May 15th- OBHS presented “The Geology and Paleontology of Sunset Cliffs”

A large crowd attended the Thurs., May 15, 2025, The Ocean Beach Historical Society featured guest Dr. Tom Demere, who presented The Geology and Paleontology of Sunset Cliffs. at Water’s Edge Community Center, 1984 Sunset Cliffs Blvd., O.B. Tom Demere’s covered the Point Loma Peninsula’s general geologic history and fossils, with a special focus on Sunset Cliffs. Some 120,000 years ago, global sea level was approximately 20 feet higher than today, and the Point Loma landmass was an island (“Loma Island”) separated from the mainland by a combined “Mission Bay-San Diego Bay.” Tectonic forces, together with sea level fluctuation, resulted in uplift of the peninsula, leaving the ancient sea floor high and dry, with a relatively thin veneer of locally derived wind- and stream-deposited sediment that covered the old sea floor. The resulting, nearly level landform (uplifted marine terrace) makes an ideal place for the homes, businesses, roads, and alleys that characterize much of the communities of Ocean Beach and Sunset Cliffs. 
We learned about fascinating aspects of the local geologic history including how and when the resistant bedrock strata exposed in the sea cliffs formed, the time about 20,000 years ago when the global sea level was approximately 400 feet lower than today, the subsequent relatively rapid rise sea level, and the impact that sea level rise has and is having on the sea cliffs. All OBHS programs are FREE!