POINT REYES NATIONAL SEASHORE: A CREATION OF THE SAN ANDREAS FAULT AND COASTAL UPLIFT

The Point Reyes National Seashore is located about one hour north of San Francisco and is a popular destination for locals and tourists. The main attraction of this national park is the Point Reyes Peninsula, which is bounded on its eastern edge by the San Andreas fault (SAF), and along its other edges by the Pacific Ocean. The peninsula is part of the Salinian terrane, which has been transported at least 450 km northwest of its original location by motion along the SAF. During the Quaternary Period, the peninsula has been created by uplift and folding into a broad syncline. The western limb is a headland that juts far into the ocean and that is the best place to view whales without getting on a boat. The eastern limb is an extensive ridge with many well-used trails and backpacking camps. A landslide zone creates small lakes for swimming. The low-lying hinge area between the two fold limbs is an estero where oysters are farmed and kayakers paddle. The peninsula has many km of beach, ranging from northwest-facing beaches popular with surfers to south-facing beaches popular with families.

Two outdoor exhibits explain aspects of the peninsula’s geology. At the visitors center, an Earthquake Trail was created by Tim Hall in the 1970s. Although very basic and in need of updating, it is highly rated by the public because of its clarity and simplicity. At the western headland of the peninsula, signs explain an exquisite example of Paleocene submarine sediment-gravity-flow deposits. We plan to work with park personnel to create more exhibits about the park’s geologic origins. The most effective communications are clear images and a simple message. We hope to develop visualizations of the peninsula uplifting and slipping northwestward through time. Three-dimensional visualizations using digital elevation models and GIS software capture the attention of the general public.