Serving professionals in engineering, environmental, and groundwater geology
since 1957

MONTHLY DINNER MEETING

Date: Tuesday, October 10, 2005
Location: Stevenís Steak House, 5332 Stevens Place, Commerce, California
Time: 6:00 p.m.-Social Hour; 7:00 p.m.-Dinner; 7:45 p.m.-Presentation

Cost: $30 per person with reservations, $35 at the door, $15 for students with a valid Student ID
Reservations: Call (323) 889-5366, or email Rosalind Munro,
By noon, Monday, October 10, 2005

PRESENTER: Dr. John Foster
TOPIC: Echo Landslide

ABSTRACT

The Monterey Formation crops out in the bluffs southeast of the Cristianitos Fault in San Onofre State Park, Southern California. The Park lies along the marine terrace bluffs between Interstate 5 and the Pacific Ocean and is an area of active landsliding. Echo Arch Landslide is clearly identifiable as two large concave alcoves that notch into the bluffs due southeast of the San Onofre Nuclear Generating Station which sits on unaffected long straight bluffs of terrace deposits covering San Mateo Sandstone. Movement is indicated by cracks and block falls that result from oceanward movement in a block glide. The geology of the landslide is light gray Monterey Shale (well weathered) capped by 20-30 meters of terrace deposits composed of thin marine gravel and sand with alluvial sand and minor gravel above. The landslide base is controlled by sheared soft weathered shale that is inclined oceanward at about 5 to 10 degrees but has an oceanward flattening bowl shape due to the geologic structure. The northwest boundary is controlled by the Cristianitos fault and the southeast boundary is structurally controlled by a northwest plunging anticline. In reality, however, the original landslide mass has long been consumed by the ocean and what remains and is still moving is a hummocky area of weathered Monterey Shale covered by headwall debris composed mostly of the terrace deposits. The headwall is slowly encroaching on the park road as topples and falls occur due to movement of the debris accumulating on the slide surface.

BIO

Dr. Foster is Professor of Engineering Geology at California State University Fullerton and is a registered professional geologist and engineering geologist in California. Dr. Foster has taught engineering geology for 16 years. His areas of expertise include the geology of landslides, active fault assessment and the geology of groundwater basins. He is currently working on a large contract with his colleague Dr. Richard Laton for the Mojave Water Agency to assess water flow, storage and capacity in natural rock basins of the Mojave Water Agency.