For a big state, California’s oyster industry is confined to a small area. Tomales Bay is the center of the action, with several small growers, including Hog Island. Coast Seafoods, the largest oyster company in the country, has major Kumamoto farms to the north in Humboldt Bay. Other than a handful of quixotic operations in Carlsbad, Santa Barbara, Morro Bay, and Drake’s Estero, that’s it. It’s all in the geography. California isn’t blessed with many bays. It has one world-class bay (San Francisco), and one dinky one (Humboldt). San Francisco Bay held billions of Olympia oysters in the 1850s, zero in the 1860s. By the time Pacific oyster seed was available from Japan, San Francisco Bay was far too polluted to grow oysters. Tomales Bay, the other workable water body, is a geological freak. When Point Reyes, the tomahawk-shaped wedge of land that is the tip of the Pacific Continental Plate, slammed into the rest of California, which edges the North American Continental Plate, it didn’t make a perfect fit. Tomales Bay is the imperfection, more a crevice than a typical bay. That imperfection is sliding northward at a rate of two inches per year as the plates continue to grind together. Every now and then they come unstuck and jump—twenty feet at once in 1906, leveling much of San Francisco in the process. In geological terms, Tomales Bay is living on borrowed time.