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Geologic Trips, San
Francisco Golden Gate San Francisco is built on a thick suite of
unusual red, green, gray, black, blue, yellow, and brown rocks called the Franciscan. These rocks were formed in the Franciscan subduction zone as a result of a slow-motion collision between two of
the large plates that covered the surface of the earth during Cretaceous
time. San Francisco is one of the best place in the world to observe the
innards of a subduction zone. The fraternity of rocks once housed in the
subduction zone are well exposed and have been investigated by geologists and
other scientists for over a hundred years. As a result of these studies we
know where the rocks came from, how and when they got into the subduction
zone, and what happened to them during the subduction process. It’s a
fascinating story. And the story is written in the hills and sea cliffs of
San Francisco and the Marin Headlands. Exterior Websites Golden Gate NP Conservancy: US Geological Survey:
Geology
of San Francisco Bay Area Wikipedia: _____ |
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The Golden Gate Bridge from the Marin
Headlands. |