The main mountain ranges of the Peninsular Ranges ridging eastern San Diego–Tijuana are the Palomar Mountains, Laguna Mountains, Sierra de Juárez, and the peaks of the Cuyumacas including Cuyamaca Peak. The highest points are located in the Lagunas at 6,378 feet (1,944 m) and in the Cuyumacas at 6,512 feet (1,985 m) while the highest is the peak of Hot Springs Mountain at 6,535 feet (1,992 m). These mountain ranges constitute part of the Salinian Block, a largely granitic terrane dating back to the Mesozoic era and thus explaining the abundance of such stone throughout the region. Once part of the North American Plate, the Salinian block broke off due to the formation of the San Andreas Fault and rift resulting in the Gulf of California and its extension of the Salton Trough.