These are the sites for the field trip to the still moving landslide at Portuguese Bend located within a much larger Pliestocene landslide. Stop 1 is an overlook from Del Cerro Park of the landslide. Del Cerro Park is located on the crown of the ancient landslide and is located just north of the major head scarp of this landslied. Most of the ancient Pleistocene landslide complex is visible from the Park, along with the twentieth century Abalone Cove (Stop 2) and Portuguese Bend (Stops 3 and 4) landslides.
Below is a view from Stop 1 of the ancient landslide and the very recent Portuguese Bend landslide. A fault scarp can be seen above the dirt road cutting through the center of the slide. This is stop 3. This scarp marks the eastern border of the recent landslide. In the 50's many houses were built in the area. All were destroyed by the motion of the landslide.
Stop 2. Abalone Cove. A photograph of the eastern side of Altamira Canyon which runs up the center of the landslide. The sedimentary features show that portions of the Abalone Cove have moved as coherent blocks maintaining its original bedding features.
Stop 2 Abalone Cove. A detailed shot of the wall of Altamira Canyon showing that during the landslide portions of the coherent sedimentary sequences have been thrust and crumpled over each other.
Stop 3 Portuguese Bend landslide. A scarp created by horizontal motion and down drop faulting along the eastern border as the landslide has moved five to six hundred feet towards the south (right hand side of the picture).
Between stops 3 and 4. Portuguese landslide. The Abalone Cove slide was stabilized by pumping out water from the sediments. Similar efforts were made to try to stabilize the Portuguese Bend landslide but they were much less successful. Below is piping for transporting the pumped out water from this landslide under Palos Verdes Drive to the ocean.
Palos Verdes Drive between stops 3 and 4. The still moving Portuguese bend landslide is cracking apart the asphalt of Palos Verdes Drive. The road has to be resurfaced on a yearly basis to cover up the cracks created by hte still moving landslide.
Close to stop 4 on the western end of the Portuguese Bend landslide. The house is south of Palos Verdes Drive and just on the western edge of the landslide. It is moving slowly towards the sea and ultimate destruction. Power and water lines follow it down the slope.
Stop 4 Basaltic dyke and hard sedimenary beds at Inspiration Point at the western edge of Portuguese Bend landslide. The dyke and the hard sedimentary beds do not erode and the sediments of the landslide pile up against them.
Stop 4. View along the beach at the toe of the Portuguese Bend Landslide. Motion of the landslide occurs along the top or within the top of a bentonite shale called the Portuguese Tuff. This tuff when saturated loses strength and allows the flow of the material above it. Beach erosion at the toe of the slide is removing the support that would normally stabilize the landslide, helping to keep it active. The rocks along the beach but up against the upper portions of the bentonite shale layer. The top of the shale layer is marked by an almost vertical slope at the bottom of the cliff.
