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Feb 28, 2015 · The geology you see around San Francisco is the result of forces along the Pacific and North American plates. Today, the Pacific Plate is slowly creeping north past the North American Plate, forming the San Andreas fault system. San Francisco Bay was created by movement on these faults about 650,000 years ago.

Although the valley in which San Francisco Bay resides probably began to form 2 to 3 million years ago, when the surrounding mountains and hills started to rise on either side, the first known estuarine (marine influenced) rocks were laid down only about 600,000 years ago, as dated by the Rockland ash bed which overlies the earliest marine rocks (Sarna-Wojcicki; pers. comm., 2001).

San Francisco Bay, large, nearly landlocked bay indenting western California, U.S. It is a drowned river valley paralleling the coastline and is connected with the Pacific Ocean by a strait called the Golden Gate, which is spanned by the Golden Gate Bridge. San Francisco Bay is 60 miles (97 km)

The sand at Ocean Beach and in the sand dunes of northern San Francisco is really a relic, a gift from the past. These sands were deposited along the western shoreline of the San Francisco peninsula during the Wisconsin glacial period, from 10,000 to 15,000 years ago, when sea level was low and the Sacramento River flowed through the Golden Gate.

May 21, 2015 · The new “Offshore of San Francisco” maps document the complex submarine environments along the inlet to San Francisco Bay formed by strong tidal currents, including spectacular sand waves, a deep scour pool beneath the Golden Gate, and the dynamic offshore San Francisco mouth bar and “Potato Patch” shoal. Sediment distribution maps reveal only a thin sediment cover offshore of the Ocean Beach (San Francisco) erosional hotspot (a pattern extending south to San Gregorio), indicating ...

The Delta was formed by the raising of sea level following glaciation, leading to the accumulation of Sacramento and San Joaquin River sediments behind the Carquinez Strait, the sole outlet from the Central Valley to the San Pablo and San Francisco Bays and the Pacific Ocean. The narrowness of the Carquinez Strait coupled with tidal action has caused the sediment to pile up, forming expansive islands. Geologically, the Delta has existed for about 10,000 years, since the end of the Last Glacial P