Glaciers’ Traces: How Glaciation Laid the Groundwork for Okanagan Valley’s Unparalleled Micro-Terroirs

September 7, 2016 - By 

Lying at the 50th parallel on the fringes of where grapes can ripen, Okanagan Valley may seem like an unlikely candidate for a major fine wine region. Yet the Valley is not only the largest producer of fine wine in British Columbia, but also one of the most prolific in Canada on the whole.

There are hundreds of wineries in Okanagan making wine from a wide variety of grapes. And it’s really good. But what makes this region so well-suited to wine production and why is it so unique? The answer lies with the forces which shaped Okanagan Valley, and to unearth the facts, we must go back in time.

Ice Floe, Nowhere to Go

If you’re looking for a single word answer as to why the terroir of Okanagan allows a breeding ground for such delicious wine it’s this: glaciers. During the last glacial period, the better part of Canada and the United States was smothered under various ice sheets. In an extremely simplified version of how the ice sheets were born, here’s what happened: heavy snowfall took place over years, layering, melting, and freezing until Cyclopean masses of ice formed. Once sufficiently huge the ice began to move under its own weight. Heat from the Earth’s surface would melt the bottom layer of ice, helping sheets to pick up some speed, spreading out until it eventually reached warmer temperatures and could go no further.  

The Cordilleran Ice Sheet formed over Alaska, British Columbia and the Pacific Northwest, advancing and retreating over the course of millennia. And so the land as we see it today began to take the shape. In the Okanagan glaciers carved away rocks, serving to both deepen and widen Okanagan Valley, all the while depositing sediment and other debris wrenched from the landscape as they moved. They sculpted the mountains and created countless lakes and depressions in the land which would one day become lakes, once the glaciers eventually melted.

Towards the end of the Pleistocene Epoch (the geological period that directly precedes the current Holocene Epoch), the ice sheets began melting causing a series of dramatic floods. The Missoula Floods, caused by the periodic melting of ice dams in glacial Lake Missoula, both devastated and helped define the landscapes  in Montana, Washington and Oregon are one famous example. Similar flooding happened in the Okanagan. Ice dams would block the drainage from the lake until either the ice dam melted or the water pressure became too great, causing calamitous flooding. This flooding, in addition to further eroding the Valley and stripping it of vegetation, also deposited sediment and other glacial drift in the many lakes of the region, notably Lake Penticton, the post-glacial precursor to Okanagan Lake.

Okanagan Lake

Okanagan Lake is the largest of the glacially-formed lakes that feature in Okanagan Valley. Surrounding the lake are fertile benches which today are the site of a variety of agriculture, in particular vineyards. These terraces are remainders of Lake Penticton, and all that glacial debris that was deposited during the flooding at the end of the Pleistocene, is the reason the land is so fertile.

But what does the itself lake have to do with viticulture? Okanagan Lake helps moderate the climate of the Valley. Reaching depths of up to 230 meters, it acts as a heat reserve, tempering cold snaps and one of the reasons why Okanagan Valley is prone to milder winters. Winemakers can rest a bit easier, knowing there is at least somewhat less of a risk of the devastating frosts that can decimate vineyards and drastically reduce harvests. At 160 km in length, Okanagan Lake provides its moderating influence to a whole slew of wineries. Other major lakes which help moderate the climate include Osoyoos Lake, Skaha Lake, and Vaseux Lake, but generally speaking there are serious amount of lakes in the Okanagan region.

So the glaciation sculpted the Valley. It carved out rock, and both the glaciers and repeated flooding deposited all manner of sediment and debris throughout the Okanagan region, resulting in a complex variety of soils micro-terroirs within the macroclimate of the Valley. The effect is most profound in today’s vineyards; a single plot of land can have upwards of five different soil types in the same block. The fact that a single vineyard can have such a composite soil makeup is one of the distinguishing facts of the Okanagan, and more than a few vintners have copped on.

Take for instance Intersection Winery. In recognition and celebration of the impact different soil types can have on a single varietal, the estate bottles two expressions of Merlot planted in sand, and rock and silt soils respectively. Alluvia, the version planted in rock and silt, is defined by its elegance and purity of fruit. This is in contrast with the Silica; the sandy soils help restrict the natural vigour of the Merlot grape and help yield wines of great concentration and an utterly silky texture. The vines are planted only a few meters apart from one another, and yet the wines they yield are utterly different.

Okanagan Crush Pad’s Switchback Vineyard is another prime example. The source of Haywire Winery, the plot was converted from a former orchard farm, and the winery team took the opportunity to identify specific micro-terroirs within the site to glean more insight as to how to best care for the vines planted within each.

Synchromesh’s vineyards dot the shoreline of Okanagan Lake from up by Kelowna down to the Golden Mile. They’re known for their premium single vineyard Rieslings and Pinot Noirs. Of all their vineyards, possibly the most geologically complex is the Storm Haven Vineyard in Okanagan Falls. Storm Haven is separated into five blocks, each of which is dedicated to either Riesling or Pinot Noir, depending on the underlying soil structure. At only 5 acres in size, the soil varies from clay and sand over gravel, to gravel and rotten granite with limestone bands, with each block comprising of a different soil ratio. The Storm Haven blocks planted to Riesling contribute layers of complexity in the final wine, achieving balance and maintaining acidity even in the hottest vintages.

The incredible diversity of Okanagan’s micro-terroirs is undoubtedly what sets the Valley apart from other winemaking regions worldwide. While famous regions like Bordeaux are largely characterized by only a few major soil types (namely gravel, limestone, and clay), the soil makeup of Okanagan Valley vineyards can change from one end of the plot to the other. It can even change from one row of vines to another. The complexity this imparts to the wines is what gives them an edge, and as producers continue to focus on highlighting the unique terroir expressions in their wines, it will lead the Valley forward as it continues to develop as a rising fine wine region on the world stage.

Camille Berry

Camille is a California born and bred writer and sommelier. Dedicated to the lifelong pursuit of wine knowledge, she can usually be found with her nose in a book or pouring over maps.
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