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In USDA soil taxonomy, entisols are defined as soils that do not show any profile development other than an A horizon. An entisol has no diagnostic horizons, and most are basically unaltered from their parent material, which can be unconsolidated sediment or rock. Entisols are the second most abundant soil order (after inceptisols), occupying about 16% of the global ice-free land area. 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 (e.g. ''fluvisols'', ''lithosols''). == 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 flood as diluvium, aeolian processes which means by wind, slope processes as colluvium, mudflows, other means. * Flooding or saturation. * Cold climate - must not be sufficiently cold in winter for permafrost. * Dry climate. * Shallow to bedrock - may be rock resistant to weathering, such as quartzite or ironstone. * Toxic parent materials - serpentine soil, mine spoils, sulfidic clays. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「entisol」の詳細全文を読む スポンサード リンク
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