In more acidic tephras in humid climates, complexes of organic matter with Al ions develop, and the Andosols are characterized by the Aluandic qualifier.

If the tephras are more basic or the climate is dry, amorphous colloidal materials, including allophane and imogolite develop, and the Andosols are given the Silandic qualifier.

[6] Silandic Andosols are very fertile except in cases where phosphorus is easily fixed (this sometimes occurs in the tropics).

Other Andosol areas support crops of fruit, maize, tea, coffee or tobacco.

[7] Fossil Andosols are known from areas far from present-day volcanic activity and have in some cases been dated as far back as the Precambrian 1.5 billion years ago.