The U.S. Geological Survey has mapped artificial land along with all the other geologic units around the Bay. The majority of this reclaimed land is in the central Bay, in San Francisco and Oakland.

Reclaimed land shows its weakness in earthquakes. In the 1906 quake it was widely noted that buildings placed on "made land" were prone to failure. Nonetheless the city's rubble was used for fill at the site of the 1915 Pan Pacific Exposition, which later became developed as the Marina district. In the 1989 Loma Prieta quake the Marina had the deadliest damage in the city. Likewise, the Cypress section of Interstate 880, in west Oakland, failed where it crossed old fill. In San Francisco the notorious Embarcadero Freeway, also built upon old fill, was torn down shortly after Loma Prieta, before it could fail. Our areas of fill, old and new, will continue to be tested by earthquakes while our reclamation practices continue to improve.

For geology enthusiasts, Oakland's reclaimed land has given us an unexpected treat, seen in the new Middle Harbor Park.

madelandtop — A replica seawall recycles rock from an early land reclamation project: the port of Oakland. Photo by Andrew Alden.

In the 1880s, early in the creation of Oakland's harbor, a pair of "training walls" was built to guide the tides into scouring the ship channel clean. The project required lots of large boulders, and every quarry along the Bay Area shoreline was recruited to supply the stones. When the old north training wall was demolished in 2001, some of the best rocks were set aside. These were made into a replica pier, nicely laid down in drystone masonry, that displays excellent specimens of Bay Area rock types.

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