On the Myth and Mystique of Terroir:
"Terroir" has meaning, but not the one claimed by many higher-priced wineries. There, it is more of a false marketing concept than anything else. The idea that minor differences in soil, light, wind, rain, and drainage (in short, your "terroir") make your grapes and wine fundamentally different from the grapes and wine made just across the road, is far more fancy than reality. My clay at Epona Vineyard in SW WA is sixty miles from the vineyards in the Willamette Valley, and yet it is pretty much the same clay that's at Ken Wright, or Beaux Freres, or at any other vineyard in the Willamette Valley. Sure, their clay may have more or less Manganese than mine, or mine might have more or less Magnesium, but the differences aren't enough to make our grapes taste significantly different from each other. And you can give names to the different clays in this area, such as Jory, or Willakenzie, but it's clay! And the fact that the Missoula Floods deposited some boulders from Canada ("erratics") throughout NW OR and SW WA, is very cool to study, but doesn't do much to differentiate vineyard soils in this area. The soil in SW WA is generally the same as the soil in NW OR--it's just that a giant river cuts through the middle of it, creating a boundary that we incorrectly assume means differences in the dirt on both sides.
There can be huge differences in the wines from vineyards that are adjacent or a few hundred yards away, but that is not due to terroir; it is due to different winemakers' skill levels and practices, and different harvest timing, and a thousand other such variables. You can call that "terroir" if you like. But it's not. If you listen to the higher-priced wineries, you would think their site is so special that you can hear angels singing there. Um, no.
And yet, it is true that the same grape will taste different across the world. if you want to see the differences that sites can make, in a grape, consider Sauvignon Blanc: In New Zealand it's got great (really great) lime notes, with a bit of a crushed oyster shell note. In France, it is minerality that drives, with more-subdued fruit notes. In the western US, it is less mineral and has stronger fruit notes, and it can be more grassy than lime-y. But those are gross regional differences. And they're not always present. Most wine lovers probably couldn't pick out which Cabernet Sauvignon or which Chardonnay was from Napa, or from South Africa, or from Chile.
So my advice is to think of "terroir" as a useful term, only when talking about the soil and sun and water IN A REGION, but don't fall victim to the marketing hocus-pocus that claims "our terroir is unique and better than our neighbors'." Just about everyone in these parts has good soil and great grapegrowing conditions. Yes, at a microscopic level there are differences in the terroir of each adjacent site, but the skill level of the winemaker, and a thousand other factors, are far more important than those tiny differences in terroir.
