San Francisco is also famous for Alcatraz Island, the site of
Alcatraz Prison, which - you guessed it - is made up of
Graywacke!
Graywacke is the result of turbidity flows that
are most often caused by Earthquakes. The Alcatraz Terrane is
bounded by a roughly diagonal line from near the foot of the San
Francisco anchorage of the Golden Gate Bridge to approximately Pier
48 in China Basin. Graywacke is also found in the San Bruno Terrane
in the South West part of San Francisco.
If you continue North from the posted coordinates, each
successive intersection will provide another interesting view of
Telegraph Hill and the Alcatraz Terrane. At the intersection of
Sansome and Filbert, you will find a set of stairs that leads up to
the top of Telegraph Hill, the home of San Francisco's
Wild
Parrots of Telegraph Hill!
To log this EarthCache: On the North West corner by the
coordinates is a commemorative plaque unrelated to the earthcache,
send an email to me with some facts from this plaque (proves you
were there). Post the number of people in your group and some
comments on your experience - for example, what do you see that
gives you some indication of the strength/weakness of Graywacke
(shows you thought about your visit)? You might want to post a
picture!
