Alto Piemonte’s supervolcano and why it’s important.
“L’evocazione non si perde, si dimentica.” - Christophe Kunzli
Alto Piemonte’s viticultural past has been forgotten about for almost three generations. But as one of Italy’s most historic wine regions, shouldn’t we be asking ourselves, “what is its story?” To get to the bottom of this, we must first understand what makes this terroir so unique.
a geological UNESCO world heritage site
“It’s something magical you can feel as you walk through the vineyards” - Luca de Marchi of Proprietà Sperino.
In 2013, the Sesia Val Grande Global Geopark was declared a UNESCO world heritage site because of its extremely unique soil makeup that exists nowhere else in the world.
It all started with a supervolcano...
Six hundred million years ago, all of Earth’s landmass was composed of one supercontinent called Pangaea. Between 280 and 290 million years ago, a giant volcano formed on this massive continent. Then, a catastrophic event took place roughly 100 million years later - the volcano exploded and collapsed in on itself, “forming a caldera at least 15 kilometers in diameter.”
The other important event surrounding this supervolcano took place 50 million years ago when the African plate collided with Europe, forming the Alps. As Africa opposed the supervolcano in the Sesia Valley, its force caused the crater to overturn, exposing the inside of the volcano to the earth’s surface in a horizontal manner.
This unique series of events means that Alto Piemonte is the only place in the world where the topsoil is made up of the same material that surrounds the Earth’s core in the rest of the world. As you walk through the vineyards of Boca or Gattinara, you are actually walking upon the mantle of a prehistoric volcano - the part of the earth that in the rest of the world is 30 kilometers underground! In other words, the deepest layers of the Earth are located at the surface. This differs greatly from the other supervolcanoes that we know of today that lie completely underground (Yosemite in California and Campi Flegrei in Campania, for example). As such, Alto Piemonte is the only place in the world where it is possible to examine the inside of a volcano.
Surprisingly given the size of the volcano, this discovery is a very recent one. Geologist Silvano Sinigoi, who is a Professor of Petrography at the University of Trieste and James Quick, a Geologist and Dean of Dallas Southern Methodist University (Silvano Sinigoi), made the hypothesis in 2011 and later concluded it in 2015.
Why is it important and how does it impact the wines?
I. Reason Number One: Acidic Soils
After the supervolcano exploded, its crater remained open, exposing it to rain and other elements during this time. This led to the gradual erosion of the crater’s interior, contributing to the soil's acidic nature.
At roughly 400 to 500 million years old, the soils of Alto Piemonte are arguably Italy’s oldest. To put this into perspective, most of Italy’s soils are 5 million years old: the marls of the Langhe are 3.5 million years old and the Roero’s sandy soils are 2.5-3 million years old.
Moreover, because of their extremely old age, these soils have absolutely no limestone which make them some of the most acidic soils in the world (certainly the most acidic soils of any major wine region). Typically, when talking about vineyards, the opposite is true - most vineyards contain at least some active limestone, and its presence is often regarded as a positive attribute. Some of the most renowned wine regions of the world are famous for their high percentage of active limestone, with the most classic examples being Chablis, Champagne and Burgundy.
(Because Alto Piemonte’s soils are so old, they are friable in nature, so roots can dig deep in search of nutrients. But let’s stay on track here…)
What impact do acidic soils have on the plant and ultimately on the resulting wine?
In acidic soils, all metals in the ground are available to the plant. To better understand this, let’s compare acidic soils to alkaline soils. Soils that are alkaline, meaning they have a high presence of active limestone, are not able to access metals such as aluminum, phosphorus and potassium in the soils because the limestone (calcium carbonate) blocks them, preventing the vine from accessing them. (This is especially true in marl and clay soils.) In acidic soils, there is no limestone to block these metals, so all of them are available to the vine. “For better or for worse” explains Luca de Marchi.
For Worse: These metals are sometimes too available to the vine - they can actually be poisonous to the plant. In the summertime, you’ll notice that the leaves here don’t take on the beautiful shimmery green color that they do in the Langhe. Instead, the leaves appear eroded, with broken yellow and black-speckled leaves. This is evidence of metal corroding the plant.
This means extremely low yields. Magnesium dries out the flowers, resulting in very sparse clusters and low yields. Today we typically associate low yields with higher quality wines. While this can be true in many cases, it is one of the major reasons why so many producers left their vineyards in the early 1900s to go work in the factories, leaving vast tracts of viticultural land in complete abandonment. (The region has only begun to recuperate a miniscule fraction of these vineyards that once enveloped the entire region.) Quantities are so low that mass-production in the 20th century was not an option, and at the time, people were not prepared to pay for quality. It simply did not make economical sense to produce wine.
In the Langhe, if you thin your crops (green harvest being the most obvious example), Nebbiolo will still produce 10 tons per hectare on average. In Alto Piemonte, without any crop thinning, the vineyard will struggle to produce 6 tons per hectare.
For Better: Since the vine has access to these minerals in acidic soils, the wine itself gives off the perception of minerality. High amounts of potassium create a noticeable saline component in the wine. Sometimes it is so apparent that it can be off-putting if not properly balanced. Bramaterra, which has some of the most acidic soils in Alto Piemonte, can sometimes come across as extremely earthy and sanguine, with aromas or iron and rust due to the enormous quantities of potassium in the actual wine.
***It is important to note that this phenomenon holds true for all the denominations of Alto Piemonte except for Lessona. Lessona varies from the other denominations of Northern Piedmont due to its prehistoric marine sands (see the regional guide on Lessona), which differ from the much younger sandy soils of Roero.
Lessona’s soils are a direct result of the Valsesia super volcano, but are different from the soils discussed above because of how they were formed. As Africa collided with Pangea and the supervolcano was turned on its side, it scratched the bottom of the sea bringing with it sand from the seabed. Because Lessona sits at 280 meters above sea level, when the Mediterranean covered Pangea and then receded, it did not take the sands with it.
II. Reason Number Two: the Alps create a unique microclimate that prolongs the growing season
“Mild winters, cool summers, and a very long growing season - the complete opposite of what you’d expect from an alpine region.” - Luca de Marchi
Another consequence of the supervolcano is made evident by the palm trees, banana trees and other tropical plants growing throughout Alto Piemonte. This might seem strange in such a northerly location at the foot of the Alps, but it is actually the mountains themselves that create this unique micro-climate.
In the Western Alps (or the Pennine Alps), the mountains are extremely vertical and form a protective wall that towers over the vineyards below. Unlike the rest of the Alps, the mountains here were not formed by Africa slowly running into Pangea (modern-day Europe) over time. Instead, the Alps in Alto Piemonte were created with a much quicker and forceful action - the mountains shot out of the ground as the supervolcano turned on its side as described above.
The eastern side of Monte Rosa, which faces Alto Piemonte, is considered a “Himalayan wall” because of its verticality. La Punta Dufour (Dufourspitze in english), Monte Rosa’s highest peak, has one of the highest cumulative elevation gains in the world. Within a span of just 10 kilometers, it rises from 100 meters at its base all the way up to 400 meters (fact check).
Vertical Gain: 2054 m/6739 ft (https://www.peakbagger.com/peak.aspx?pid=10043)
Further modering Alto Piemonte’s winters are the warming Fohn winds from Switzerland that can raise temperatures to 20*C in the heart of winter!
This results in a climate that differs greatly from Valtellina, Valle d’Aosta and other “mountain wine regions” with which Alto Piemonte is often associated. “We don’t produce mountain wines here. In fact, it is quite the opposite,” explains Luca de Marchi. The vineyards of Alto Piemonte sit below the mountains, not in them.
Thanks to the verticality of the Pennine Alps, cold northerly winds in the wintertime hit these mountains, skipping over the vineyards of Alto Piemonte, and falling onto the area of Monferrato farther south. As a result, winters in Alto Piemonte are extremely mild - it is very uncommon for it to snow here (temperatures rarely dip below 5 or 6 degrees Celsius) and winter is the sunniest season. Whereas three meters of snow is quite common in the Langhe, Alto Piemonte receives on average just two centimeters (less than an inch)!
Rainfall on the other hand is quite high (41 inches on average per year), with most of it falling between April and May, so fungal diseases can be a major concern.
While the Alps keep Alto Piemonte warm in the winter, they also keep the region cool in the summer. Because of Monte Rosa’s many glaciers, cool breezes travel down from the mountains into the vineyards, while warm air from the plain rises up to fill this void, meaning that temperatures rarely rise above 30*C (86*F) in the summer. This cooling factor further prolongs the growing season and harvest typically takes place in mid-October.
While the cooling influence of these glaciers help contribute to the elegance and beauty of these wines, they also create Alto Piemonte’s largest viticultural threat - hail. As cool air from the glaciers interacts with the warm air from the plain, hail can form. This usually occurs in the fall, right around harvest when berries are at full maturity, so one hail can completely destroy an entire year’s crop.
Alto Piemonte’s growing season is typically 2-3 weeks longer than it is in the Langhe. This difference is evident in the resulting wines, which exhibit grace and elegance. Cooler summer temperatures mean that the wines have a lighter color and gentler tannins than wines from the Langhe, where warmer summertime temperatures encourage the development of polyphenols (resulting in a darker color) but can also burn the aromatics.
In “mountain wine regions” such as Valle d’Aosta and Valtellina, the growing cycle is generally much shorter because of the early onset of winter and the delayed budbreak due to cold temperatures into late spring months. This is the reason why, historically, the wines of Valtellina underwent appassimento, a process in which berries are left to dry before vinification. The goal of this process was to encourage green tannins in the skins and seeds to mature in a climate where fruit typically does not have adequate time to fully ripen in such a short growing season.
Compared to the Langhe, Alto Piemonte’s growing season starts 10 days earlier on average.
The unique microclimate of Alto Piemonte helps produce wines that are light in color and body, less tannic and more aromatic than wines from both the Langhe and “mountain wine regions”. Because of these differences, Luca de Marchi chooses a different style of winemaking than what may be common for Nebbiolo in the Langhe - “vinification in the Langhe tends to extract, whereas our methods here do not. In Barolo they can extract more because they have more ripeness of the seeds, tannins and skins. Our way of making wine is more of an infusion, in the sense that the wine stays on the skins and slowly and gently develops aromatics without too much extraction.”
I hope that if nothing else, this article has inspired a curiosity to learn more about a region that Italians would describe as unico. The phenomena of the supervolcano, the way we can observe it and the influence it has on the wines is fascinating but is very much uncommon knowledge. My hope is that this information will be disseminated to sommeliers across the globe, because it is truly a story worth being told.