Volcanic soils are often associated with savory, ash-driven wines from areas with active volcanoes, like Sicily, the Canary Islands and beyond. However, viticultural regions across the globe have these soils, and their compositions and resulting flavor profiles vary.
According to geologist Brenna Quigley, volcanic soils are any that form directly from the weathering of volcanic rocks, otherwise known as “extrusive igneous” rocks.
“Volcanic soils and terroirs can actually be highly variable from one another depending on their chemistry and climatic setting,” she says. “But, overall, volcanic terroirs tend to be relatively young and produce shallow, acidic soils.”
Basaltic terroirs make up a significant portion of global volcanic terroirs, Quigley adds, and are dark red to black in color, fertile and heat retentive, with slightly acidic pHs. Regions with basaltic terroirs include Mount Etna, the Willamette Valley, the Canary Islands and Australia’s Yarra Valley.
Ian Burch, the winemaker for Archery Summit in Willamette, Oregon, cultivates vines in Jory soil, a type of volcanic soil that consists of broken-down basalt. “This clay loam has a very high affinity to water and macro- and micronutrients, which are essential to plant growth,” he says.
Volcanic soils make up Intermediate and Felsic terroirs. Born from extremely violent eruptions, these soils are not as consistent as basaltic soils. “These terroirs include terms such as andesite, rhyolite, tuff and obsidian, and are found in Napa and Sonoma valleys, Alsace, Tokaj and Santorini,” he says.
While volcanic soils in global regions like Tenerife, Spain can be more than three million years old, the majority of volcanic soils on the West Coast of the United States are actually quite young compared to other soil types, says Marc Gagnon, winemaker at Bryant Family Vineyard and Gagnon-Kennedy Vineyards. Gagnon adds that U.S. volcanic soils are typically high in iron.
So, what does this mean in terms of cultivation? Geoffrey Cohen, sales manager at Domaine Montrose in the Languedoc region of Southern France, says that the estate’s well-draining volcanic soils create excellent conditions for cultivating vines. Cohen believes these soils lead to lower yields and more concentration and body in the final wines produced.
Lewis Kopman, cofounder of GK Selections, notes that volcanic soils’ excellent drainage makes the vines grown in them less susceptible to phylloxera. It leads to “unprecedented concentration” in grapes.
“Concentrated grapes are not necessarily ripe or fruity ones, rather, that there is less water relative to the other molecules in each grape,” says Kopman. “This means that acidity also gets concentrated, and in cooler volcanic climates such as Portugal’s Azores Islands, you get an unrivaled concentration of acidic compounds and mineral flavors.”
Wines made from grapes grown in volcanic soils can have varied and complex flavor profiles. The amount of iron and potassium in many volcanic soils can lend a “salty sweetness” to the resulting wines, Burch says, and Pinot Noir from areas with iron-rich, clay volcanic soil tends to be quite elegant.
Benjamin Spencer, winemaker and author of The New Wines of Mount Etna, believes that volcanic soils can contribute an “exciting tension, edginess and savory quality” to the wines they produce. “A lot of people brand this sensation in the mouth as minerality, but it is a wine’s reflection of the abundance of stone, metal and nutrients in the soil,” he says.
Gagnon finds that volcanic soils provide “great[er] aromatic attributes and fruit purity than other soils, while also not introducing too much phenolic dryness” and lead to an overall supple and mouthwatering finish.
However, the connections between soil type and wine flavors or aromas are complex. “It seems like the sites that express distinct, smoky aromas are on or very near to a truly active volcano,” says Quigley. It’s even possible there’s some remnant of volcanic ash in the air or within the soil that gets incorporated into the wine, she says, but notes that she doesn’t have any specific research on the subject.
“As with looking at the expression of most terroirs, it’s useful to look at the specifics of the parent material,” she says. When considering how volcanic soil impacts wine, it’s important to ask what kind of volcanic rock is present, how evolved the soil profile is and how deep the soils extend beneath the outer surface. It’s also useful to consider how rocky, sandy or clay-rich the soils are and their climate.
“All of these factors will influence the taste of the wine and its potential to express volcanic qualities,” says Quigley.