Terroir is more than just a buzzword these days. Across Argentina and Chile (and many other parts of the globe) winemakers have increasingly shifted their focus toward wines that express a unique sense of place. But understanding true terroir requires a deeper understanding of what’s secreted beneath the earth’s surface—and expertise that goes well beyond what’s taught in most viticultural programs.
To fill in those knowledge gaps, many producers have turned to geologists.
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“Geologists specialize in studying soils and their evolution,” says geologist Eder González, who has been working with wineries across Chile since 2010. Though these scientists “don’t tell winemakers what, how or where to plant vines,” oftentimes, winemakers and growers make key planting decisions based on their findings. “We can provide detailed insights into how the geology, rocks and hills surrounding their vineyards have evolved.”
Such knowledge has translated to a growing number of single-vineyard labels, which hail from geologist-identified sites able to produce wines with distinctive characteristics. The influence of geologists, many argue, is changing the game for Chilean and Argentinian wineries, helping them reach new levels of excellence and sustainability.
The Secret’s in the Soil
Geologists’ central mission is to segment and classify vineyards. They harness a plethora of lab tests, soil pits and other tools to do so, singling out layers of sediment, rock and other geological features.
For example, Gonzalez explains, he might want to know why the clay content differs in two different plots of land, despite having the same bedrock, or why some rivers created alluvial terraces while others did not.
In some cases, these surveys have prompted the development of new wine regions. One example is Limarí Valley in northern Chile, where Gonzalez and other experts studied the abundance of limestone soils in some areas. This soil type is associated with desirable characteristics in wine, such as vibrancy and mineral texture. Limarí Valley is now recognized as one of the world’s top regions for white wines, with prominent producers such as Viña Santa Rita and Concha y Toro sourcing Chardonnay and Sauvignon Blanc from it.
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Geologists are also helping the continent’s more well-established destinations grow further afield. In Mendoza, Argentina, the expansion of vineyards from the lowlands in the east to the higher altitude regions of Luján de Cuyo and the Uco Valley, which began about 30 years ago, was driven by wineries’ search for cooler temperatures. But the move brought new challenges and opportunities for professionals like geophysicist Guillermo Corona, creator of the Instagram account @geografiadelvino and author of the book Geografía del Vino.
“As winemakers moved closer to the mountains, they encountered more stony and heterogeneous soils,” Corona says. Over the last decade, his geology research helped many wineries pinpoint the best sites to grow grapes. “If someone wants to find the best place to plant vines, and within that place, find the best patchwork of land, then they need to study the soil,” he says.
A New Approach to Winemaking
The benefits of understanding soil composition go well beyond texture and structure. It also has the potential to improve sustainability—specifically in the realm of water management. Knowing how soils retain moisture can help viticulturists more precisely determine the correct amount of water to deliver each vine.
“Irrigation in vineyards with clay soil is different from those with stony soil,” says winemaker Teresita Ovalle of Viña Santa Rita, one of the largest wineries in Chile. Clay soils, for instance, retain more water than those with a higher percentage of gravel. Therefore, vines in clay soils need to be irrigated for shorter periods compared to vines on rocky soils. This not only helps wineries save water, an increasingly precious natural resource, but can also reduce energy costs.
After working with geologists, Ovalle decided to separately vinify grapes from various geologically superior sites. Each area produced a high-quality wine with different characteristics—some muscular and tannic, others more elegant.
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“The tannins and structure of wine are determined by the place where the vines grow,” says Ovalle. “In our Alto Jahuel vineyards in Maipo Valley, we can compare a Cabernet Sauvignon that grows on colluvial soils in the hills with one that grows on alluvial soils. The latter has silky and rounder tannins than the wine that comes from the hill.”
Another geology convert is Andrea Ferreyra, winemaker at La Celia, which was founded in 1890 in Argentina’s Uco Valley. Though she has long believed in a holistic approach to viticulture and winemaking, geology has only recently become an integral component of her work.
“We used to think of Uco as a region with higher altitude, a cool climate, more rainfall compared to other regions and a large diurnal temperature range,” says Ferreyra. “But we didn’t stop to think about what lies beneath the ground—currently, we consider everything as a whole.”
To date, around 30% of the soil on La Celia’s estate vineyards has been analyzed. Those studies have already paid off: Last year was one of Argentina’s most challenging harvests, with grapes ripening unevenly due to frost. But fruit harvested from one of Ferreyra’s soil-analyzed vineyards proved her saving grace. Using knowledge from the study, she managed each plot separately as best suited them, monitoring the vines’ vigor and carefully calibrating the amount of water delivered. Even in a bad year, it yielded notably good fruit—albeit in lower quantities than had the frost not occurred. Still, in a sense, the soil analysis proved something of an insurance policy.
Looking to the Future
The work of geologists in South America has helped the continent’s wine industries to advance substantially over recent years—but their work is far from over. Both scientists and winemakers continue to strive for a deeper understanding of each subregion and appellation.
“Vineyards in places like Mendoza won’t [physically] expand much more due to the lack of water,” says Corona. In other words, in general, producers won’t be able to find new sites to plant vines. But if they’re able to better utilize the resources they do have on hand—the soil, for example—they may be able to increase the quality of their products and make more terroir-driven wines. “What we need to do now is to continue studying each region in detail to fully understand it,” he says.
Unlike those in Old World wine regions, producers in South America may not have centuries’ worth of knowledge about their vineyards. But geology is helping them gain a deeper understanding of their land and its possibilities. Already, high-quality bottlings have proved that knowledge is power.
“The more information and data we have, the better decisions we can make,” says González.
Published: February 14, 2024
