There is much debate in the world of wine about the impact that soil has on wine. Soil types differ by the size of particles, mineral and nutrient content, amount of decomposed organic material, and water retention capacity. Volcanic soils are different as they can be formed by a variety of events like slow flowing lava, explosively expelled rock, and airborne ash that settles to form a new layer.
Soil types include jet-black basalt, pumice, and volcanic alluvium that settles into valleys. Features common to volcanic soils include a wide range of mineral content, a good balance of those minerals, low quantity of organic material, generally low water retention, and low fertility. These types of soils represent only about 1% of the total surface on the planet.
Grapes grown in volcanic soils are relatively small and usually high in acidity, with low ripeness. Small berry size means that the grapes have more concentrated flavors. Low ripeness means that the wines made from these grapes may display more savory flavors as opposed to fruitiness. Grapes grown on volcanic soils yield wines that often have salinity as one of their characters.
Volcanic soil is porous which means that water flows over the roots of the vine quickly. Since the roots are in contact with the water for only a short period of time, the roots dig deeper in search of a better water supply. Because the vines work harder as they search for water, the wines produced have more intense flavors, more tannin, and mineral notes to them.
Regions with volcanic soils are locations with mountains and that means that altitude, slope, and orientation of the sun also contribute heavily to the wines produced. These regions are often in remote areas, with rugged terrain, which means that the grapes must be harvested by hand.
If you are interested in trying wines made from grapes grown on volcanic soil, look for labels from Mount Etna, Sicily; Santorini, Greece; Somlo, Hungary; the island of Sardinia, Italy; The Azores, Portugal; The Canary Islands, Spain; Campania, Italy; Soave, Italy; Golan Heights, Israel; Madeira; and Lake County, California.