Confusion Corner: Tuff, Tufa, Tuffeau

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Tuff, tufa, tuffeau: welcome to confusion corner.

These “three t’s” are all types of stone and/or soil. Two—tuff and tuffeau—are of particular interest to viticulture, while tufa is the odd man out.

Let’s take a closer look:

Tuff: Tuff (pronounced tuhf like the English word tough) is a type of volcanic soil; however, it is sometimes classified as a sedimentary soil—so let’s just say it is formed via both volcanism and sedimentation.

Tuff is created when molten lava blasts out of a volcano, cools and fragments as it floats through the air, and eventually lands in a heap upon the ground. With time, the fragments (including volcanic ash as well as bits of igneous rock) settle, condense, and cement together into a soft, porous stone.

Tuff soils inside the crater of Mount Vesuvius (photo credit: Simona Cerrato via Wikimedia Commons)

Tuff-based soils are found in Napa (Howell Mountain), Lake County (California), Madeira, Hungary (Tokaj), Alto Piemonte (Gattinara, Ghemme), Campania (Mount Vesuvius) and large swaths of Yellowstone Park.

Tuffeau: Tuffeau (pronounced too’-foo) is a local type of limestone found in the Loire Valley. Tuffeau is fine-grained and very low density (about half the density of granite). Tuffeau is formed from the remnants of the sea floor (sediment, fossilized sea creatures, and sand) that covered the Loire Valley over 90 million years ago. Over the millennia, these particles became compressed to form a unique type of limestone due to the presence of foraminifera (creatures with multi-chambered shells), and the (previously) shallow water that stood between 2 and 20 meters deep—other forms of limestone were formed under deeper waters.

The fortified wall at the 8th-centure Château de Loches, showing tuffeau blocks of various ages (photo credit: Valerius Tygart via Wikimedia Commons)

Weathered tuffeau, combined with sand, flint, and clay—as found in the Central Loire regions of Anjou, Saumur, Touraine—is an excellent vineyard soil. Tuffeau is equally famous for being the building blocks of many of the gorgeous castles of the Loire, and may also be known as Turonian Limestone (after the city of Tours).

Tufa: The words “tufa” (pronounced too’-fah) and “tuff” and commonly confused, and that’s ok for people having casual conversations about the ground beneath their feet. However, for geologists and wine geeks, there’s a big difference between the two (and, to make matters worse, tufa and tuffeau have more in common than tuff and tufa). So here goes: tufa is a rare is a rare type of limestone created when calcium carbonate-saturated water releases carbon dioxide and precipitates a soft, caclium-carbonate rock. Tufa is specifically formed in ambient-temperature water.

The best-known examples of tufa (in the fascinating form of tufa towers) can be found at Mono Lake, California. Tufa is not—to the best of my knowledge—a factor in vineyard soils.

Tufa deposits originating from hot springs are known as travertine—and that’s a whole other corner story.

References/for more information:

• Feiring, Alice (2017) The Dirty Guide to Wine. New York: The Countryman Press.
• Franzmeier, Donald, William McFee, John Graveel, and Helmut Kohnke (2016). Soil Science Simplified, 5th edition. Long Grove, Illinois: Waveland Press.
• Robinson, Jancis and Julia Harding: The Oxford Companion to Wine, 4th Edition. Oxford, 2015: The Oxford University Press.
• USDA Soil Survey/National Resources Conservation Service: http://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/survey/
• Soil Science Society of America: https://www.soils.org/
• https://www.monolake.org/about/geotufa
• https://www.britannica.com/science/tuff

The Bubbly Professor is “Miss Jane” Nickles of Austin, Texas… missjane@prodigy.net