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Going Coastal—The Geology of California Cool

By Karen MacNeil
August 31, 2017

When a lot of people think about California, they think about bikinis. But when those of us who live here in wine country think about it, we think about down jackets. There are more than 700 miles of cold coastline stretching the length of the entire state. The effect of that coast on California wine is nothing short of profound.

While it’s tempting to think of California’s coasts as static, they are actually  quite dynamic geologically—which is to say they are in the process of being formed right this minute. I’ll explain how momentarily. But first, a word on how California gets its cool (thermally speaking).

The process works like this: California’s coast is pummeled by cold ocean currents spilling south from Alaska. For as cold as they are, those currents also produce coastal up-welling, raising even colder water from the depths of the Pacific Ocean. Blowing across this mass of cold water, fierce onshore winds grow colder themselves. And these of course have a chilling effect on vineyards that are closest to the coasts.

But even valleys farther inland feel the frigid effects. That’s thanks to the state’s enormous Central Valley (where a lion’s share of many U.S. fruits and vegetables are grown). As the Central Valley heats up, the mountainous terrain ringing it concentrates the solar radiation. Inevitably, the hot air rises, and in the vacuum that’s created, cold marine air is sucked in over and through every gap in the coastal mountain ranges.