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Geologic Trips, San
Francisco Alcatraz Island Alcatraz Island is one of the best places in the Bay Area to see the
Alcatraz terrane of the Franciscan. The Alcatraz terrane is characterized by
thick-bedded sandstones. These sandstones form many of the hills that give
downtown San Francisco its unique character, including Telegraph Hill, Russian
Hill, Rincon Hill and Nob Hill. However, in San Francisco, the Alcatraz
sandstone is almost everywhere covered by buildings, streets and cable car
tracks, so that good exposures are hard to find. The
steep cliffs on the southwest shore of Alcatraz Island, seen in this photograph, are formed from thick beds of the
Alcatraz sandstone. There are also good
exposures of the sandstone along many of the paths on the island. Exterior Websites Golden Gate National Parks
Conservancy: Golden Gate National Recreation Area: Wikipedia:
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Alcatraz Federal Penitentiary on top of
Alcatraz Island. |