California's Weirdest Rocks: The Tufa

California can boast many superlatives: it contains the lowest point in the continental USA, the tallest, largest and oldest trees in the world, and it is the most populous state in the country. But to my mind, it also deserves the title of Home of the Weirdest Rocks, and it owes that honor to one rock in particular: the tufa. Essentially, it's a common rock -- limestone -- that forms in uncommon circumstances -- underwater. When calcium-rich underwater springs mix with lakewater rich in carbonates, a chemical reaction occurs which forms these impressive and bizarre-looking towers of limestone. Because they can only grow underwater, of course, the only places you can find tufa formations are places where there used to be a lake. California, as I've written about recently, is chock-full of those places, and two of them had just the right mix of calcium-rich springs and carbon-rich lakewater to form what have become nationally-recognized landmarks of geologic weirdness: Mono Lake and the Trona Pinnacles.

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