🪨 Volcanic soil

Volcanic soil (also volcanic terroir) is earth formed from weathered volcanic rock: cooled lava, basalt, compacted ash called tuff. Grapes grow on it on Santorini in Greece and on Pico Island in the Azores, among other places. Scientists speak more cautiously than winemakers about what it does to taste.

The most striking example is the vineyard culture of Pico Island, a UNESCO site. On this volcanic island, the second largest in the Azores, long walls of local black basalt run inland. They shelter thousands of small rectangular plots (currais) from wind and seawater across 987 hectares. Vines are planted in nearly soilless cells, and the tradition goes back to the 15th century. The small lava-flow fields of Criação Velha and Santa Luzia are especially valued.

On Santorini the Assyrtiko grape is known for its volcanic terroir, low pH and sharp acidity, researchers write in Microorganisms (2024).

Then there is that word, minerality. A 2018 OENO One review reminds us that evidence for soil minerals as main drivers of terroir is thin. Talk of deep roots collecting trace elements has never been explained in terms of aroma. What is known is that volcanic rocks hold a lot of potassium, and an excess can raise the pH of must and wine.

So a volcano taste is more an impression than proven chemistry. For the rocks themselves see basalt and tuff, and for the broader theme see soil. By contrast, the white chalky albariza of Jerez is a different world.