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Striking Wines from California's Volcanic Lake County
By Rebecca Murphy
Aug 11, 2022
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The wine country of Lake County is located in the California coastal range, north of Napa and Sonoma and east of Mendocino County.  “It is a geographic, geological oddity created by volcanic activity that is still going on underground.  At 4,300 feet, Mount Konocti towers over Clear Lake, which is second largest body of fresh water in the state.” This was among the interesting facts emerging from a seminar hosted by Jim Gordon of Wine Enthusiast earlier this year.  Volcanic wines have become a hot topic in the wine world.  Canada’s first Master Sommelier, John Szabo, who wrote Volcanic Wines:  Salt, Grit and Power was also among the speakers.  Peter Molnar, co-founder of Obsidian Wine Company, and Joy Merrilees, Vice President of Production at Shannon Family of Wines, provided first-hand accounts of the challenges and joys of making wines grown in volcanic soils.

We learned from Gordon that the last major volcanic eruption in Lake County was only 11,000 years ago, recent in geologic time.  The U.S. Geological Survey currently ranks the Clear Lake volcanic field as the thirty-third most dangerous volcanic site in the country—out of 161 contenders.  The 9,500 acres of vines in Lake County are growing mostly at elevations situated between Clear Lake’s 1,370 feet and extending up to 2,600 feet.  The soils in which the vines are planted include three types:  Land formed from cool-hardened lava, alluvial soils, and explosively ejected rock and settling ash.  Although Lake County is only one county removed from the Pacific Coast, it has a climate more like that of the Sierra Foothills, which are much farther inland.  

Szabo gave us a tutorial on volcanic wines, explaining that there is no official volcanic wine category, but a loose collection of wines that happen to come from volcanic regions all over the world.  “When I first tried to pitch this idea to editors, they all came back saying volcanic wines are a ‘niche category.’  Made me chuckle.  In fact, it covers an amazing stretch of the world of wine, different grape varieties, and different climates.”  Actually, it has become an unofficial category of its own.  Szabo’s definition of volcanic wines is simply this:  A wine that is grown on soil derived from volcanic material, basically including all the stuff that got spat out, erupted from, or oozed out of the earth at some point.  So, this so-called niche category of volcanic wines grows out of a pretty broad range of soil types.

Szabo suggested, “let’s have a quick look at where volcanos happen.  The earth is composed of several different tectonic plates, and those plates are constantly moving and jostling, which means that they are either bumping into one another or moving apart from one another.  The vast majority of volcanism occurs on plate boundaries and plate margins.    Another type of volcanism is called ‘hot spot volcanism.’  An example is provided by the Hawaiian Islands, situated smack in the middle of the Pacific Plate.  They are not on a plate boundary but came from an upwelling of superhot magma underneath that forces its way through the plate.”

Other volcanic areas that support vineyards include the Canary Islands off the coast of Africa and the Azores in the mid-Atlantic.  In Europe, the Rhine Valley, Alsace and parts of Germany qualify as little volcanic hot spots. Then there’s the Pacific Rim running from New Zealand through the tip of Chile and up through the western boundary of the Americas to British Columbia.  All these areas have experienced significant volcanic activity.  

Apparently, the California Coast is seismically active because of three plates called the triple junction.  Szabo explained that the Pacific plate is sliding up into the Juan de Fuqua plate, which is sliding into the North American plate.  This grinding started about a 25 million years ago around San Diego, and has been moving slowly northward, which explains the progression of volcanics in California, starting with the creation of the Sierra Nevadas.  Lake County is a very active area in northern California.  Mt. Konocti erupted 11,000 years ago, a blink of an eye geologically, but the progression of volcanics has gone on much longer.

Lake County has some of the youngest soils and some of oldest soils in northern California, a mixture of different types of volcanic rock.  However, Lake County has something unique, namely, black glass obsidian, which comes from a very explosive eruption of a type of lava called rhyolite.

Szabo goes on to note that, “Lava is classified along a continuum determined by its silica content.  On one end is basalt, very low in silica but very high in magnesium and iron.  On the other is rhyolite, very high in silica and potassium that tends to erupt explosively.  In the case of obsidian, a cloud of rhyolitc ash hits the air, cools quickly, and literally shatters.  It has nothing to offer in terms of wine growing in a chemical sense, but it does have a huge effect on drainage.”

He continued by observing that “there is a full technical range of lava types in Lake County, very young chunks of rocks and glass weathered iron rich soil, which is why it’s red. What does it all mean for the vine?  It means generally high acid soils with low pH, making nutrient absorption very challenging.  In essence it is really a tough place for anything to grow.  Also, since the soils don’t retain much water, yields are quite low, and berries have a high skin-to-juice ratio.  The result is sturdy, well-structured wines with lots of acid and lots of tannin, very age-worthy stuff.”  

In other words, compelling wines may emanate from these young, rocky soils with low fertility.  Paradoxically, these soils are very rich in essential elements such as calcium carbonate, magnesium, copper and phosphorus.  These are essential elements for wine, but they are not available to the vines, because they haven’t been weathered into a form that the vine roots can absorb.  Given time, these soils can eventually become fertile.

According to the Lake County Winegrowers, High Valley is defined by steep mountain ridges rising up to 3,000 feet directly from this hanging valley’s floor at 1,700 feet.  Approximately nine miles long and three miles wide, this rare east-west transverse in the Californian coastal range was created by the volcanic activity of Round Mountain.  It is one of the very few east-west transverse valleys in northern California, circumscribed by a ring of mountains around a volcanic valley with a perfect center cone in the middle.  It gets plentiful sunlight, but only half the precipitation of other parts of the county.  It’s a demanding place to grow grapes but is it home to some of California’s best red wines.  High Valley in many ways is the most in intriguing volcanic region, still forming with a very rich and proud agricultural tradition in mid-Lake County.

Peter Molnar of Obsidian Vineyards said that he, Merrilees of Shannon Ridge and others have spent the past 34 plus years trying to understand this incredibly unique region. “The further we go, the less we know.  I think one of the things we have in mind when we farm here and vinify wines from our elevated, volcanic region is how different it is.  I have had the opportunity to travel to many wine regions in my cooperage work, and I must tell you that outside of Priorat in Spain, I think Lake County has the combination of elevation and soil to make it one of the most unique and exciting spots to grow grapes in the world right now.  While we are close to our Napa and Sonoma neighbors, I sometimes joke that we are further than you think, because of the combination of high elevation, luminous sunlight, very, very intense diurnal swings, and our incredibly young volcanic soils.  This ‘volcanization’ has been going on in Lake County for 15,000 years after populations started moving in.  It creates intensive mountain fruit, and mountain fruit is different from valley fruit in many ways.”

Molnar continued by noting that, “Lake County sits on top of a pool of magma which is coming up from the earth’s core and it’s hitting the bottom of our crust, the thinnest crust in North America, essentially boiling up from below.  It’s boiling with such energy that the geothermal field just south of our vineyards in the Red Hills region is powering Geysers Geothermal Complex, the biggest geothermal installation in the world.  It gives you a sense of the intensity of the forces active right now.”

The Red Hills start at 1500 feet and rise to 3,000 feet.  The soils throughout are very iron rich volcanic soil with a lot of obsidian throughout.  Over the course of the growing season, the grapes develop thicker skins, much more intense phenolics in the wine.  As the forests of Red Hills transition from the Chaparrals to the Pines and that combination of Live Oak and Pine really brings exciting herbal character to the wines.

There is a very rich agricultural tradition in mid-Lake County.  In the 1970s, Lake County wine grapes were planted around the lake.  Since that time, growers have moved up into the very young volcanic Red Hills or reddish hills that includes High Valley and Red Hills, both have a high iron content and very young soils. Molar said, Oour family started growing in Carneros in the early 70s.  We purchased our property in the 90s.  One of the stories I tell is that about 5 years into it we had our ‘Toto we’re not in Kansas’ moment.  Many of the techniques like canopy management, reduced irrigation, and cutting back on fruit, which you need in a fertile valley floor, are not going to work this elevation.  We are at almost 3,000 ft, among the highest vineyards in the North Coast.  We are on soils that are about 10,000 years-old and about 10,000 acres, so we don’t really have a lot of margins of error.”

“Our farming,” he continued, “takes a lot of attention. It’s an intensity of planning and intensity of farming.  You can’t get behind on maintaining and caring for your vines.  On the flip side, you get a lot of intensity.  So, the extra luminosity gives you tons of extra pigments in the grape skin, a lot of phenolics.  Your soils are so poor that you can never really grow high yields up here.  Also, we have the intensity of the diurnal swing from daytime highs and nighttime low, and those are critical in creating color and color intensity in the wine. So, it’s a bit of a rodeo sometimes. We’ve learned a lot the last 20 years, but in short, I think farming up here is really paying attention, learning to farm and understand a new region it’s part of the history of West Coast winemaking.”  Molnar believes their best wines are yet to be produced.

Asked by Jim Gordon how the marketplace values Red Hills or High Valley acreage and grapes compared with other parts of California. Molnar replied, “In short, I think that the highest goal that we have as growers and winemakers is to make wine that actually tastes like it came from a specific place. Personally, I don’t want to make the best wine in the world.  I would like to make the wine that you could only drink from Obsidian Ridge, for example.   Our wines, while they are structured and big can be quite light on their feet and have some real high tones and aromatics that people love in these wines.”

Joy Merrilees described how growing grapes in Lake County on volcanic soil is different from her experience making wines in Oregon and New Zealand and Western Australia. The well drained the soils have little nutrient value, so they focus on providing organic matter in the vineyard to help to help the grapes hold on to the water and nutrients they have.  While winemakers in other regions practice leaf removal to allow more sunlight on the grapes, she wants the leaves, because, she said, “we want those little umbrellas of shade.  We don’t want the grapes to desiccate in the really hot, dry sun and low water soil.”  Their main goals are increasing water retention and getting grapes to hang on and ripen as long as possible.  They have enough ripening days, enough growing degree days to get from bloom to ripeness. “We’re trying to achieve phenolic ripeness.  To do that we need hang time, and we need those leaves to lengthen hang time.”
Another challenge is tannins and how to tame them.  For Merrilees, “These are bold wines and have a lot of structure as previously mentioned, but it is due to the small berries.”  She described being in the and vineyard tasting grapes to decide when to pick, looking for phenolic ripeness.  “I’ll be out there in the vineyard tasting the fruit and chew up the skins and you can macerate the skins so much in your teeth that you try to taste the tannins to see if they are green or leaning more toward ripeness.  That is really the true test.  The brix (sugar content) might be there, the acid might be perfect, but if you’ve still got green tannins with heavy astringency in it, you’re not ready yet.  The grapes need to hang out a little longer until they are ready.”  They also work on tannin management in the winery, by pressing the grapes to get them off the skins early, removing the source of tannins. “We’ve also tried extended maceration, leaving the skins on the wine for a lot longer than the period where the wine has completed fermentation, which balances the fruit and the structure of the wine and soften the tannins. Those are the tools we have.  We haven’t found anything that’s a cure all yet, but we’re still experimenting.  We are still new to this.”  She notes that every vintage is different, posing new challenges on how to mitigate the tannins.  This can be particularly important if the winery has many of styles wines to make, with some intended for near-term sale, whereas other, more age-worthy wines are aged for 18 months or so before bottling.

In terms of how to describe these wines, Merilee thinks it’s difficult.  “There are very young volcanic soils in the Red Hills and slightly older volcanic soils in High Valley and the difference between the two regions is significant.  From the Red Hills comes richness with very fruit forward character and a decent amount of structure on the finish.  The High Valley there’s a little bit more soil retention and more organic matter, older soils with the same sort of dense character.  A common thread about volcanic wines is that they are intense, and the challenge is to find a balance of fruit and acidity.”

Molnar responded “I think how Joy described handling the material, the fruit, the intensity, etc., is different from other areas in the world where wine is made—and that is what makes this so much fun.  We haven’t quite figured it out. We’re proud of our wines, and we get some recognition, but we’re still in the stage of winemaking where we’re still turning the dial.  I think if it was easy, everyone would be doing it.  This is a uniquely beautiful place from a winemaking point of view and a visual point of view.  The wines are going to be unique, and I think our best work will be to make wines that people can see what Lake County can do.  This is what Lake County tastes like and we’re still working on that work right now.”        

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