Andisols (from the Japanese ando – black soil) typically form from the weathering of volcanic materials such as ash, resulting in minerals in the soil with poor crystal structure. These minerals have an unusually high capacity to hold both nutrients and water, making these soils very productive and fertile.
Andisols include weakly weathered soils with much volcanic glass, as well as more strongly weathered soils.
They typically occur in areas with moderate to high rainfall and cool temperatures. They also tend to be highly erodible when on slopes.
These soils make up about 1% of the glacier-free land surface.