined as containing permafrost within of the soil surface. The word "Gelisol" comes from the Latin meaning "to freeze", a reference to the proce ...

, etc) they do not have value as indicators of climate. Orthents may sometimes indicate an extremely ancient landscape with minimal soil formation (i.e., Australia today).

References

* * * {{Soil type Pedology Types of soil

Causes of delayed or absent development

Suborders

Paleopedology

See also

References