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Product Details
| ISBN-13: | 9780226177229 |
|---|---|
| Publisher: | University of Chicago Press |
| Publication date: | 11/08/2019 |
| Edition description: | First Edition |
| Pages: | 216 |
| Sales rank: | 1,138,368 |
| Product dimensions: | 6.20(w) x 9.10(h) x 1.10(d) |
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CHAPTER 1
Volcanoes and Wine
The notion of terroir — a sense of place — applies particularly well to volcanoes. These towering landforms have specific bedrock and soil, locally influence the climate, and offer a range of orientations and elevations to fit a multitude of crops.
The Earth is a showcase planet when it comes to volcanism. On any one day, approximately twenty volcanoes are erupting across the globe. The aggregate number of active volcanoes rises to sixty over the course of one year and totals six hundred across recorded history — that is, the past 2,500 years.
Our civilization is affected by volcanism in many ways, with some eruptions taking their toll of human lives, and others altering the climate on timescales of a few weeks or a few years. But the greatest consequence of volcanism might well be the creation of new landscapes, new minerals, and ultimately new soil. This is where plant life and agriculture fit into the picture.
Volcanic eruptions provide a range of chemical elements used by plants, both in solid and in gaseous form. Gases include the water vapor, carbon dioxide, and sulfur dioxide that volcanoes constantly expel into the atmosphere. Carbon and, to a lesser degree, sulfur are among the most important elements in the building blocks of life, such as amino acids and proteins. As for the elements distributed by eruptions in solid form, these include silicon, phosphorus, and a whole range of metals, such as calcium, sodium, potassium, iron, magnesium, aluminum, manganese, and other trace elements.
Locked inside lava flows and the fallout that rains from ash clouds, these solid elements need to be freed from their mineral cages in order for life-forms to absorb them — a breakdown process made possible by Earth's efficient water cycle, as well as by a vast chain of chemical and biochemical reactions.
Volcanoes and Agriculture
The role of liquid water in breaking down minerals and feeding plant life is one reason volcanoes are so important in agriculture. Their bulging masses create obstacles that deflect air currents. When a batch of humid air rises along the slope of a volcano, its temperature drops: water condenses and rains out onto the windward side of the obstacle, and dry air blows down the opposite lee side.
The windward, rainy side of a volcano is a haven for water-dependent plants, including a variety of crops like rice, fruits, and vegetables, but the dry lee side is also profitable for a whole range of crops that instead need little water and a maximum amount of sunshine, such as coffee, nuts, and grapes.
One prime example of this is just east of Naples, at Mount Vesuvius: Italy's most famous volcano. As described in its dedicated chapter, Vesuvius has long been the fruit basket of Italy, and despite increased competition from Europe's Common Market, the volcano still provides to this day the majority of the country's apricots, as well as its most prized tomatoes and cherries. The role of the volcanic landform is apparent when mapping precipitation and crop types: prevailing north winds focus rainfall on the northern side of the volcano, where most cherry trees are planted. The western sector gets moderate rainfall and enough sun to support apricot trees and tomato crops, whereas the dry southern and southeastern flanks — above Herculaneum and Pompeii — bear vineyards that need minimal water.
Mount Etna in Sicily is another good example of the role of orientation on a volcano, and of elevation as well: a sizable peak provides a wide range of altitudes, which translates into different climates at each level. Mount Etna thus possesses a low-elevation, hot agricultural belt for its prized oranges and citrus fruit, as well as an upper, cooler vineyard zone between 450 and 1,000 meters elevation (1,500–3,300 ft.): the cool nights, typical of the highest reaches, slow down the ripening cycle of the grapes and promote the formation of complex aromatic molecules, yielding quality wines that are now recognized worldwide. At the highest reaches of its northern flank, the volcano even harbors alpine birch and pine forests — an exceptional sight in Sicily — that were long harvested for timber and fuel wood.
Mount Etna's freestanding cone also provides a whole gamut of wind and rain exposure. Orange groves are located in the sunniest southwestern and southern sectors, whereas vineyards occupy the eastern half of the volcano, because morning sunlight is necessary to dry out any nighttime or dawn precipitation that might carry molds or other vine-threatening diseases. Even the northern sector of Mount Etna offers agricultural niches: in particular, the extra moisture carried by the northwestern prevailing winds benefit pistachio trees — a crop that reaches world-class excellence around the city of Bronte.
An interesting aside is that volcanoes can alter the regional climate when they erupt, which can significantly affect the characteristics of that year's vintage. A case in point is the May 1980 eruption of Mount St. Helens, in Washington State, which chilled the spring climate that year in the downwind Oregon estates to the point that the state's 1980 Pinot Noir won two gold medals in 1982 for the first time and was favorably reviewed in the New York Times.
Volcano Types and Eruptions
Besides the range of orientations and altitudes they provide to crops, and their local effect on climate, volcanoes come in many different types and forms, and also display a diversity of eruption styles that dictate the type of substrate — rock texture and soil chemistry — available for agriculture.
Volcanism is the process by which a hot planet gets rid of its heat. A planet like the Earth is partially molten inside. There is a dense iron core at the center, with a solid inner part — due to extraordinary pressure — and a liquid outer part (with a temperature around 4,000°C, or 7,000°F). This molten iron never reaches the surface and does not take part in volcanism. Above the iron, starting at a depth of approximately 3,000 kilometers (1,800 mi.), and stretching almost up to the surface, is a mineral paste known as the mantle. It also contains iron, but mostly silicon and magnesium, as well as calcium and aluminum, and other metals in small amounts, all bound into interlocked crystals by a great deal of oxygen. There are also minute amounts of volatile molecules dissolved in the mantle, principally water, carbon, and sulfur oxides. The temperature ranges from 4,000°C at the bottom of the mantle to about 1,000°C at the top (7,000°F–1,700°F), hot enough for the mineral paste to flow and circle in great loops, like molasses on a stove, but at a very slow rate: a couple of centimeters (about an inch) per year.
Above the churning mantle lies a lid of cooled, rigid "scum": the Earth's crust. Only 5 to 50 kilometers thick (3 to 30 mi.), depending on the location, the crust is the result of countless volcanic eruptions that tapped the upper mantle over billions of years to coat the surface of the planet with flows of molten rock that chill into place: the icing on the cake.
Volcanism is therefore the process that moves fluid mantle material to the surface. It does not occur everywhere: the mantle is very hot but rarely hot enough to melt and send streams of liquid rock upward. Exceptional places where the mantle is hotter than average and where volcanism does occur are known as hot spots. Dilated by the extra heat, the mineral paste ascends toward the surface, in the same way that a hot-air balloon rises through cooler air. Moreover, as pressure declines on the way to the surface, the hot, buoyant rock begins to melt. This is similar to taking a kettle of hot water up a mountain: the pressure drop causes the water to boil.
As the rising blob of hot rock impinges on the Earth's crust, it causes it to bulge and fracture: the melt then rushes through the fissures and erupts at the surface. At first, the molten rock, known as magma, can contain a lot of dissolved gas that makes it fizz, like a soda bottle opened for the first time: the magma sprays skyward in the form of a lava fountain, also known as a Hawaiian eruption, in reference to the most famous hot spot on Earth that created the Hawaiian Islands. After most gas is flushed out, the magma simply oozes out of its fissure or crater and proceeds downslope as a peaceful lava flow.
In hot-spot settings, minerals come from great depth in the mantle and have a metal-rich chemistry that makes the resulting lava particularly fluid: flows cover great distances and build shallow-sloped shield volcanoes. In view of the large volumes of magma pumped up by hot spots, such shields can reach impressive sizes and elevations. Hawaii's Mauna Loa volcano holds the record of the largest volcano on Earth, with an estimated volume of 75,000 cubic kilometers (18,000 cu. mi.) and an elevation of 9,170 meters (30,085 ft.) above the seafloor.
Another setting for volcanism on Earth is provided by shallow convection loops of the upper mantle that act like the rollers of a conveyor belt and tear the crust apart into great segments, or plates, that move relative to each other — this is the slow ballet of plate tectonics. Where two plates move apart, magma rises at the seams and pastes new volcanic crust along their boundaries: such locations are known as rift zones and often develop in oceanic settings, deep under water (mid-ocean ridges). Hence, they are rarely associated with agriculture, or with wine making for that matter.
Other plate margins have not experienced a hot-rock pasting for a while, and they have cooled, contracted, and densified to the point that one plate flexes downward (creating a topographic trench) to slide under its neighbor and sink back into the mantle: a process known as subduction. During this process, the sinking slab heats up and expels water vapor and other fluids that then work their way back up through the overlying hot mantle. Because the injection of fluid into hot rock is one mechanism that can cause rock to melt, this often generates magma, which ascends to build a chain of volcanoes behind the subduction trench. Examples include the Cascades range in the states of Washington and Oregon; the volcanoes of Central America and of the South American Andes; Mount Vesuvius and other volcanic landforms along the coast of Italy; and Indonesia, the Philippines, and Japan, along the Pacific Ring of Fire.
Subduction volcanoes often host explosive eruptions because of the quantity of volatiles — principally water vapor — that end up in the erupting magma. Water also affects the type of magma generated, promoting a high proportion of silica in the brew and making it particularly viscous. The combined effect of high volatile content and viscosity blows the magma apart as it rushes up the volcano's chimney: jets of fragmented magma — particles named pyroclasts by geologists — billow skyward to form dense clouds, or plumes, that drop their content downwind of the craters. Such outbursts are Plinian eruptions, in reference to the famous eruption of Mount Vesuvius in AD 79 described by Pliny the Younger.
The fallout particles, which are often ridden with holes by the escaping gases, bear different names depending on their porosity — very porous ones are pumice — and on their size, for example, ash when they are fine, lapilli or scoriae when they are the size of a nut, and blocks or bombs when they are the size of a fist or larger.
Finally, the fallout can take on a catastrophic form when the pyroclasts expelled by the eruption build up such a dense column in the atmosphere above the crater that it collapses under its own weight and rolls over the landscape like an airborne tsunami: such pyroclastic flows can level and blanket entire towns, as they did Pompeii and Herculaneum in AD 79, and more recently Saint-Pierre in Martinique in 1902.
Volcanic Soil
With so many different geological settings and eruption styles, it is no wonder volcanic terrain comes in a variety of textures and profiles, adapted to various degrees to agriculture and vine growing. Some lava flows are hard and unbroken and require working over with crowbars and bulldozers, or centuries of erosion, to become farmable. Pumice and ash fallen from the air, however, are readily tillable. Both often occur together on the same site: trenches and cross-sections through volcanic fields frequently show piles of lava flows interspersed with layers of ash fall.
Besides ground texture, the chemical makeup of lava and ash naturally affects agriculture. Some elements brought up from the mantle by volcanic eruptions are particularly valuable to plant life and enrich the soil. Boron, for example, plays a fundamental role in cell division and influences flowering and fruit set, thus directly affecting crop yield. Potassium is extremely important in regulating sugar and acid content — a role it plays in grape juice and wine in particular.
On somewhat aged soils, on which crops have been grown and rotated over centuries, these elements have already been soaked up by countless plants and removed from the land. For new crops to receive their proper share, the soil needs to be spiked anew with mineral nutrients, and repetitive eruptions are a great way to do so. Compared to lava flows, which might take decades or centuries to break down sufficiently to provide these precious elements to crops, explosive, gas-rich eruptions are particularly efficient in doing the job. The material not only is blown to bits by the expanding gases but also can be sprayed far and wide, covering large areas. If the output is diluted, it can shower existing crops and reach the soil without harming the vegetation. Too thick an ash cover, however, can choke the plants, as is often the case on the flanks of Indonesian volcanoes.
The big advantage of ash fall is that its minute particles offer a greater surface-to-volume ratio than large blocks, facilitating their interaction with water, bacteria, fungi, and other agents capable of breaking down the volcanic minerals to free up their elements. Leaching by rain and runoff water works best if the water is slightly acidic, as is often the case on volcanoes: erupting plumes provide sulfur that combines with water to form sulfuric acid and with carbon to form carbonic acid.
The process is all the faster if the starting material is poorly crystalline and glass-rich, which is typical of airborne ash. Once the ash is mixed with organic-rich humus already present on the ground — from the decomposition of previous plant life — the result is a rich volcanic soil. Volcanic soil, known as Andisol, constitutes one of the thirty or so major soil groups recognized by geologists.
Andisols are usually fluffy and of low density, and thus easy to plow. There are even cases of volcanic soil being shifted from place to place to support agriculture, such as in the Canary Islands, where volcanic cones are mined for the material, which is then loaded on trucks and spread in the lowlands to grow a variety of crops, like beans and potatoes.
Volcanic soils also have drawbacks, however. They are easy to disturb, can be washed away by floods, and can even fail in dramatic landslides, as happened at Sarno, near Naples, where in 1998 a slope failure claimed 161 lives. Mudflows can also rush down gullies in the wake of water-rich eruptions and run over entire towns, pooling and setting like concrete.
However, by and large, volcanic soil is a precious, fertile substrate for agriculture. Andisols support coffee and tea crops, maize, rice and potatoes, tobacco, and fruits and vegetables as a whole. Grapevines and wine, the main topic of this book, are rarely cited in that list, though, and for good reason: grapes are mostly grown outside tropical regions, where most active volcanoes are located. In the wine belts of temperate regions, the substrate is most often limestone and sandstone, granite and schist, gravel and sand, with little soil. But when there is a match in these temperate zones between volcanoes and vineyards — the examples explored in this book — the result is often spectacular.
VOLCANOES AND GLOBAL WARMING
Global warming is a fast-paced, troublesome evolution of the worldwide climate that has a direct impact on agriculture. The rise in temperature and the change in precipitation patterns are so rapid that farmers and vine growers need to plan medium- and even short-term adjustments for their crops.
With coffee as an example, rising temperature and precipitation changes are directly threatening plantations for two reasons. A hotter environment is detrimental to the health of the plant and the quality of its coffee beans. Also, many pests and fungi thrive at higher temperatures and follow the temperature rise upslope to infest the crops. In Tanzania, for instance, the nasty coffee-berry borer H. hampei has climbed 300 meters (1,000 ft.) in ten years.
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Table of Contents
Preface 1 Volcanoes and WineVolcanoes and Agriculture Volcano Types and Eruptions Volcanic SoilVolcanoes and Global Warming Volcanoes and Wine 2 Santorini
The Dawn of Wine Making Sitting on a Time Bomb An Eruption of Mythic Proportions Renaissance and Vinsanto Santorini in the Twentieth Century Santorini Grapes Wine and Climate A Terroir Made of Pumice A Variety of WinesGuide Section: Visiting Santorini 3 Mount Vesuvius
The Bay of Naples The Vineyards of Pompeii The Fatal Eruption of AD 79 The Final BlowPompeii’s Burial Date Revisited A Vineyard Rises from the Ashes Vesuvius Grapes and TerroirMount Vesuvius: Tectonic Setting and Magma Composition Italy’s Orchard Lacryma Christi: Tears of Christ Living Dangerously Farming the Last Lava Flow A Look to the FutureGuide Section: The Practical Guide to Touring Mount Vesuvius 4 Mount Etna
Sicily’s Garden of Eden Europe’s Most Active Volcano Playing with Fire
The 1991-1993 Eruption
A Train Ride around Mount Etna Etna’s PistachiosThe Oranges of Mount Etna Strawberries and Wine A Brief History of Wine Etna Grape VarietiesI Vigneri, Keepers of Tradition The Wines of EtnaEtna’s Fruit Brandies The Winemakers The Notion of TerroirFranchetti’s Suite of “Terroir” Wines A Very Special VineyardGuide Section: Visiting Mount Etna 5 The Aeolian Islands
Malvasia: Nectar of the Gods Vulcano: Vines on a Time Bomb Lipari: The Central Hub Stromboli: Fire and Wine Salina: The Hub of MalvasiaPantelleriaGuide Section: The Practical Guide to the Aeolian Islands 6 France’s Hidden Volcanoes
Rift Zones in FranceA Volcano in Provence Vines Rooted in HistoryGrapes of Auvergne The Comeback of Côtes-d’Auvergne Fire Meets Water: The Châteaugay Terroir The Hill of CorentBoudes, Chanturgue, and Madargue Wine and Pumice: The Neschers TerroirGuide Section: The Practical Guide to Auvergne 7 The Canary Islands
Vineyard History and Distribution Lanzarote and the 1730 Eruption Holes in the Ash Grape Varieties in the CanariesThe Azores Islands Canary WinesGuide Section: The Practical Guide to the Canary Islands 8 California, Oregon, and Hawaii
Napa Valley: A Tectonic Basin A Mosaic of Terroirs Oregon’s Great Lava Fields A Mighty Flood Willamette Valley and Pinot Noir Ocean versus Lava: Pinot Noir Takes the Stand Hawaii and CoffeeWines of HawaiiGuide Section: Visiting California and Oregon Notes Bibliography List of Websites Credits Index