Hydraulic fracturing — or fracking for short — has become a hot topic in California as the oil industry seeks to tap into a rich underground reserve of oil in the Monterey Shale formation, which stretches from Southern California to the Bay Area’s doorstep in Monterey County. In a Bay Nature magazine-web series, we explore what we stand to lose if California embarks on a new oil boom and the geology behind what’s said to be the largest reserve of oil in the U.S.