Marine Terraces and Eroded Cliffs

November 05, 2009


Photographer: David Lynch; Dave's Web Page
Summary Author: David Lynch
Santa Monica, California sits on a wave-cut marine terrace that's been uplifted by tectonic activity to its present elevation of 80-100 ft (24-30 m). The underlying strata are composed of middle to late Pleistocene and Holocene alluvial fan deposits of consolidated silt, sand and gravel. Erosion and urban construction have produced impressive palisades. Their average inclination is about 77 degrees and they're continuously eroding, as shown by the debris fields just above Pacific Coast Highway at the lower left. Occasionally, part of a palisade will collapse, usually as a result of heavy rains that saturate and lubricate the soil. Such landslides can cover the highway, necessitating debris removal, weeks or months of road closures and in some cases the need to reroute the highway. Photo taken on August 14, 2009.