Vineyards, Rocks, & Soils: The Wine Lover’s Guide to Geology by Alex Maltman, Oxford University Press (2018)
The futility of writing a book review (or anything else for that matter) after British wine writer Andrew Jefford has already tackled the subject hit me hard the other day. His brilliant review of Alex Maltman’s Vineyards, Rocks, and Soils: The Wine Lover’s Guide to Geology convinced me to buy the book—which I devoured—but left me unable to express my own thoughts without parroting his. There was simply nothing for me to add. So, I began to think of another way to honor the book. Perhaps in a way that might actually contribute to the discussion. I came up with a simple idea: why not apply its science to the particular area that interests me most—Switzerland’s diverse vineyard geology. In this way the book’s teachings are brought to life and a topic that is little discussed is advanced.
First some background. Professor Maltman’s stated purpose—to introduce basic geology in the context of wine—is worthy in itself, but he goes beyond that to correct some common misconceptions and tropes about the effects of rocks and minerals on the wines we drink. As Mr. Jefford states in his eloquent forward:
“Alex Maltman’s book is an essential call to order. With patient clarity, he explains the geological fundamentals that every wine lover should know . . . He offers the wine world a terminological reset. The chance to start anew, our language cleansed and calibrated, makes this book essential reading for anyone who wishes to teach or write about wine or even think clearly about wine.”
Everything the wine lover should know, but often gets wrong, is the underlying message.
The book explains the impact geology has on viticulture while dispelling myths about what it contributes to the glass. Thankfully, Maltman excuses those of us who use geological metaphors to describe a wine’s characteristics, but reminds us that such descriptors are correctly used only as metaphors.
If we start with one of the book’s broadest points—that three-quarters of the earth’s surface is of sedimentary origin—then it’s fair to assume that vineyard land may represent an even greater percentage than that. After all, The matrix of limestone and clay is the Holy Grail of vineyard geology and some combination of the two is thought to be ideal. But, as Maltman asserts, limestone plays only a small part in the world’s vineyards; it’s presence is dwarfed by the siliceous mineral known as clay. Clay makes the chemistry happen, facilitates water and nutrient uptake, and even in its various forms is reasonably soft and workable. And it’s ubiquitous.
Next up, the one geological formation that is, perhaps, best suited to the vine: the hillslope. There are, of course, many other possible formations that are vineyard friendly but Maltman zeroes in on this one. Burgundy’s Côte d’Or is the most obvious example of the hillslope but the Mosel, Duoro and Alto Monferrato can be cited as well. In geological terms, a hillslope is the coupling element between mountain summits and a draining river system. The importance of hillslopes to viticulture is explained in Chapter 8 (The Lay of the Land):
“Vineyards on hillslopes catch more of the sun, avoid frost pockets, and are likely to be well drained—all special advantages in moister climates.”
So the sloped vineyard set upon an argillaceous limestone base is pretty close to ideal. Coincidentally, Switzerland has a few of those.
The Plateau Vineyards
The central plateau offers a complex mixture of geological features including glacial moraines and molasse featuring alternating beds of sandstone and marls. Conglomerate rock is the central feature of the Lavaux landscape which was created by alluvial fans which extend into St. Gallen. Moraine covers the molasse in many places, particularly in the regions of La Côte, Lake Neuchâtel, Lake Zürich and the Thur valley. geologieportal.ch
Lavaux—The Lavaux hillside of canton Vaud sits above Lake Geneva at a frightening angle and provides one of the most dramatic landscapes in the world. It’s famous terraced vineyards are barely held together by a network of dry-stone walls that increasingly require the assistance of geological engineers to reinforce. Lavaux also represents a fascinating bit of geology. This scenic hillside is one of a series of alluvial fans that shape the Swiss pre-Alps along their entire length to St. Gallen. It is also one of the few conglomerate formations in Switzerland planted to vines. The area was originally formed with sediments from the Bernese Alps—mostly from rounded pieces of sedimentary rock—which were then cemented by silica into a concrete-like rock. It’s common name is puddingstone, or poudingue, as it’s known in the French-speaking cantons. On the lesser inclines to the west of the formation, towards Lausanne, the soils are deeper with clay, sand and gravel. On the steeper inclines to the east, as at Dézaley, the soils are much thinner with exposed poudingue a common feature.
As testimony to the inherent instability of such formations, Maltman describes the catastrophic rockslide in Abymes, France in 1248 (Chapter 8: The Lay of the Land). He could have cited a similar 12th century event in the village of Epesses in Vaud where a rockslide that killed many villagers resulted in the formation of the Grand Cru terroir of Calamin. Today, that deposit rests atop poudingue and, unlike its rival Dézaley, its soils are deep and well-drained. It is thought the difference between the wines of Calamin (lean) and Dézaley (rich) are attributable to the unconsolidated debris of that ancient landslide.
In an interesting twist, the Chamber of Commerce-inspired “Three Suns” of Lavaux has a geological basis. In Chapter 10: Soil, Water, Sunshine, and the Concept of Terroir the author pays considerable attention to the concept of albedo. Albedo is a measure of the amount of light that strikes a surface and, without being absorbed by the ground, is reflected back. Higher reflection values equate to greater vine activity and ultimately greater ripeness. The “Three Suns” is not just a slogan but another way to acknowledge the principle of albedo; direct light from the sun (one) is enhanced by reflected light from Lake Geneva (two). The third “sun” is the amount of heat energy absorbed by dry-stone walls during the day and reradiated in the evening. Lavaux and its position among the northerly vineyards of Europe is one of the best examples of the influence of albedo. Maltman points out that “the influence” of reradiated heat “is more significant in cooler regions and at night.” That describes Lavaux to a T, where the diurnal temperature range is among the greatest anywhere.
La Côte and Geneva—La Côte, Geneva and Lavaux share a ninety kilometer stretch of Lake Geneva’s north shore, but from a geological standpoint they couldn’t be more different. In fact, if it wasn’t for the moraines created by repeated glacial episodes, the Lake Geneva basin west of Lausanne would be as flat as the proverbial pancake. Quite unlike the looming conglomerate rock face of Lavaux. The one unifying factor is the bedrock of the Central Molasse Plateau which is buried beneath tens of meters of glacial till.
Maltman describes the formation of a moraine as the “disorganized dumping of sediment from melting ice.” As in the melting ice of the retreating Rhône Glacier. Rock fragments of many shapes and sizes, including boulders, were transported long distances before being deposited as glacial till. From above, the vineyards of La Côte and Geneva resemble a series of raised parentheses, or the work of a giant bulldozer, that sit between the north shore of Lake Geneva and the Jura Mountains.
The vineyards of La Cœur de la Côte (the heart of the slope) are the steepest, highest and, not coincidentally, the best. As one would expect from the sequence of erosion most of the larger chunks of limestone and sandstone are found near the top of the slope while gravel, sand, clay and silt are found near the bottom. Reflected light from the lake is also most pronounced here.
After glacial deposition, alluvial flows have contributed to the shaping of the slope. Underground creeks on their way to the lake frequently appear at the surface bringing with them sediments from higher elevations. Over time the lake has also receded leaving behind a kind of bench with gravel and sand deposits. There are successful vineyards in the shoreline villages of St. Prex and Buchillon where the Bordeaux varieties Merlot and Cabernet Franc do well.
Geneva’s best terroirs are actually located a considerable distance from the lake and do not benefit from its reflected light. Instead, they are found on moderately sloping moraines, many with uninterrupted vineyards. The Mandement (Rive Droite) commune of Satigny is the largest wine commune in Switzerland with 450 hectares. Its soils include the same glacial till as at La Côte, but with more sand and gravel and a sticky clay that anyone who likes to trek in winter knows well
The area known as Entre l’Arve et Rhône (between the two rivers) is also based on glacial till but with a lot of limestone sediment (pebbles) brought from Mont Blanc which is the source of the Arve River.
The area known as Entre Arve et Lac (Rive Gauche) is the most spread out of the Geneva wine-growing areas and is the least interesting. It is based on glacial till but its soils are particularly heavy with sticky clay and are orientated to the sun at indifferent angles.
The Alpine Vineyards
In the Alpine valleys, vineyards are located mostly on alluvial cones, debris slopes and rockslide masses. Debris from Alpine limestones dominates in the northern mountain chains. In the central valley zones, particularly in canton Valais and the Alpine Rhine valley, there are flysch sequences and Bündner schist. Sandy calcareous soils originate from these interbedded sandstones, marls and calc-schists. geologieportal.ch
Bündner-Herrschaft—The Bündner-Herrschaft of eastern Switzerland is recognized as an important source for some of Europe’s best Pinot Noirs. It’s an idyllic landscape dotted with picturesque villages and neatly kept vineyards. The predominant rock of the region (northern Alps) is the so-called Bündner schist, a Jurassic-edition metamorphic rock of sedimentary origin. It’s alternating layers include limestones and sandstones with chlorite and dolomite deposits. It is the weathering of Bündner schist that creates the characteristic scree cones for which mountain-capped hillslopes, like Bündner-Herrschaft, are known. The unconsolidated scree, or colluvium, is the most recent geological layer and when mixed with humus, the organic matter in soil, the vine has all the nutrition it needs and the capacity to either store or drain away excess water as needed. The occasional giant boulder in the middle of a vineyard is persuasive evidence that gravity is at work here.
The downside of the hillslope (no pun intended) is its propensity to erode. Scree sits loosely atop bedrock and is subject to slippage. On the steeper slopes, or upper halden, larger rock fragments tend to provide greater friction and, thus, greater resistance to sliding. The finer sediments, like sand and clay, are further sorted on their journey downhill before settling near the bottom. That’s why the deepest soils are always at the bottom of a vineyard and the poorer, thinner soils near the top. Anecdotal evidence provided by Georg Fromm suggests that erosion forced early farmers in the Bündner-Herrschaft to painstakingly retrieve soil by hand from near the Rhine River to replace that which eroded. This, he explains, is the reason why there is so much sand in the lower vineyards of Malans.
The village of Fläsch sits on a different underlying rock—the soft and crumbly mineral known as diatomite, or kieselguhr in German. Diatomite results from the lithification and fossilization of siliceous deposits from oceanic organisms. Some of the locals actually confuse it with chalk. Diatomite has the handy capacity to both drain and retain water which is a neat trick in times of imbalance. It is extremely friable and offers little resistance to vine roots. Its presence in a vineyard is thought to add finesse, acidity and purity to wines that come from it.
Valais—The upper Rhône valley of Valais is a steep-sided, U-shaped valley located between two alpine ridges. Even though a great river flows through it, the valley was shaped by the repeated advance and retreat of the Rhône Glacier. Colluvial debris (as discussed above), rockslides, and alluvial fans shape the hillsides along the south-facing right bank of the Rhône while moraines near Sion and Sierre add alternative rock formations and visual drama to the mix. The most common rocks in the valley are interbedded calcareous schists, sandstones and marls, with gneiss and its derivative migmatite.
The author first mentions Switzerland when he describes a hillside vineyard in Valais with gneiss as its bedrock (page 103). He is referring to the vineyards of Fully. This tiny wine village touts its position atop some of the oldest rock in the Alps and even makes the unsubstantiated claim that it is the ancestral home of Petite Arvine. Gneiss and Arvine are an odd couple because weathered gneiss is a very poor reservoir for water and Arvine likes to drink, a lot. Such a partnership requires irrigation which is supplied by melting snow from the upper Alps transported by man-made open ditches known as bisses.
The weathered gneiss of Fully does offer one advantage to the viticulturist: its significant mica component provides relatively high albedo values because of its almost unequaled capacity to reflect sunlight. The rows between the vines can, in fact, be blinding white on a sunny day.
Gamay, another Fully favorite, also mixes well with gneiss and is the predominant red of the village.
Further afield, as we travel west, interbedded calcareous schists are a feature of the middle valley beginning at Leytron and continuing through Chamoson, Vètroz and parts of Sion. Maltman refers to the wine consortium known as L’Association Terroirs des Schistes which highlights wines grown on schist. Several members are located in this part of Valais, including Jean-René Germanier and Cave du Vieux-Moulin. They, like others in the group, claim that schist wines are more aromatic with more freshness, acidity, minerality and salinity than the same grapes grown elsewhere. Maltman is appropriately skeptical when he points out that different schists are unlikely to manifest different qualities. A schist, is a schist, is a schist, is his point.
Very hard, brown sandstones appear on the Lentine Hill in Sion before flysch formations emerge in the upper valley at Sierre, the Coteaux de Sierre, Les Bernunes, and Salgesch. Flysch is defined as a sedimentary sequence of interbedded sandstones, conglomerates, marls, calcareous shales, and clays formed during mountain building. It is in this area that Pinot Noir begins to take over as the dominant red variety, although the natives, Rouge du Pays (Cornalin), Humagne Rouge, and near native, Syrah, are gaining ground.
The vineyards above St.-Léonard are somewhat unique in the valley as they sit upon dolomite (a magnesium-rich limestone) and a rare pocket of gypsum, as evidenced by the working quarry below the vineyards.
Wind, although not a geological feature, has geological consequences. Strong, dry winds are a common feature of the Valais climate and their capacity to weather rock over time should not be underestimated. Wind is also an important factor in erosion and the reason why loess, which can be born great distances by the wind, is a typical component of vineyard soil. Weathered flysch is often sandy and grainy but when mixed with loess its water retention capacity is much improved.
One geological feature in Valais that doesn’t have anything to do with viticulture, but is interesting nonetheless, is the inselberg. Anyone who has been to the small city of Sion will have noticed the old medieval church set upon a stark hilltop. It’s a remarkable sight because the valley floor is otherwise perfectly flat. Even the Rhône River makes an abrupt left turn at its base before continuing its downhill course through the valley. Geological maps reveal the reason why: The Valère hill is composed of the only quartzite rock in the area and as Maltman explains, quartzite is close to indestructible. It may also suggest why the hill next to it—capped by the Château Tourbillon and made of less resistant sandstone—survived as well. Quartz-laden sandstone is a precursor of quartzite rock.
Gneisses and mica schists form the base of the vineyards in the Alpine valleys of canton Ticino. Weathered layers and moraine covering, of varying thickness, commonly lie on top of this bedrock. In the far south, the vineyards of Mendrisio thrive on volcanic rocks, Kieselkalk lime- and marlstones, conglomerates and moraines. geologieportal.ch
Ticino—Ticino sits at an odd place in Switzerland—south of the alpine ridge and, in some places, near its lowest elevations. Yet the bedrock and geological formations are distinctly alpine. For wine purposes, the canton is usually divided into two parts: north of Monte Ceneri (sopraceneri) and south of Monte Ceneri (sottoceneri). I would propose a third part: south of Monte San Giorgio. It is there, around the city of Mendrisio, where orthogneiss (gneiss of igneous origin), as well as granite and rhyolite are found.
The Sopraceneri is characterized by granite and the wines from it, mostly Merlot and the local specialty Bonarda, are more rustic than fine. It’s my feeling that the rusticity is due to winemaking choices, vineyard composition and higher elevations than due to bedrock.
The Sottoceneri has a more diverse profile of paragneiss (gneiss of sedimentary origin), dolomite, limestone and heavy clays. The combination of limestone and clay is particularly synergistic, as we have seen, and the deep clays of Ticino are often compared to those of Pomerol in France. It’s no accident that Merlot is king in both locations.
High annual rainfall (the highest in Switzerland) and high humidity are often cited as an obstacle to organic viticulture in Ticino, so fast-draining soils and drying winds are essential.
The Jura Vineyards
In the Jura Mountains between Neuchâtel and Schaffhausen, the vineyards are widespread on marls and on slope debris of Jurassic limestone, which are very rich in nutrients thanks to a high clay content. geologieportal.ch
Neuchâtel, Lac de Bienne, Basel-Landschaft, Aargau and Schaffhausen—The vineyards of Basel-Landschaft, Aargau and Schaffhausen share some common characteristics. They are all influenced by the Jura Mountain chain and its unfolded section to the northeast known as the Table Jura. This particular section shares the same sedimentary origin as the folded Jura but was never disturbed. The crucial rock types are oolitic limestone, calcareous sandstone and marlstone, set beneath both glacial moraines and alluvial fans.
Basel-Landschaft and Aargau, west of the Aare River, share calcareous sandstone, limestone and chalk-like oolitic limestone. East of the Aare River, near Klingnau and Döttingen, marlstone is more common with some deposits of blue-clay, a highly revered type like that of Château Petrus in Pomerol. All of these rocks pop up in different places, but for the most part they are a recurring theme—from Maisprach in Basel-Landschaft to Klettgau in Schaffhausen.
One point of difference with the Klettgau is the appearance of muschelkalk, a particular form of limestone sediment that exists in the presence of both magnesium (dolomite) and gypsum. The Gächlingen hill and some of the Hallau vineyards contain deposits of muschelkalk.
Neuchâtel and Lac de Bienne (Bielersee) are located southwest of the Table Jura and are significant hillslopes composed of limestone debris. Both areas hover above their respective lakes which, as we have seen, can offer significant ripening assistance.
In the village of Auvernier, the heart of AOC Neuchâtel, white and yellow limestone can be found, while to the northeast, in Hautrive, reddish limestones are present. From my own observation the Pinot Noirs from Hautrive are more structured with less finesse than the delicate, aromatic examples from Auvernier. Professor Maltman might point out there could be several other reasons for the difference and none of them geological.
If you love wine, no, if you LOVE wine, then you must get this book. I see it as a never-ending resource for some of the really geeky aspects of wine as it relates to place. It’s not dumbed-down but it’s easy to grasp. My own research for this piece led me further afield than just the contents of this book, but that’s a great thing. It steers you in the right direction and gently tweaks you when you begin to move off-course. I feel smarter for having read it and, in a way, humbled by what is still out there that I don’t know.
Kind of like wine.