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Out of the Pangaean Mists a River Is Born
When I set out to write this book, I decided that a part of it had to be devoted to an account of how the Russian River was born.
It proved to be no easy task. I searched for some account that would describe the geologic processes that led up to the great moment (or so I imagined it) when the first few droplets of water gathered into a trickle, the trickle into a brook, the brook into a mighty stream....
But there was no such book. So instead I set out in search of scientists who could help me understand not only the river's genesis but also why it takes its weird turn west. As it turns out, however, little agreement exists among geologists, except in an overall sense, about the Russian River's origins and behavior. Even long-cherished theories about Northern California's plate tectonics, forces central to the region's formation, are rapidly being revised and debated.
When I asked winemakers to suggest a geologist to consult, the first name to surface was that of Terry Wright, a geology professor, since retired, at Sonoma State University in Santa Rosa. "He's the man," people said. "Nobody's done more to understand Sonoma's geology and its effect on wine than Terry Wright."
His full name, I discovered, was William H. Wright; he had a geology Web site. I emailed him to request a meeting. The reply came back promptly.
"You can interview me," it read, "if you buy me lunch."
The professor chose Sassafras, one of the most expensive restaurants in Santa Rosa. I drove up from Oakland and, on a sunny autumn day in 2002, made the acquaintance of this boisterous, friendly, and larger-than-life academic.
I recognized him the moment he walked in from the parking lot. He looked like an aging Indiana Jones, from the rumpled khakis to the big brown safari hat. His face sprouted a full, bushy white beard and a flaring walrus mustache. Terry Wright is a great bear of a man, somewhere in his sixties, tall and well fed, a rock hound who can identify any pebble you show him. Moreover, he possesses a passion for fine wine.
Later, when I got to know Terry better and visited his house, I was hardly surprised, for it seemed well suited to such a character—a funky, ramshackle hobbit's hut spilling down the side of a mountain in Forestville, on a tortuously crooked road, deep in a conifer forest above the Russian River. In the front yard lay piles of stones, brought home from his excursions. In the house, every shelf and level surface was covered with rocks, fossils, lava, little plastic Baggies filled with dirt. It was as if he had brought the earth inside.
Over lunch (three glasses of red wine for him, none for me),Terry described, in increasingly rapturous tones, his adventures rock climbing, his whitewater rafting trips on the Colorado River through the Grand Canyon, his nights of carousing and partying and living always on the edge, sometimes risking his very life for excitement. I began to feel that I had lived a very safe and timorous existence, I told him, and to wonder whether I had missed out on some elemental, manly rite of passage. "Maybe you'll find out someday," Terry replied.
He was a swashbuckler and a charmer.
I also got to know Daniel Roberts, then director of winegrowing research at Jackson Family Farms, an upscale branch of the empire created by Jess Jackson, of Kendall-Jackson. Roberts is as famous as Wright among winemakers and grape growers. Julie Martinelli, whose family owns the well-known Russian River Valley winery that bears their name, calls him "Dr. Dirt." He is the Apollonian opposite of Terry Wright's Dionysian sensuality: intellectual and precise, well-organized to a fault, orderly in his habits, a man who does not suffer fools gladly. Roberts is a sort of Colonel Pickering to Wright's Henry Higgins.
I soon realized that there was little love lost between Drs. Wright and Roberts. But then, Wright studies geology—the deep-down structure of rocks—and Roberts focuses strictly on surface soils. And plenty of tension exists between these two sciences when it comes to viticulture.
Their rivalry (if that's the word) underscores the deep ambiguity that surrounds the topic of the influence of rocks and soil on grapevines and wine—a topic generally referred to by a word I will use only sparingly in this book: terroir. Although much is made of the nuances of silt over clay, or clay over silt, or sand over pebbles, or hardpan below clay, or limestone soils and volcanic soils, et cetera ad infinitum, the truth is that no one fully understands the precise mechanisms by which soil and rocks influence viticulture and wine; indeed, it may be impossible to understand and calculate such impact, especially when the geology is as complex as Sonoma's. Then, too, much depends on the talent of the viticulturalist, who can undermine a potentially great piece of land so that it produces only mediocre grapes.
The third scientist to whom I turned was Dr. Deborah Elliott-Fisk, a professor in the Department of Wildlife, Fish, and Conservation Biology at the University of California at Davis. You'd never guess it from her title, but Elliott-Fisk has developed something of a cottage industry analyzing the geology of wine country in Napa and Sonoma counties. Like Wright and Roberts, she consults for wineries. Her theory about the Russian River, described in chapter 5, turns out to be a real stunner—although it is rather at odds with the current understanding of Northern California's geology.
All three of these scientists offered patience, knowledge, and additional resources. But none of them could tell me the complete story of how and when the Russian River began. For that, I had to create my own account. Thus, caveat lector, for I am not an expert in this field. I absolve the three good scientists of responsibility for any errors that may appear and give them credit for all that is correct in my account.
* * *
It is not necessary to recapitulate here the history of Pangaea—"all lands" in Greek—the last (but not the first) great supercontinent, on whose vestiges all land life currently resides. Suffice it to say that Pangaea arose from the watery depths toward the end of the Paleozoic era, about 250 million years ago. By the time of the Cretaceous period, about 110 million years ago, it was already splitting apart, in the never-ending process of continent formation, destruction, and recycling.
Eastern North America was part of Pangaea. But 100 million years ago, the California coastline was located about where the present-day foothills of the Sierra Nevada lie. Everything to the west, including modern Sonoma, was underwater, part of the ancient sea floor.
Most of the county's foundation is built of bedrock that was formed beneath that sea between 150 million and 40 million years ago. Yet there are remnants of rocks in Sonoma whose paleomagnetic properties suggest that they are far more ancient. They exist in isolated outcroppings of granite that can be seen at Bodega Head, on the coast near Bodega Bay, and are as exogamous to Sonoma as that monolith in 2001: A Space Odyssey was to the moon. These rocks are identical to granites found far to the south, in the Big Sur, Santa Lucia, and Gavilan ranges of Monterey County; in the Tehachapi Mountains of Southern California; and even in Baja California. This suggests that, once upon a time, rocks now separated by hundreds of miles were in physical proximity.
Understanding how those southern rocks got up to Bodega Head is the key to understanding Sonoma's geology, and it involves the theories of plate tectonics and continental drift. For hundreds of millions of years, across the world, undersea volcanoes have belched forth molten igneous material that hardens on exposure to cold water, forming sea floor, which then congeals into large formations called plates. Plates are separated by fault lines, which are where earthquakes happen, as the gigantic slabs of land crunch and grind against each other.
Sonar, which was developed during World War II and originally used to locate German submarines, has subsequently been employed by scientists eager to map the ocean floor, an area even less well understood than parts of outer space. They discovered undersea mountain ranges separated by valleys riven with fissures. Geologists attempting to explain this pattern theorized that the sea floor was spreading very slowly away from the fissures as lava oozed out from them, driven by fierce convection currents in the earth's molten mantle—a conjecture now supported by evidence from underwater photography.
The earth's mantle is a deep well of hot liquid and semiliquid rock, or magma, located many miles below the hard outer crust. It is heated to the melting point by the decay of radioactive elements such as uranium and thorium and by residual heat that remains from the planet's fiery creation. Off the California coast, the lava-oozing fissures run in a more or less north-south orientation. As the magma spilled out and spread, the new ocean floor pushed relentlessly to the east and west, like a part in thick, wavy hair, until it came into contact with something that impeded it.
Where the sea floor flowed east, it met the ultimate obstacle: the gigantic wedge of the North American continent, which itself was lurching westward, the result of the continuing breakup of Pangaea. Finding its way blocked, the eastward-flowing sea floor had only three options: it could switch direction and flow north or south; it could rise up and over the continent, swamping it; or it could dive down below the continent, in a process geologists call subduction.
The new ocean floor—let us now call it by its proper name, the Farallon plate—dove down below the North American plate, in a subductive motion. When it was entirely subsumed beneath the North American plate, the Farallon disappeared from geologic history. The plate that replaced it—created by the same undersea forces that had created the Farallon plate—now began to grind sideways against the North American plate, rather than subducting beneath it. Geologists call this new slab of bedrock the Pacific plate.
* * *
The Coast Ranges are the mountains that run for 550 miles along the California coast, in parallel ridges located close to the ocean and about thirty miles inland. Geologists further differentiate the Southern Coast Ranges and the Northern Coast Ranges, with the dividing point at San Francisco Bay. Although they are considered part of a single great mountain chain that also includes the Klamath and Siskiyou mountains and the Sierra Nevada, the two Coast Ranges are built of different rock.
The northern mountains are composed of a type of bedrock geologists refer to as the Franciscan Complex, or Franciscan Formation. Formations are mappable, large-scale rock units that possess common characteristics, such as origin, age, or physical and chemical composition. They are usually named after a locality; the Franciscan honors San Francisco. Many of the big rock outcrops you see in San Francisco and Marin counties, such as the soaring cliffs on the northwest side of the Golden Gate Bridge, are made of Franciscan material. They are the visible parts of the western continent's undergirdings. All of Sonoma County east of the San Andreas fault and most of it west of the fault—which is to say about 98 percent of the county—is built of Franciscan rock.
The Southern Coast Ranges, by contrast, are built of Salinian rock, named after the city of Salinas, a hundred miles south of San Francisco. And that brings us back to those outcroppings at Bodega Head. They are made of Salinian rock. How did they find their way into Northern California?
The Farallon plate was subducted beneath the North American plate for tens of millions of years, until a milestone date in coastal California's geologic march through time. That milestone occurred about 29 million years ago. Mention that time frame to any geologist in California, and you'll see a flash of recognition.
At that time, the Farallon plate had been entirely subducted beneath the North American plate; subduction along the Central California coast had come to an end. Following the Farallon, the Pacific plate began (for reasons no one has ever successfully explained) to grind against the North American plate, the former inching slowly toward the northwest, the latter inching equally slowly toward the southeast. In geologic parlance, the two plates were in strike-slip, or horizontal fault, motion relative to each other. It was this strike-slip creeping that brought those old Salinian granites up from the south to Bodega Head. Like the latch on a zipper, they hitchhiked a slow ride north, at the rate of a couple of inches a year, on the migrating Pacific plate. With the arrival of strike-slip, this new line separating the two plates became the San Andreas fault.
The formation of the Coast Ranges resulted, initially, from subduction. Under a subduction regime, the top plate is thrust upward; the bottom plate becomes the recycled material for more land-building. Terry Wright, in a homely metaphor, refers to this subductive crunching of land as "mooshing two piles of Cheerios together."
When strike-slip took over, according to past theory, the Coast Ranges continued to rise ever higher, as earthquakes buckled the land—much as the 1989 Loma Prieta earthquake raised the height of that peak by a few inches. This is true, as far as it goes, but this strictly mechanical model fails to take full account of the heat of the Earth's magma.
A new theory arose in the 1990s, based on what was called the Mendocino Triple Junction model. It argued that the Southern Coast Ranges had indeed been built by subduction and, later, by strike-slip horizontal motion caused by earthquakes. But the Northern Coast Ranges were more problematic and more complicated. To understand them, we must take into account the Gorda plate.
The Gorda runs off the Pacific Northwest; it is being subducted beneath the North American plate, just as the Farallon plate was, in what is known as the Cascadia subduction zone. That subduction is responsible for creating the Cascade Mountains and may someday also cause the huge earthquake geologists are concerned may wreak havoc on Seattle.
The Pacific, North American, and Gorda plates currently come together off the Mendocino coast, at the so-called Mendocino Triple Junction. The junction has been migrating northward since it formed (it was south of San Francisco 16 million years ago, and off the coast of Sonoma County 10 million years ago).Where the three plates intersect, their edges don't fit perfectly together; imagine three irregularly shaped pieces of slate, with various gaps. Through this slab window, the mantle's hot magma wells up. At some 2,000 degrees Fahrenheit, the magma blisters the crust, just as a flame blisters the varnish on a table. Writ on a large scale, the "blisters" are mountains; as the slab window drifted from south to north, so did the blisters we call the Northern Coast Ranges.
It took a Pennsylvania State University scientist, Dr. Kevin Furlong, and his colleagues to refine the Mendocino Triple Junction theory into the current model. They were alerted by troubling findings uncovered by other geologists who studied how earthquake waves are propagated in Northern California. These geologists discovered that the crust is substantially thicker at the Mendocino Triple Junction, where it averages thirty miles in depth, compared to only about twelve miles thick north and south of it. This disconcerting fact discouraged the slab window theory of mountain building, because a thirty-mile-thick wedge of crust would effectively insulate the "varnish" from the underlying heat, like asbestos wrapped around a hot water heater. A new twist was needed to explain the Northern Coast Ranges.
Furlong's theory, still controversial, is called the Mendocino Crustal Conveyor, or MCC, model. According to MCC, as magma welled up through the slab window at the Mendocino Triple Junction, it cooled a became viscous, forming a sticky glue that welded the bottom edges of the Pacific, Gorda, and North American plates together. This did not prevent strike-slip from occurring, however. As the northwest-trending Pacific plate continued to grind against the southeast-flowing North American plate, to whose western edge it was now partially "glued," the Pacific plate dragged the North American plate along with it, creating enormous geophysical stress and forcing the North American plate to buckle and substantially thicken near the Mendocino Triple Junction but to thin out south of it. In the wake of the Mendocino Triple Junction's northerly migration, this pattern of thicker and thinner crust has resulted in two great mountain building "humps" that continually are conveyed northward along the San Andreas fault; hence the use of the term "conveyor." The recycled material for the thickening comes from south of the Mendocino Triple Junction, where the crust had earlier been thickened. The result has been the steady uplifting and lengthening of the Northern Coast Ranges.
Excerpted from A Wine Journey along the Russian River by Steve Heimoff. Copyright © 2005 Steve Heimoff. Excerpted by permission of UNIVERSITY OF CALIFORNIA PRESS.
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|1||Out of the Pangaean mists a river is born||9|
|2||Cyrus Alexander finds a valley||27|
|3||Alexander Valley Cabernet Sauvignon||51|
|4||Mountain Cabernet Sauvignon||74|
|5||Healdsburg : the crucial turn west||112|
|6||The Russian River Valley||129|
|7||Pinot Noir comes to Westside Road||161|
|8||Clones, AVAs, and storms : a divertissement||196|
|9||Into the fog, and above it : the Sonoma Coast||222|
|Recommended wines and producers||253|