Soil & Science Exam 2

The 12 Soil Order

Entisols- soils that have little or no horizon development 

Inceptisols- some horizon development 

Andisols-soils recently formed in volcanic materials

Histosols- organic soils

Gelisols - cold conditions, permafrost

Aridisols - dry climate, desert vegetation

Vertisols - swelling clays

Alfisols - mildly acid, forest soils

Mollisols - dark, soft, prairie soils

Spodosols - sandy, acid, coniferous forest soils

Ultisols - strongly acid, high clay and iron oxides 

Oxisols - highly weathered, strongly acid,



Entisols (-ent)

*name comes from Recent

*little or no horizon 

* soils are recently formed in areas

  • Recent alluvium

  • Lava flows

  • Desert regions

  • Steep slopes 

Located: Scattered around in areas where lost of disturbance or dry

12% covered in the US - the rockies, dry areas, sandy soil



Inceptisols (-ept)

* Will be able to describe some b horizon 



  • From inception

  • Beginning of soil profile development 

  • Have a ochric epipedon 

  • Cambic subsurface, no argillic or kandic horizon

Located: covers about 10% of the global land, more prominent in mountains areas, more colder areas

9% in the US - Appalachian , Northeast, west coast areas

Andisols (-and)

  • Volcanic materials 

  • Form in volcanic ash and cinders 

  • Not highly weathered

  • Light and fluffy soils 

  • High natural fertility 

  • Characterized by poorly crystalline minerals

  • Can be detected by pH test- very alkaline 

Located: less than 1% that will be classified as andisols

Northwest of the US- most recent volcanic eruptions (Hawaii) ½% total land in the US



Gelisols (-el)

  • Permafrost Layer

  • Features of cryoturbation, or frost

  • Young soils w/ little profile development

  • Not a lot of weathering 

  • Construction Nightmare 



Located: 8 ½% globally Northern Canada, Russia, Himalayas 

8.5 % in the US = Alaska 



Histosols (-ist)

  • Organic material in more than half of the upper 80cm of soil

  • Undergone little profile development

  • Found in marshes, bogs, and swamps 



Located: little over 1.2 % russia, scandinavia, northern UK/Scotland 

US- little over 1% down in florida (everglads) 



Aridisols (-id)

  • Aridic moisture regime (DRY!)

  • Ochric epipedion light in color and low in organic matter 

  • Accumulations of soluble salts, calcium, carbonate

  • Main land use is rangeland 



Located: 12% globally,Southwestern area rocky areas 8-9% US soils 



Vertisols (-ert)



  • Characterized by having clays with high shrink-swell capacity 

  • Clay-rich soils that shrink

  • >30% clay to a depth of 1m of more

  • Under grassland 

  • Develop from limestone, basalt, and other

  • Soils are dark (sometimes almost black)

  • Dark color is NOT indicative of organic matter!

  • Often form large cracks on the surface when dry

  • Overtime will develop gilgai features 

Located: 2.5 % globally a bit in india and eastern australia

US: Texas, Louisiana- little under 2% fit in this soil order 

  • Not GOOD for building on 



Mollisols (-oll) 

  • Main soil forming process 

  • Most have developed under grassland vegetation 

  • Dominant soils of great plains 

  • Characteries by a deep dark, A Horizon- lots of this!!!

  • Dark Color

Located: Globally 7% ; Europe- Ukraine, Russia, 

US: 25% will be classified as this soil 

Illinois - Drummer silt loam 



Alfisols (-alf)

  • Form under native forest vegetation 

  • Have a subsurface horizon w/clay accumulation

  • Argillic, Natric, or Kandic Horizon 

  • Ochric epipedon

  • Greater than 35%

  • Very fertile

Located:  Globally 10% - Different types of climates

Iowa and Illinois - prairie

US- 15% will be classified as this soil particularly the midwest



Ultisols (ult) 

  • Develop under warm conditions in warm, tropical climates, forest vegetation

  • Highly weathered minerals than Alfisols

  • Subsurface horizons are usually RED or YELLOW

  • Iron Oxides

  • Some contain Plinthite-iron rich mottled horizon 

Located: 9% globally 

US- Southeastern Area 

Spodosols (-od)

  • On sandy parent material 

  • Intensive acid leaching 

  • Spodic subsurface horizon

  • Subsurface accumulation of organic matter and accumulation Al and Fe oxides

  • Spodic Horizon usually lies below a light colored albic horizon 

Located: scandinavia, russia, canada - 2.6% globally

US- northern wisconsin, michigan, maine, northern new york 

Oxisols (-ox)

  • Highly weathered soils

  • Hot Climates with year-round moisture

  • Orchic or umbric epipedons

  • Deep, oxic subsurface horizon 

  • High in ‘low activity” clay

  • High in Fe- and AI oxides

Located: South American, Southern Africa - 8%

US: Hawaii/Puerto Rico -