Mollisols (from the Latin mollis – soft) are prairie or grassland soils that have a dark-colored surface horizon. They are highly fertile and rich in chemical “bases” such as calcium and magnesium.
The dark surface horizon comes from the yearly addition of organic matter to the soil from the deep roots of prairie plants.
Mollisols are often found in climates with pronounced dry seasons. They make up approximately 7% of the glacier-free land surface.