(ChicagoTribune) - The entire reason for a wine's appellation, or the name of the place where the grapes are grown that make the wine, is to tell you what kind of wine it is.

The name may be significant because it is narrow and tells a lot; "Napa Valley" certainly is. It may be general, overarching and therefore difficult to parse; that's the case with "California." In both, and for all the appellations in between, the producer or winemaker often matters too. (There are many terrific wines simply labeled "California"; it just very much helps to know the reputation of those who made them.)

"Sonoma Coast" the appellation — statutorily called an American Viticultural Area or AVA — is 500,000 acres in size. Lots of wine comes from it, some good, some not so good, some great, some amazing. It's difficult to tell, however, from the appellation alone and without knowing much about the producer, what's up.

Half a million acres is three and a half times the size of Chicago; two and half times the entirety of the five boroughs of New York City.

Why so large? In 1987, when the federal government approved the AVA, the word "coast" had cache in the wine world, as it still does. It connoted cool-climate grape growing, long growing and ripening seasons, development of finely etched flavors and aromas in wine, lower alcohol levels and zippy acidity.

Those are characteristics that wine lovers seek in many a wine and are the opposite of what warm-climate appellations give to wine. In a political move worthy of the craftiest gerrymandering, some winemakers successfully lobbied the government to sweep into the AVA their far-flung vineyards within Sonoma County under the one AVA of Sonoma Coast.

The appellation now covers wines as disparate as those from Chalk Hill, a decidedly warm-climate sub-AVA, to those from close to Napa in the Carneros, to those from cool-climate Green Valley and those made along what's called, by winemaking rabble-rousers, "the true Sonoma Coast" (aka West Sonoma Coast), that is, from vineyards within view of the Pacific.

As winemaker Greg La Follette, who makes wine in the Sonoma Coast and other California AVAs, sums it up, "It is too large an AVA to be useful. … As it stands, there's no 'wine type' there, no definable system overall."

"Back in the day," says Greg Bjornstad, winemaker for Pfendler Vineyards and a vineyard consultant for many wineries within the Sonoma Coast AVA, "they said, 'Let's put everything in there.' At the time it was no big deal. But now the name is a draw, and it's always a challenge to talk about it."

I put together a tasting of wines, all of which carry the Sonoma Coast appellation. Some came from vineyards that hug the Pacific shores; some came from vineyards as far as 30 miles inland.

None of the wines was poorly made, but the differences between true coastal, or markedly cool-climate vineyards, and those from warmer regions within the AVA was striking.

Someone once told me that if you want to smell the difference between wines from Europe and those from the Americas, sniff out the aromas of earth or minerals in the former and the lack of them in the latter. Also, note the higher levels of acidity in the former and the lower levels in the latter.

Those differences, goes the suggestion, are due to the generally differing climates in grape-growing regions between Europe and the Americas. (This is, of course, a huge generalization.)

From the Sonoma Coast, the scents of minerals or earth, and definitely lower alcohols and finely etched acidity, quite comes to the fore in wines, both white and red, made from grapes grown closer to the Pacific.