Close to Home presents a talk and slide show...

History of San Francisco Bay

The Current One Is 10,000 Years Old and Leaving Soon

with Ken Lajoie (USGS)

Monday, May 4, 2009      7:30 P.M.

Montclair Presbyterian Church in Oakland

Just 10,000 years ago, near the end of the last ice age, sea level was about 350 feet lower than it is today and there was no bay. The beach lay out beyond the Farrallon Islands , about 25 miles west of San Francisco.

As continental glaciers melted, the broad, low area in the Coast Ranges of Central California filled with water to form the bay. It only reached its present size in the last 2,000 years. Geologic data from deep borings beneath the south bay indicate there were at least five previous bays, each occurring during brief interglacial sea-level high stands at about one-hundred-thousand-year intervals. Within the next few thousand years the climate will begin to cool at the onset of the next ice age, and the continental glaciers will again expand, causing sea-level to fall and the present bay to drain away. At the end of the coming ice age, in about one-hundred-thousand years, sea level will again rise and form the next San Francisco bay. 

The oldest archeological sites in the bay basin are about 5,000 years old, but it’s quite likely that early peoples occupied Central California at least 15,000 years ago – before the current bay existed. Ken will treat us to the big picture of our natural bay history with stories and a slide show.

Ken Lajoie is a geologist, retired from 30 years of service to the U. S. Geological Survey. He’s also an expert on episodic natural events.

Hosted by: Close to Home: Exploring Nature in the East Bay            

Co-sponsors:               

• Ecostewards of Montclair Presbyterian Church
• Oakland Museum of  CA   /   Bay Nature magazine
• Lindsay Wildlife Museum  /   EarthLight community

Donation: $5  (K-12 Free)

Montclair Presbyterian Church is located at 5701Thornhill Rd. in the Montclair area of Oakland. Take the Thornhill exit on Highway 13 and go east ½ mile. Parking available in lot ½ block west and on street. For more information: Cindy Spring (510) 655-6658  www.close-to-home.org

On June 8 Marilyn Lattaof the Coastal Conservancy will bring us up to date on East Bay wetlands restoration and efforts to bring back oyster and bird habitats.