Why does volcanic ash make soil fertile?

Volcanic ash contributes to soil fertility because it is rich in nutrients. Over time, the decomposition of this nutrient-rich volcanic fallout enriches the soil, making it highly fertile.1

Volcanic ash is a type of parent material that influences soil formation through its mineralogical composition and texture. The specific minerals present in the ash, such as those containing iron and magnesium, can lead to soils with a high content of clay minerals. This composition, combined with the breakdown of volcanic materials, creates fertile soil conditions that support plant growth.21