Geologic Field Trips in and around Highly Developed Areas in Los Angeles, California

Southern California is a geologist's delight when it comes to introducing students to basic geologic processes in the field. One does not need to travel far to find evidence of faulting, folding, and mountain building, coastal deposition and erosion, and features associated with depositional and hydrologic systems. While geologic field trips typically take students out of urban areas and into natural settings, there are many features in the heart of developed urban Los Angeles that can be worthwhile to examine. Much of the metropolitan region was built before the practice of grading the land was common, thus many geomorphic features remain identifiable beneath asphalt and public lands. These types of trips can make great impressions on students because many do not realize that they are living so close to river channels, landslides, marine terraces, alluvial fans, tar pits, or active faults. In particular, visible fault scarps in highly urbanized areas include the Raymond, Hollywood, Santa Monica, Newport-Inglewood, Sierra Madre, and Palos Verdes faults. Many streets, such as Beverly Glen, Santa Monica Boulevard, and the Pasadena Freeway, were built in old stream channels. The concrete-lined hydrologic system in Los Angeles includes the 51-mile-long L.A. River and the many tributaries and dams that are part of that system, including Arroyo Seco, Devil's Gate, Eaton Canyon, and St. Francis Dams, and lakes caused by dammed drainages such as Silver and Echo Park Lakes. Alluvial fans underlie the gentle slopes of cities located at the base of young mountains such as Altadena and Hollywood. An oxbow lake at Harbor Park on the Palos Verdes peninsula formed when the earlier Los Angeles River passed this way. The peninsula is also home to at least thirteen late Pleistocene wave-cut terraces that were uplifted in the past three million years.