Rising from the granite bedrock of the Gabilan Mountains east of Soledad, this fortress of towering spires and ramparts, now embedded in a 38sq mi national park, tells a complicated story of continental drift, ancient oceans and a vanished volcano.The park's distinctive ridgetop rock formations are the remnants of an unnamed volcano, formed 23 million years ago as the Pacific plate slid north past the North American plate along the fault now known as the San Andreas rift zone. This movement opened a deep crack through which molten lava erupted, forming an 8,000ft volcanic cone that straddled the fault itself. Over subsequent millennia, the Pacific plate continued its northward journey, carrying with it the western portion of the mountain; the remnants of the eastern half today lie some 195mi to the south.During this same period, erosion exposed the pinkish-gray ancient lava, known as rhyolite, beneath the surface. Tiny cracks in the lava's hardened surface were enlarged and deepened until all that remained were the striking stone towers that today punctuate the surrounding landscape of smooth, rounded hills.The park is accessible from both east and west. The west entrance provides access to a small ranger station and vantage points offering stunning views of the Pinnacles. The east entrance provides access to the Bear Gulch visitor center, which features exhibits on natural and cultural history. Both sections offer picnic areas and trails leading into the heart of the park.