Geology

Terroir 101

Christophe’s excitement over the field of stones he discovered in 1996 was for good reason. He had seen similar terroir in the Marlborough region of New Zealand, and in the “galets roulés” [rolled stone] vineyards in southern France. The area has even been dubbed “Oregon’s Châteauneuf-du-Pape,” home to some of the finest grapes grown in the northwestern United States. Christophe believes great wines must deliver a mineral quality—something his stony ground offers in abundance. And as he says, "The proof is in the wine."

Experts on the terroir of Cayuse vineyards describe vine roots snaking through an accumulation of cobblestones of varying sizes, a layer hundreds of feet thick in places. This soil, called “Freewater very cobbly loam,” sits atop 10,000 feet or more of pure basalt—a 15-million-year-old bedrock stratum that’s a part of one of the largest areas of basalt lava on the surface of the earth, outside the ocean basins.

“Wherever you go, there is something great terroir has in common—poor soils,” Christophe explains. Because the stony soil offers excellent drainage and limited nutrients, the vines have to struggle to produce their precious fruit. High density planting forces their root systems to compete and dig deeper for moisture and sustenance, and the heat transmitted by the stones helps the grapes to ripen.

The Missoula Floods

The creation of Christophe’s vineyard terroir can be traced back to the Missoula Floods, a series of geologic cataclysms that swept across Eastern Washington and down the Columbia Gorge at the end of the last ice age, between 12,000 and 15,000 years ago.

The massive floods, caused by periodic ruptures in the ice dam that created Montana’s Glacial Lake Missoula, inundated the Walla Walla Valley at least 35 times, experts say. At its highest point, the water elevation was about 1,200 feet—or the equivalent of 150 feet higher than the top of Walla Walla’s tallest building, the 12–story Marcus Whitman Hotel.

Each time those waters receded and the Walla Walla River rushed back into the Valley, the layers of sand and silt deposited by the floods were swept away and replaced with basalt pebbles, cobbles, and boulders washed downstream from the nearby Blue Mountains. These gravels accumulated over time, creating a 12-square mile alluvial fan of 3,770 acres where the river exits the Blue Mountains.

The chemistry of the alluvial fan soils that host the Cayuse vines is quite different than that of most other soils of the Walla Walla AVA. While sediments throughout much of the appellation are derived from Missoula Flood sediments that are rich in granite-derived silica, sodium, and potassium, Cayuse vineyard sediments are derived from Blue Mountains basalt, and loaded with iron, magnesium and calcium.

It’s a difference Christophe believes can be tasted in the wine, revealing the unique character and tempestuous history of the land itself. “Minerality is what makes the fruit intriguing and distinctive,” he says. And thanks to the power struggle between the Missoula Floods and the Walla Walla River, there’s plenty of excitement in every glass of Cayuse.