San Francisco: Where the Plates Meet

Typical rocks of the Franciscan Complex in mélange zone where Marin Headlands terrane come onshore at Baker Beach, San Francisco. These are ancient pieces of seafloor that were added to the North American plate margin rather than subducted beneath it.

William Elder

January 2021 - The San Francisco Bay Area sports “coasts with abundant marine and terrestrial resources, a sheltered deep-water harbor, hills and mountains with plentiful forests, and streams and rivers providing water and transportation routes, including to the goldfields of the Sierra Nevada Mountains.” As a result, it has attracted people to it for millennia. But why does the area feature such enchanting diversity in the first place?

The answer lies with the region’s geology and tectonic activity starting some 200 million years ago. Join Golden Gate National Recreation Area Geologist Will Elder on his recent post for the European Geosciences Union’s Tectonics and Structural Geology (TS) Division blog to discover the geological stories that lie beneath the Bay Area as we know it.

For more information

• Tectonics and Structural Geology Blog: San Francisco: Where the Plates Meet
• Golden Gate National Recreation Area: Geologic Activity
• Contact Golden Gate Geologist and Visual Information Specialist Will Elder

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