Article: Soil under Loupe

No. 2

We can be baffled about the long history viticulture has. Thousands of years seems intangible, but those thousands of years of wisdom, culture and experience we consume when we drink a bottle of wine. And not only that: The drops are forged by rocks created millions of years ago in a time were dinosaurs ruled and tectonic activity created Pangea only to rip it apart.

Rocks were compressed, heated, molten, shaped, transported and surfaced to weather down over the span of several ages.

Rocks are cornerstones in our understanding of terroir and still we are only starting to unravel their impact on wines.

In this issue the focus is on the origin and signature of the most important vineyard rocks.

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2022

Soil Under Loupe B Y: N I N A H Ø J G A A R D J E N S E N

In making a bottle of wine there are literally thousands of variables – most of them invisible to the human eye. One of the most intangible subjects must be soil. Not so much from the geological perspective but most certainly when it comes to the direct effect it has on a wine. In wine terms we usually barely scratch the surface of the geological meaning of a soil yet, we talk about it constantly assuming a position of knowledge or deeper understanding. Expanding further on an article started in issue no.3 2021, we here take a deeper dive into the formation of key soil types and spikes it with the wisdom of certain experts.

The build of this article is perhaps somewhat different to what we commonly see in our magazine. If you prefer to only read about selected soil types, each paragraph can without further ado be read and understood singularly.

To make sense of the distribution of soils across the globe we will need to take a look at certain periods of time to understand from where the soil types are derived and how they are distributed globally.

What is a Mineral?

Apart from a frequently used word in the world of wine, a mineral has a set of chemical definitions it must uphold to classify as such:

are linked. Minerals has its atoms linked in a beautifully ordered, crystalline fashion meaning the same number of atoms can exist in different forms – sometimes in a mineral and a non-mineral form. Ice as an example is a mineral while liquid water is not despite them having the same chemical form of H2O.

- Naturally occurring - Solid - Has a crystal structure – decides the formation in which the atoms within a molecule

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A F: N I E L S F I N K, V E J R H Ø J V I N G Å R D

- Has a defined chemical composition - Is inorganic - not formed from life Only on very seldom occasions does minerals from the soil exist in the actual finished wine yet, it is a widely accepted tasting notes with nuances bound to it. The metaphor as a tasting note is not entirely spun from thin air: It makes sense from the perspective, that minerality can describe a texture or a lack

of fruit which we associate with the physical composition of what is defined chemically as a mineral. Thus, there is an analogy between what a mineral is and how we use it as a metaphor. In soils minerals are a decisive factor of soil texture, pH values and nutrient availability. Rocks are composed of minerals.

Soil is composed of organic matter, minerals, wind, water and air.

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TA S T I N G T H E OMNIPRESENT Clay is a necessary starting point. Pedro Parra attributes it with being “The most viral part of wine typicity”. Firstly, because it exists in every single vineyard across the globe (except on Santorini – more on that later). Yes – every vineyard. Even the smallest amounts make a difference.

Secondly because our language surrounding clay is not very precise; unfortunate as some of the most famous terroirs are clay dominated.

Now clay - what is it referring to? The simple definition would be a particle size. Clay has the tiniest particle size of any soil type, invisible to the naked eye with a maximal diameter of 0,002mm and often way smaller than that.

Due to its microscopic size, it is difficult to both study and to understand. Its invisible nature has made geologists taste soil to see if it is clay or silt: Clay will be silky in the mouth while silt appears the same to the eye but will have a grainy texture in the mouth.

Perhaps the rumor of geologists licking rocks originates from this? Clay is formed by rocks breaking down and is the inevitable end destination of many soils.

ed into a flat, sheetlike, layered structure with aluminum and water built into their structure. They form when rocks weather down into clay sized particles and these partake in chemical reactions forming new, tiny minerals.

Clay minerals can also be referred to as “true” clays and has completely different attributes compared to clay defined by particle size alone.

They make things happen! A key feature of a clay minerals it their gigantic surface area: Surface area of various grains: - 1g of spherical sand = 11 cm2 - 1g of spherical silt = 1130 cm2 - 1g of spherical “non true” clay = 113.000 cm2 - 1g of spherical clay mineral = 11.300.000 cm2 (1130 m2) minimum, often more

“T R U E” C L AY S

The true clays vary in accordance with their parent material (which rock has weathered to become true clay) and the weathering process itself.

Variables includes grain size, color, swelling, water holding capacity and cation exchange ability. Soils often contain several types of clay.

Clay is not only a particle size.

The term clay also covers clay minerals that are formed from weathered minerals compact-

Clay is chemically active and plays a key role in nutrient availability and uptake. As

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most chemical reactions occur on the surface of solid grains the huge surface of clay makes it a highly active soil type.

Clay minerals are negatively charged while soil nutrients (=cations) are positively charged. Cations are held in soils by clinging to the clay minerals via their opposition in charge. Through the roots the vine (and other plants) can decide to exchange their own cation, which is hydrogen (H +), with the cation existing in the soil it needs. This process it referred to as the cation exchange. A soils cation exchange capacity is measured by its ability to withhold nutrients and make them available to the plant through this process. However, the surface area is not always linearly linked to the CEC (Cation Exchange Capacity).

To Pedro Parra montmorillonite clay (smecite family, swells when wetted and has small particles) is the holy grail of clays: “The complex alluvial soils have very high-quality clay, called montmorillonite clay, and some have a limestone component.

It’s calcium carbonate technically, but in the mouth, it feels the same as wine grown on limestone. Clay is like chocolate — you can get chocolate for a dollar at the local petrol station, or chocolate for $100 dollars from a top Parisian chocolatier!”.

On the opposite end of the spectrum we find kaolinite which doesn’t swell and has large particles in comparison to smectite – Pedro has nothing nice to say about this type of clay, “I won’t say much about it other than it is bad.

This is one dollar chocolate You don’t want that in your vineyard”.

When we think of clay, we rightfully associate it with heavy, sticky soils. Working in a clay vineyard can be hard and troublesome to work – especially after rain. It will contribute to a compact structure in the soil and provide great water retention, sometimes even too great. It all depends on what exact clay

you have and in what combination. Prue Henscke argues an important point: “What is missing from the soil triangle is – what is below here? If it is the hard bedrock, it will be poorer and create a restrictive growth while if it is clay it will provide plenty nutrients and encourage growth.”

And it is incredibly complex as just 1% difference in clay content can make a big difference in areas such as Margaux AOP where about 10% of the soil is clay. “Sand with clay is not the same as silt with clay. Everything is about nuance and detail” Pedro Parra says. It is also one of the special complications of working with clay: Our eyes can’t necessarily detect the difference

and that makes it complicated to understand. You can’t copy a vineyard practice from one place to another due to the details within the clay.

Clay in a vineyard will tend to raise the fertility. With that comes a longer growing season as the vine will bud earlier and result in a fuller body of the final wine. This correlates with several producers independently of each other talking about a certain clay texture in the wine as a sort of broadness.

Famed clay terroirs (variable in %):

Ribera del Duero

Bordeaux: Potential of gravel depends on the underlying clay. All the clay in Bordeaux originates from Massif Central, but Petrus as a deeper layer.

Oak Knoll District of Napa Valley Hill of Grace Barossa & Eden valley

Loire: many cases show Sauvignon Blanc actually prefers clay rather than flint: Coteaux Gienneois, Marlborough, entire Enter-deux-Mers, Pouilly-Fumé as examples.

Côtes d’Or especially: Chambolle-Musginy, Vosne-Romanée and Pommard. Top to bottom variation of clay on the slope in Côte d’Or: Towards the bottom there’s an accumulation of clay while on the top only very little clay can be found. Grand Crus in the middle has a balance.

Jura Barolo Montalcino Rioja

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Clay Definitions (1) Clay is an extremely fine-grained particle size, specifically anything less than 1/256 mm, or less than 2 micrometers (μm). This is invisible to our naked eye, and is also invisible to most microscopes

Common clay minerals include:

(2) Clay is also a type of mineral group (clay-mineral). These minerals are very small (clay-sized), hydrous aluminum silicates with a flat, layered structure. Clay minerals often form from the chemical weathering (breakdown) of other minerals.

- Illite: Smaller than Kaolinite but doesn’t swell.

- Kaolinite : Larger grains. Doesn’t swell.

- Smectite: Smaller grains. Swell when wettet.

- The French word for clay is argile Different types of clays originate from different rock types or from dfferent weathering conditions.

L I M E S TO N E, C H A L K & M A R L Limestone is very likely the soil type with the most positive associations. Over and over, we hear the mention of it almost as a self-explanatory reasoning to a wine’s greatness, and studies show we perceive it as pretty, perhaps partly due to its relationship to marble.

It belongs to the family of sedimentary rock and holds three subcategories: Clastic: Deposits that gets solidified. A clast is a piece of larger rock that is rounded by depositing Biochemical: Most limestones. Formed from living organisms that build tissue and shells which remain after the death of the organism and become limestone Chemical: Chemicals are weathered or pressured out of a rock to form limestone.

Any limestone has a minimum of 50% (CaCO 3 (CaCO 3 is also the mineral calcite), otherwise it categorize as something else which is the case of for instance most marl. It will often contain fragments of ancient marine life of shells, and the different types of limestone reflects their given disposition.

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Cretaceous Period

LO O K I N G B AC K I N T I M E Most limestone and chalk are formed by coral reefs.

The limestones and chalks we often hear about dates to Jurassic- (Kimmeridge, Oxfordian, Barthonian, Bajocian, Portlandian. Much of Jura and Bourgogne soils) or Cretaceous period (also Portlandian). The Jurassic period stretches from 199,6–145,5 milllion years ago, while the

Cretaceous time is more recent from 145,5-65,5 million years ago, but also some stretching all the way back to the Triassic period 251-199,6 million years ago (such as Muschelkalk, Keuper, Bundtanstein). The two first mentioned were warmer times than today with higher water levels and overall, more tropical climates. Additionally, it correlates with period where

Jurassic Period

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Pangea was being ripping apart, revealing dips in the landscape for water to cover and create shallow seas. With that knowledge, we can look back in time to paint an image of the global distribution of limestone and chalk and understand why most European wine countries have limestone while it is a scarcity in wine growing regions outside of Europe.

The formation of a coral reef Looking at the maps, all the turquoise parts surrounding the land mass would be coral reefs. We can clearly see how almost the entire landmass that would become France and large parts of Europe was a coral reef during Jurassic times, and later in the Cretaceous period, large portions of northern Africa, Central Africa and Central North America was forming limestone. Meanwhile the entire Westcoast of America formed the mountains so significant to the landscape today. Much of the limestone created would end up places not suitable for winegrowing such as top of high mountains or too close to equator, but in France ½ of the surface ended up being limestone while it is 1/3 for both Italy and Spain. Perhaps looking at the great history of viticulture shared by these countries, it is no wonder that limestone has gained such a reputation. Yet not everywhere limestone is to be found in the right climate for vines does it reign supreme: In

Alsace for instance, the first Grand Cru, Schlossberg, is not limestone and neither is the perhaps present-day king of Grand Crus Rangen de Thann. At the same time, we must realize, that even areas greatly associated with pure limestone are perhaps not that pure: In Champagne you will find plenty of marl (entire Côtes de Barr for instance) and large portions of sandier soils, in Cognac Borderies is sand and in Jerez Arena and Barros are widely spread just to mention a few examples.

Organisms have very specific conditions and depths they live at, but those from coral reefs are particularly good at building on top of each other. As the water levels rose and sank over time, biochemical limestone was formed in complex layers with varying dispositions reflecting the life lived there at the time of its formation. In some limestones we can even find a large number of intact fossils to witness the origin making the power 29

of time evident. The location on the reef similarly influences the dispositions: The forereef sees a lot of wave action and consequently the organisms there tend to be larger and studier creating bigger sediments, while the back of the reef in an atoll or barrier reef would be more calm water and create finer sediments.

The Paris basin exemplifies how the older of these chalks and limestones are normally buried deeper as they only surface on the outer edge of the basin, while, as we move towards the center, the soil changes and become younger. On the outer borders we find Alsace and Germany in the east on the Triassic band, while on the Jurassic band that follows, Burgundy, Jura, parts of Rhône are located. At the cretaceous band Champagne is laying as well as large parts of Loire which also has a great portion on the Eocene era.

F R I E N D LY I N C L I M AT E C H A N G E Despite being different in age and disposition there are some general commonalities between limestone soils: They are all alkaline due to the active CaCO 3. They are porous which they become by the breakdown of CaCO3 which releases CO2 to either the atmosphere or builds it into new minerals. This process degenerates the CaCO3 rendering the soil shallow without formation of clay.

The porosity is great as a water storing capacity. A high amount of CaCO3 can pose a problem with chlorosis in plants.

Limestone tends to draw forward the perfume in wines. Wines from limestone soils tend to have low pH and high acidity level, and according to Olivier Humbrecht, a very high

content of malic acidity. But that is only true with adequate water levels. Pedro Parra elaborates on how he feels limestone is ideal in wetter climates but can be a challenge on super dry locations: “Limestone is a rock that needs humidity. If it doesn’t have humidity and you try to make red wines, you will have rustic and dry, kinda heavy tannins. It can be difficult if you have too much heat. I could see that when I started to work in Rioja” Olivier Humbrecht agrees with Parra: “Water regime and heat is important when dealing with limestone. But we must also take into consideration the diversity in limestones. Some might be better at it than others. Also the match between varietal and soil. I for instance don’t 31

always like Riesling much on limestone – it needs a terroir that warms up quickly and allows the roots to go deep.

Then I prefer much more the Pinot family or Gewürtz on limestone.” Oliver also elaborates on the porous qualities of the limestone allowing it to store water: “Limestone is a popular remedy in the battle against climate change. It is maybe the best soil for that partly because of its ability to combat hydraulic stress, which is essential when temperatures are raising but the waterfall remains the same.

Any soil which is not limestone is more difficult to cultivate today. I can see them demanding the yields lowered and the vineyard to be overall managed differently because of draught risk here in Alsace.”

W E KNOW LIME S TONE F RO M:

Tuscany: Chianti and Montalcino

Champagne: Purest in Côtes de Blancs Chablis: Right bank of the river where we find Portlandian limestone and marl. Marl is soft and erodes into the center of the valley leaving the Grand Cru sites with more more pure limestone.

Piemonte: The younger tertiary Piedmont basin is 15-20mio. years old. Here the soils is very high in pH and the limestone is not so pure, often bordering marl with up to 30% clay in it.

Many places sand plays a significant factor as well contributing up to 60% of the soil.

You will also find a great deal of marl in Barolo and Barbaresco.

Loire: in Saumur and Anjou Blanc soils Côtes de Beaune: is actually more marl than limestone, while Côtes de Nuits is more hardened chalk Southern Rhône: has hard and very pure limestone in Vacqueras and Gigondas Languedoc: Pic Saint Loup, Minervois, La Clape, SaintJean-Minervois, parts of Corbieres Bordeaux: Saint-Emilion – calcaire aesteris (star fish limestone) – the higher on the plateau the more

Cahors Greece: Crete, Naoussa, Nemea Franconia: central part – also the oldest history of dry whites in Germany Spain: Rioja, Jerez, Catalunya Portugal: Barriada Outside of Europe: Coonawarra, Wrattonbully, Limestone Coast, Tumba Rumba, Robertson (South Africa) North Canterbury, Canterbury as well as small plots in Central Otago and Hawke’s Bay. Uco Valley in Argentina is one of the only places in South America.

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Variatioins of limestone: Marl – the dirty limestone Marl is essentially impure limestone, or as some geologists say: Dirty limestone. It has 35-60% clay in the mix and goes towards mudstone as the clay content increase.

ton. It is extremely white and extremely low in clay and silica. It can have too much active CaCO 3

Chalk – the rare and pure Chalk the exact opposite of marl. It is a super pure form of limestone form in vey deep water and made from the skeleton of plank-

Tuffeau: A type of limestone from the cretaceous period. Feels more chalky and is older than Tufa. Can be very calcerous.

Tufa: Soft, freshwater derived, decarbonated (low in CaCO3)

Outcrop of the Paris Basin 33

Silt = 0,004mm-0,062m dominating in vineyards al. Hunter Valley is a rar Brunate Vineyard (Barol tent. A good blending pa

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mm – very rarely seen s as it is too nutritionre exception as well as lo) with 70% silt conartner for many soils as

S AN D STONE AND SAND

Sand is significant. We rarely put it in focus even if some iconic terroirs have sand as an important component such as is the case in 1/3 of Champanois vineyards. Is it boring?

Unsexy? Or are the characteristics of sand so subtle that other factors steal the limelight?

Sandstone and sand are essentially solidified deposits on the earth. As a corner in the soil triangle, sand has a particular grain size of between 1/16 mm - 2 mm and the French name for it is sable. The grainsize of sand makes them very temperature transmitting, heating up quickly as well as cooling down fast. Easily recognizable to the eye sand, is not only the beautiful, glistening kind we can find on beach shores but can also be less softly rounded grains of different origins. it can lighten heavy soils and broaden lean ones.

Sand = 0,062 mm - 2 mm Loess = balanced mix of silt, sand and clay (max 20% of the latter) Sand is, due to its grain size and loose structure, easily transported by wind and water. The sorting and rounding of the individual grain will depend on where the sand comes from and how well it is sorted by transportation. Sand shaped by water will be more uniform in size and rounded than sand from weathering down of rocks on land. Any 35

type of rock or soil can have a sandy component to it. Black sand ig. Is formed of weathered basalt.

Sandstone is a sedimentary, clastic (composed of solidified deposits) kind of rock consisting of solidified sand.

Its dispositional environments are shallow marine soils and sand dunes. Oftentimes we see sandstone interbedded of coarse and finer materials.

Each bedding can be massive and homogeneous or thin, varying layers. The crossbedding is formed by wind or water streams.

Sandstone is characterized by high porosity and high permeability allowing air and water to easily flow through and creating a high potential of it harboring other materials such as oil or water. Sandstone has a better water holding capacity than sand itself does and will often bring a slightly fuller character to a wine.

Sandy soils are weak in fertility, low in organic matter, fast draining and often very deep making it necessary for the roots to grow long to feed the vine. The fast-draining capacity can pose a threat to the purest of sand soils as water become increasingly scarce during growing seasons in hot climates. One’s mind might immediately flicker to the famed Château Rayas, likely holding the crown as the most cult wine from sand soils. How long will they be able to refrain from irrigation?

Loess soil is in the family of sandy soils as a windblown, transported soil type consisting of a balanced mix of clay, silt and sand with a less than 20% clay content. Made up from fine grained sediments surfaced by glaciers and transported by wind, loess is found distributed all over the world.

Loess exists often in a calcareous version, but can also be decarbonated. It is differing a lot to pure sand in being nutrient rich and water retentive; perhaps it can be considered more aligned with limestone in its abilities. Important Loess terroirs are Kremstal, Crozes-Hermitage, Kaiserstuhl, Ningxia and eastern end of Tokaj including Hetzölö vineyard.

Contrary working in heavy clay or granite, working in sand is light and less costly as it doesn’t wear down machinery as fast. Baptiste Grangeon describes the wines of sand in Chateauneuf as less opulent than those from galettes roules.

The roots need to search deep for nutrition which impacts the choice of rootstock. Baptiste seconds Cornelius’ Dönnhoffs observation “When we plant in sandy soils or on sandstone, we plant vigerous rootstocks that will go deep as sandstone is very poor. I like it and some of very good vineyards such as Kastanienbusch has sand.

Loess is more difficult to control. It tends to give very opulent Rieslings and you have to be careful not to get overripe and boring wines. I have

to have a higher yield on loess and harvest early to maintain the acidity and freshness”.

The superpower sand is most frequently credited with, is its ability to withstand Phylloxera. It is not known exactly how, but most attributes it to the lack of organic matter as that is the common denominator between slate and sand and both are seemingly more or less phylloxera resistant.

There is too little for the louse to move- and live in and during rain showers the lice can’t keep their footing in such a quickly draining terroir.

Perhaps one of the greatest qualities of sand is its collaborative side. Effortlessly it merges with other soil types and plays a supporting role.

Its ability to slim a wine might be cherished more as we see an increase in warm vintages and the supple flagrancy of sand wines gains appreciation as the average consumer increase in sophistication.

Sand and Sandstone terroirs around the globe: Cornas, Moulin-a-Vent, Sardegna around Cagliari where many DOC are, Hérault, Colares (clay beneath), Châteauneufdu-Pape as one of the 9 soil types and likely second in importance to galets only, Champagne, Alsace (gres de vosges), Margaux, Nahe, Pfalz, Rheinhessen.

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M U D S TO N E M E TA M O R P H E D Schist, slate and gneiss are ancient, metamorphic rocks, typically 100s of millions years with mudstone as the prolite (starting material).

The definition of morphism can be deduced to the formation of new rocks by transforming an existing rock under pressure and temperature. This typically hap-

pens in great depths where the rock is recrystallized and new mineral crystals form in the process too hence, it is more than a transformation.

Often, we can see a foliation in the rocks and micas are grown in the process.

Micas are recognized by a ‘schistosity’ - a quality that makes them shimmer. With methamorphic rocks we can often see layers of minerals.

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The orientation of the layers reveals many geological facts as, when softened under pressure and temperature, it will always orient itself in the direction of easiest growth.

The orientation of the lines is called ’preferred orientation.

The higher the degree of metamorphism in general, the deeper below ground the soil was formed to get the pressure and temperature needed.

Slate is maybe the most widely used metamorphic stone in our daily life. Used for roofs, cutting boards etc. we can easily recognize it for its plate like texture.

It is, as the first metamorph of a mudstone, has a low degree of metamorphism, and the plate texture shows the preferred orientation. It can form really steep slopes with shallow soils and will naturally keep water out of the preferred orientation lines. The root of the vines can penetrate slate by growing opposite on the preferred orienta-

tion lines. Slate can commonly be found in Mosel, Galicia and Sierra Foothills as examples.

Schist is an increased metamorphic grade of slate. It has a more developed schistosity and a flakey foliation. It is larger grained and breaks down more easily. Schist is common in Anjou, Priorat, Duoro, Minho, Alentejo, Montalcino, Chianti Classico, Côte Rôtie, Beaujolais, Cederberg, Swartland, Barossa, Central Otago and western Sonoma.

Gneiss is a high grade of metamorphic rock and needs extreme conditions to be formed.

It is shaped just below the melting point of the rock which is expressed a distinct, goopy looking mineral color bands in the stone. Opposed to schist and slate, gneiss is remarkably hard and the soil is often blockier. Muscadet, Wachau and Galicia are places where gneiss can be found.

Prolites and their metamorph:

Sandstone ➙ Quartzite (extremely hard)

Mudstone ➙ Slate ➙ Schist ➙ Gneiss

Basalt ➙ Greenstone

Limestone ➙ Marble

Granite ➙ Foliated granite. So hard it can barely metamorphose.

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W W W.V I N F O R S Y N I N G . D K

To consider something a metamorphism the pressure and temperature must reach a certain minimum which only happens deep below ground.

As an example, a solidification of sand with the air squeezed out of it would be sandstone which is not a metamorphic rock. Resurfacing of metamorphosed material is actually rather unique for us to see and will only happen with massive tectonic activity. Most of our metamorphic rocks are older than limestone and originates from firstly the formation of Pangea 360-300million years ago followed by the ripping apart causing the metamorphic rocks to resurface. It includes Massif Central, Iberian Massif, Galician Massif, Massif Armorican (Loire) and Appalchian Mountains to mention some examples. Following the immediate logic, the protolith

is generally more common to find than their metamorphic version.

Minerality is a frequently used descriptor for a wine coming from schist and slate soil.

Brenna Quigley describes the wines as “Nervy and energetic” while Erni Loosen find the wines best described as having a “mineral driven acidity with a specific set of tertiary aromas. There are certain nuances repeated across styles.

And nowhere else in the world can you make a complete wine with just 7% alcohol”. Erni also wishes to underline that soil can never be a stand-alone factor: “Microclimate is most important. You can’t say that soil dominataed over steepness, exposure, sunlight hours etc. Mosel was 200 million years in the making between Hünsrück and Eiffel Moun-

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tains – this slate valley. At that time Mosel was south of equator where the sedimentation started on the seafloor but the tectonic activity compressed and heated everything to the Mosel we now have.”

According to Miguel Torres slate lowers the pH in wine: “It is a key factor for Priorat’s balance. We get balance from a place where it would seem impossible. It brings an element of nerve without taking anything away.”

Dirk Niepoort and Erni Loosen agrees that slate allows the roots to penetrate the soil and search deep for water and nutrients as slate it very low in organic matter. The steep slate hill sites are not useful for anything else but viticulture, but for this they are remarkable.

VO LCA N I C RO C K S Volcanic soils have an obvious origin and belong to the igneous rock family. What is less obvious is the categorization in accordance with the forming process and the molecular composition.

Ingenious rocks are formed from molten rock, and volcanic rocks are specifically from magma (molten rocks not yet erupted). Volcanic rocks however mean not only one thing.

There are many hundred volcanic rocks altogether forming ca 8% of the surface of the

earth. They are dynamic soil types often radically changing in intervals and weathers very easily.

Volcanic rocks are divided into different groups based on their silica, iron and magnesium content and weather they have erupted or not. If they erupt, the magma will cool above ground which will be more rapid than a cooling below ground. As a result, the crystals formed in the rock will be smaller. On the contrary we find plutonic rocks. They don’t erupt, rather they solidify into

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crystals below ground which takes substantially longer and forms large crystals.

Erupted rock types are categorized as extrusive, while non-erupted types are plutonic/intrusive. Both extrusive and plutonic rocks can be in the mafic end of the spectrum or the felsic end, mafic and felsic referring to the chemical composition of the rock. Mafic types have a higher melting point, an increased content of iron and magnesium, and low Silica while Felsic types have a lower melting point, low amount of Iron and Magnesium and are high in Silica. Mafic rocks have between 45-55% of silica, whereas felsic rocks have over 65% of silica, the highest of all rock types. The reason behind this distinguishment is that certain minerals will form earlier than others as a rock melt and they will crystallize out of the mass at dissimilar times from most mafic to least mafic. There are four categories: Ultramafic – Mafic – Intermediate – Felsic.

The Mafic rocks are dense, dark in color, very runny when molten. A volcano will empty these out on a regular basis and the lava will flow steadily on the ground. If an eruption can ever be peaceful the kind where Mafic magma erupts is.

Think of Hawaii or Etna where the locals are continuing their regular everyday life through times of volcanic activity.

Eruptions with felsic magma on the other hand, are violent!

They are recognized by a light

They are recognized by a light color and their explosive nature is due to the high silica content. A Felsic rock is less dense and more plastic in its texture. Eruptions of this kind is luckily rarer as evacuation from the area is necessary and oftentimes you will be able to see one side of the mountain completely blown up. Cascade mountains are of the Felsic kind.

One of the most well-known extrusive, mafic terroirs is the dark, porous basalt. Basaltic soils are often young soils only a few hundred years old coming from either a currently active volcano or a recently active one. They are slightly acidic to very acidic and often the pH of the wines are in an inversive relation to it, meaning that the wines have a high pH. Being mafic they will always be red/black in color and very iron rich. They are extremely heat and water retaining. These types of soil can be found in places like Etna, Willamette Valley (Eola Amity Hills, Dundee Hills), Canary Islands, Yarra Valley, Columbia Valley or The Rocks of Milton Freewater.

On the other end of the extrusive spectrum, we find the intermediate Andesite and the felsic Rhyolite. Increasingly light in color, less dense than the basaltic rocks. Rhyolite is less common than andesite and basalt. We can find Rhyolite and Andesite it in certain AVAs of Napa such as Stag’s Leap District, Spring Mountain District, St. Helena, Al-

sace, Tokaj, Santorini, Tasmania, Washington and Oregon.

N OT S O F E RT I L E Fertility is usually something we connect with volcanic soil yet, fertility is obtained over time when looking at a volcanic terroir.

A young volcanic soil is very infertile as there is virtually no organic matter in them and no clay. Volcanic soils weathers quickly down to form clay increasing their fertility. Thus, it is not naturally in the volcanic soils rather it is shaped into a fertile state, but their speedy breakdown had made them widely associated with fertile lands.

As eruptions occur between the formation of other soil types and in intervals during sedimentation, landslides etc. they can be blended into or packed in between other soils.

Anticipating where to find volcanic soils is simple: You just look at the distribution 43

of volcanos worldwide. Born from tectonic activity they draw their magma from huge chambers, called batholiths. It is no surprise that most of the volcanoes can be found on the borders of tectonic plates.

About the character of the volcanic terroirs John Szabo MS is one of the leading experts.

He underscores the fact that they quickly and easily decompose into something more fertile than desired which is one of the challenges. The dynamic nature of the soils also means there is little consistency in the records of them.

Dedicating years of his life to the volcanic wines he believe their trademark has something to do with the (positive) lack of something – always more difficult to describe that the presence of something: “Wines from volcanic regions are less fruity and more savory causing a salty sensation. This salinity we perceive as an inert freshness in the wines”.

T H E RA E XT R E M E traces of iron and sodium can be found in the

Santorini is a volcanic extreme. When it erupted 1620 BC it was a grand, felsic explosion – the most powerful eruption recorded on history ever with a power equivalent to that of two million Hiroshima atomic bombs changing the climate on earth for years! The island today is completely made up from tuff (Ash) and felsic rocks and is ranging as one of the poorest soils in the world. It is an extreme example where there is literally 0% clay in the soil. Perhaps the only terroir in the world where that it true it is a phylloxera free island too. Despite being a hot climate the wines of Santorini often reaches pH levels below 3 and

Apart from the already mentioned noteworthy Volcanic regions are: Côtes de Auvergne, Ahr, Nahe, Pfalz, Kaiserstuhl (Baden), Lake Balaton, Soave, Taurasi, Ischia, Campi de Flei-

wine – still unknown whether the latter comes from the sea sprays or the very low potassium content in the soils. The low potassium content in the soils of Santorini has a connection to the rainfall. During hydraulic stress the vine will concentrate the potassium in the grapes causing the pH to rise. As the vines are frequently water stressed on Santorini it is desirable for them to start with low levels of potassium to not loose to much acidity during the drought periods.

grei, Basilicata, Greco di Tufo, Madeira, Acores, Lanzarote, Maule, Itata, Malleco, Biobio, Eastern Sonoma, Geelong, Orange, Auckland, Gisborne.

While fair to say this signifies

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its existence in many wine regions worldwide, there are remarkably few volcanic terroirs in France.

G RA N I T E Granite defines many terroirs globally as it makes up most of the Earth’s continental crust.

Of volcanic origin and felsic nature, it is a plutonic/intrusive rock type. Most granite is formed by magma leaking out through channels on its way to surface through a volcano, crystallizing very slowly in the surrounding crust of the leaks (making it plutonic). Pushed to the surface either by tectonic activity or as volcanos die, the surrounding rocks and soil weather and erode to reveal these crystallized magma leaks which, once completely crystallized, is either Granite, Diorite, Gabbro or Peridotite depending on the felsic degree of the rock. Granite is felsic, Diorite is intermediate while Gabbro is mafic and the rare Peridotite is ultramafic. Deeper on the oceanic crust Gabbro is more common than the Granite we see in the earth crust – akin to Granite in being an intrusive volcanic rock, but mafic rather than felsic in

its composition. On the surface of the crust the mafic but extrusive Basalt can be found.

Granite is a well-defined and specific rock with a slightly acid nature. More uniform worldwide than limestone or clay for instance is, we also know it for its decorative purposes that has perhaps led our understanding of it astray. Despite being very defined in its chemical composition, many are mistaking non-granite to be granite as interior shops are often selling different rocks as the real thing.

Granite will always have a light grey base with salmon pink spots and feldspar that is peppered with ca 10% darker minerals such as biotite. The light grey is quartz while the salmon pink is potassium feldspar. Being felsic, the high silica content makes it extremely hard, rating as a 7/10 on the hardness scale where diamonds are 10. The hardness of it allows it to form dramatically steep hill sides. It has 46

low density, making it light, encouraging the surfacing of it during tectonic activity, playing a role in the high frequency of granite.

Due to its hardness Granite has low permeability. After surfacing, it is common to see the granite fracture, as it doesn’t give in to the surroundings, due to its hardness, it cracks under continued pressure and weathering. As it weathers it becomes shallow and gains permeability. Most granites are extremely old and shallow.

After fractioning it likewise builds a strong permeability called a secondary permeability. Fracturing also leaves space for the granite to initiate its process towards weathering down to clay particles. In the process the clay and granite doesn’t mix hence, there is for instance no granite equivalent to marl. Places where the granite doesn’t fracture can be recognized by softly rounded patterns and shapes as we know from Beaujolais as opposed to pointy and edged hills.

Granite is to a large extend defined by the virtual absence of clay. Normally the clay content range among the lowest of any soil type which is a good thing in this incident Because when granite weathers it does not form the desired clay type.

On the contrary the weathering of granite will directly from kaolinite! Something Pedro Parra is not fan of, despite liking granite overall. He has experience working on granite soil with the guys from Commando G. It taught him a great deal about how to approach non-clay terroirs: “Gredos has very decomposed soils due to the many years of weathering of the Iberian Massif. The Massif is very old. The best vineyards here all have similar, very pure granite. How you interpret non-clay terroirs in the cellar is something else.

You can’t do it Burgundy style.

They asked me at Commando g why I was doing it that way? Taking Burgundy here?

Granite is so different to what Burgundy is. I changed completely how I make my wines from then on. Granite drains quickly and easily dries out the tannins in a wine. If you then apply modern techniques with extraction and structure, you get rustic wines. It made me think. Many of the best winemakers in Rhône study in Burgundy and try to then vinify their Rhône wines like that.

But they can’t. Granite is acidic, not alkaline.”

The lack of clay makes granite a very poor, nutritionally weak soil forcing the roots to search deep for water. This makes cultivation on granite challenging, especially if you have younger vines. There is no surplus for cultivating cover crops and the vineyard management must be very precise. But the best granitic terroirs make it worth it. Kermit Lynch speaks of an extra degree of purity, precision and minerality in granite

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wines and he is not alone in describing wines from granite as bright. Looking at the terroirs famed for granite there is a unison between the observation of precision, energy and brightness, Parras wisdom of difficulties understanding to work the terroir and the wines being made from these rocks.

The best of them certainly has that perfume and inert drive, such as we know it from the top Gredos, best Beaujolais or most elegant Northern Rhône wines.

Classic granitic terroirs include among many others: Northern Rhône, Massif Central, Beaujolais, Western Australia, Bendigo, Paarl, Stellenbosch, Darling, Cape Town, Itata a range of Alsace Grand Crus (Schlossberg, Wineck-Schlossberg, Sommerberg, Frankstein, Kaefferkops, Praelatenberg, Gloecksberg to mention some), Hermitage (only the upper part of the western hill while the middleslope is limestone and silt and sand is at the bottom), Condrieu, Cornas, St. Joseph, Château Grillet, Roussillon, Pais Nantais (also Gabbro), Corsica, Sardenia, Gredos, Rias Baixas, Ribera Sacra, Mencao & Melgaco sub in Vinho Verde.

G RAV E L S & P E B B E L S Sounding like the title of a 70’ies rock band gravels and pebbles are some of the most talked about terroirs. Tangible as we often see them on the surface, gravels and rolled pebble terraces represent a major group of transported terroirs.

These terroirs support some of the world’s greatest vineyards everywhere from Bordeaux to Napa Valley. Formed from rivers, alluvial fans, and even glaciers the rocky presence in the vineyard often correlat-

ed with that mysterious term; minerality.

Gravels and pebbles are larger than 2mm and easily visible to the naked eye and touch.

They form from weathering of already existing rocks and the grain size and shape tells a story of its travel. Large size of grains comes from high energy transportation as more energy is needed to carry the weight.

The longer a gravel has been underway, the more rounded it becomes as the travel beats 48

off and rounds the edges on it. The sorting of the gravels relates to the transport form and gives a clue of the original source. Alluvial types of gravel will often display a more homogenous character than say glacial or colluvial. From the composition of a transported soil, geologists can often read the dispositional environment – was a big flooding the cause of it ending up here? A landslide? A long travel by river?

Glacial activity?

Transported Soil: A soil that forms from unconsolidated material that overlies intact bedrock.

This unconsolidated material was transported to its final location by either water, wind, ice, or gravity. The soils that form from these materials can be derived from many different types of rocks and sediments.

portation of materials by gravity, such as at the base of a steep slope. Colluvial materials are typically very angular as they have not traveled far from their source.

Glacial: are environments that produce many complex deposits as glaciers scour the land in their advance, and then dump it out (along with meltwater) on their retreat. These deposits are typically poorly sorted. Gravel and terraced terroirs are known for their significant percentage of rocks, which result in a welldraining soil that retains heat. Glacial activity can carve deep into the bedrock and pick up material from it.

These soils are often deep with low fertility.

Alluvial, Fluvial, Colluvial and Glacial Terroirs Alluvial/Fluvial: These terms describe transportation of materials by water and are typically related to rivers. Fluvial is used specifically for river deposits, whereas alluvial is a more general term that can apply to environments near rivers such as floodplains and alluvial fans. Alluvial environments erode material in a main river channel, but also deposit materials during large storm events. This process forms a series of terraces of various ages and compositions.

Compositions of these terraces vary from very cobbly, well-draining terraces, to sandy banks, and even clay-rich pockets.

Aeolian: Term referring to transportation by wind. More common to see with sand than gravel due to the weight of gravel.

Residual soil: Can be gravel too but has not been transported, rather it is eroded from existing rock.

Colluvial: This term is used to describe trans-

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Alluvial fan in the making.

F A N S A N D VO M I T When we talk of transported terroirs, terraces refer to the period in which a specific sector was formed and of what it is composed. Terraces develop as rivers are constantly eroding material away and their water level change, deposit-

ing material in the process.

On the floodplains water will deposit material on the rare occasions of overflooding.

The terraces might look very different to each other even a few meters apart as a river has different energy distribution throughout the course of 52

its flow, impacting what type of gravels it can move. Often terroir “pockets” form alongside a river which can be considered isolated terraces. Jane Anson’s inside Bordeaux sheds great light over the complexity of terraces, providing detailed maps clearly displaying

micro terroirs. The complexity increases if fluvial deposits are mixed with those from an alluvial fan, adding deposits travelled from the mountains to the mix. Such is the case for instance in Napa Valley where alluvial fans from Mayacamas range is all the talk in Rutherford and Oakville.

Glacial soils is another story. They are less uniform, less sorted and not shaped much by their transportation. Classic glacial moraine soils are a chaotic mix of materials. Pedro Parra equates a glacier to a stomach and a moraine to the stomach’s mouth. He says that moraines are “zones of vomit” containing “all the food the glacier has been eating, completely muddled and semi-digested”.

Semi-digested vomit terroir is perhaps not what most sommeliers and winemakers have in mind when they look at the high esteem, quality, and price tag the wines from the most famed glacially formed region carry: Bordeaux. Andrew Jeffords elaborates on the creation of the Bordelaise terraces: “No river gravels, though, are more famous than those of Bordeaux. In essence, Bordeaux’s celebrated gravel banks are the creation of the Ice Ages of the last 2.5 million years. During the frozen periods, sea levels and river levels dropped by 100 metres or more. Much of the land surface was locked in icy tundra. During warming periods,

ice melted, and sea levels rose and reclaimed the land once again. Modern glaciology has revealed that there were up to 50 of these glacial cycles rather than the classic four glacial stages – Günz, Mindel, Riss and Würm. The last glacial maximum was just 22,000 years ago. Clearly, the time periods over which all of this took place were significant.

The entire cycle happened repeatedly. This incessant sluicing to and fro of water is what has created the huge quantities of water-rounded gravels found in the Médoc, deposited in a series of different terraces. The gravels mostly occupy left-bank zones, notably in the Médoc communes of Saint-Estèphe, Pauillac, Saint-Julien, Margaux, Listrac and Moulis, as well as Pessac-Léognan, Graves and Sauternes. There are also some gravel zones on the right-bank, too, in Pomerol and Lalande de Pomerol, and some parts of Saint-Emilion.

These stones come from the Massif Central, the Pyrenees or their intermediate zones, but that origin is irrelevant. What matters for the vines is their physical structure, together with the structure of the soil layers -- and the quality of sub surface sands and clays slowly created within these gravels. In contrast to Bordeaux’s gravels, the origin of the extraordinary pebble terraces of the Southern Rhône is not exclusively glacial.”

In younger landscapes adjacent to mountain ranges we 53

find the highest frequency of gravel and pebbles. Naturally many of them are of colluvial character but also fluvial fans and alluvial deposits are regularly encountered. Initially we might have associated gravelly soils with viticulture simply because most other agricultural produce can’t grow on gravel. But the vine needing a well-drained topsoil on a more nourishing subsoil, can find a great home in such conditions.

The extremity of gravel soils might be misinterpreted at times, as it certainly looks like the gravel continues deep down. The roots of the vines will encounter organic- and finer material, but it is washed down in between the pebbles and gravels. These hidden depths can and will include sand, silt and clay, which are common to almost every vineyard environment. And exactly what you find beneath the gravel or pebbles will be crucial to the potential greatness of the terroir. Clay and limestone are important partners to gravel provided the necessary fertility and water storage and those are the exact foundations upon which the greatest of Bordeaux gravels rest.

STAT U E S QU E S O UL Most gravel and rolled pebble vineyards are very gently undulating, as in the Médoc, or flat and plateau-like, as in Southern Rhône. In certain circumstances, this can mean that they are frost-prone as they lack the natural air drainage that occurs on slopes.

At the same time they are great captivators of heat during the growing seasons retaining it overnight where the vines receive it enabling a wider selection of varietals to ripen.

Stephane Derenoncourt comments: “Gravel is special and was selected first for its ability to ripen. In terms of terroir of course there is something singular. You have a micro burning of the grapes from the reflection of heat from the gravel to the grapes which can give some smokey flavors. But it is important that there is clay underneath. It gives the power in the wine ad withholds the water. You have clay with limestone underneath the gravel on the best vineyards.

Limestone gives aromas and perfume. It has effect in the mouthfeel too and change the quality of the tannins so you can have balance between the powerful fruit from clay with the elegance and lightness. If you consider only the gravel part you will not understand this. In terms of taste you need to consider many things: The % of sand, the % of clay and which quality of clay you have.” Louis Barroul agrees and adds: “If you want to talk about soil you have to cinsider what is underneath because that is where the chemical ex-

change is. If you talk about the stone it is only the physical part you talk about. Where you have too dee a layer of pebble it will always be a fight to get good wine. You will always loose the battle. You need an equilibrium between stone and soil below and depth of pebbles.Where you have pebbles or gravel you don’t easily get botrytis because of it’s dry and warm surface. This gives you clarity and precision That to me is one of the signatures of pebbles and gravels” Steve Smith MW (founder of Craggy Range and owner of Pyramid Valley) contributes their success to ripen Cabernet in Gimblett Gravels to the gravel: “We have a climate not unlike that of Bordeaux but slightly cooler. Gimblett Gravels is the most stony place in New Zealand. It is likely the only place here with enough sunlight and heat to ripen these varietals. (…) In the wines you can find a gravelly texture. Obviously with young vines they are dominated by the fruit but certainly with older vines there is a stony character to them.

With Sauvignon and Chardonnay we see a texture and withdrawn fruit; you can get sort of a steely character, and with red we can find a marked tannin and structure.”

Seemingly in right proportions gravels and pebble are the components to lift a wine from good to great providing the stature and tension needed to compliment a bigger structure or intense fragrance. It will remain a soil type difficult to recognize from the surface alone 54

serving as a great metaphor of what wine making perhaps is about: Balance, patience and in depth understanding.

Other regions signified by gravel and rolled pebbles: There are many especially in Europe. Basically wherever there is a current of former river of significance gravel or rolled pebble is likely to be found. Jurançon, Savoie, Ontario, Niagara Peninsula and Finger Lakes, Washington States, Okanagan Valley are all of glacial origin.

There are a number of gravel sites in Loire, often supported by sand, such as Chinon and Bourgueil.

Cahors, Gaillac, Rioja, Chile, Mendoza, Gimblett Gravels (the Gimblett Gravels were deposited as recent as in 1867 during a massive flood), Marlborough and many others.

Often the appellation name allude to this such as Grave del Friuli or Graves.

Winegrowing in Austraia, South Africa and America is generally on more weathered, eroded and ol-der soils, meaning gravel and pebble would tend to have weathered down.