University of Idaho College of Agricultural and Life Sciences Plant, Soil & Entomological Sciences Soil & Land Resources
Soil Orders
Soil Links
  Gelisols    Histosols    Spodosols    Andisols    Oxisols    Vertisols    Aridisols    Ultisols    Mollisols    Alfisols    Inceptisols    Entisols


Andisols (from Japanese ando, "black soil") are soils that have formed in volcanic ash or other volcanic ejecta. They differ from those of other orders in that they typically are dominated by glass and short-range-order colloidal weathering products such as allophane, imogolite, and ferrihydrite. As a result, Andisols have andic properties - unique chemical and physical properties that include high water-holding capacity and the ability to 'fix' (and make unavailable to plants) large quantities of phosphorus.

Globally, Andisols are the least extensive soil order and only account for ~1% of the ice-free land area. They occupy ~1.7% of the US land area, including some very productive forests in the Pacific Northwest region.

Andisols are divided into 8 suborders: Aquands, Gelands, Cryands, Torrands, Xerands, Vitrands, Ustands, and Udands. Click here for more information about these suborders. Click here to view a map of their distribution in the US.

Click on map to view larger image

Click on map to view larger image
<< back to Soil Orders list example 1 >> 
1. Udivitrand landscape
New Zealand

2. Udivitrand
New Zealand

3. Melanudand landscape
Costa Rica
4. Melanudand
Costa Rica
5. Vitrixerand landscape
northern Idaho
6. Volcanic ash
from Mt. Mazama Oregon
7. Typic Vitrixerand
northern Idaho
8. eroded Cryand landscape
9. Cryand
If you have any comments, suggestions, or questions about the 12 Soil Orders web site,
please contact
  Dr. Paul McDaniel  at the Soil Science Division,
University of Idaho, Moscow, ID 83844-2339.