Geology of Bolinas Bay/Stinson Beach California

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Fault lines, landslides, and beautiful beaches - the geology of Bolinas & Stinson Beach is pretty much California in a nutshell. Take a virtual field trip of Bolinas/Stinson Beach geology or try it out yourself. Here are the stops:

Stop 1: Agate Beach. https://www.marincountyparks.org/park...
Check out the amazing cliffs of Santa Cruz Mudstone - bonus points if you get there during low tide to see step-like patterns formed from alternating layers of stronger and weaker rock.

Stop 2: Bolinas Beach. https://www.californiabeaches.com/bea... The rock at Bolinas Beach is several million years younger than at Agate Beach due to movement along the San Gregorio and San Andreas Faults. You can see the exact same rock at Mussel Rock Park in San Francisco over 20 miles away.

Stop 3: Stinson Beach. https://www.nps.gov/goga/stbe.htm Learn about longshore drift as you walk along this massive sand spit and make sure to check out Bolinas Lagoon behind Stinson. The San Andreas Fault cuts through both features toward the west end of the beach.

Stop 4: Highway 1 Landslides. Drive south on Highway 1 out of Stinson Beach. Park where safe to do so along one of the curves and look at the cliffs for signs of a landslide - there are many to find here. The largest one is at Slide Ranch.

References:
Bigelow et al., 2001, Bolinas Lagoon Watershed Study
Input Sediment Budget, Report prepared for US Army Corps of Engineers

Cochrane, G.R., Dartnell, Peter, Johnson, S.Y., Greene, H.G., Erdey, M.D., Golden, N.E., Hartwell, S.R., Manson, M.W., Sliter, R.W., Endris, C.A., Watt, J.T., Ross, S.L., Kvitek, R.G., Phillips, E.L., Bruns, T.R., and Chin, J.L., 2015, California State Waters Map Series: offshore of Bolinas, California: U.S. Geological Survey, Open-File Report OF-2015-1135, scale 1:24,000

Edwards, B.D., Phillips, E.L., Dartnell, P., Greene, H.G., Bretz, C.K., Kvitek, R.G., Hartwell, S.R., Johnson, S.Y., Cochrane, G.R., Dieter, B.E., Sliter, R.W., Ross, S.L., Golden, N.E., Watt, J.T., Chin, J.L., Erdey, M.D., Krigsman, L.M., Manson, M.W., and Endris, C.A., 2014, California State Waters Map Series—offshore of Pacifica, California: U.S. Geological Survey, Open-File Report OF-2014-1260, scale 1:24,000

Konigsmark, T., 1998, Geologic Trips: San Francisco and the Bay Area, GeoPress

0:00 Introduction
0:07 Agate Beach
1:54 Jalama Beach
2:02 Bolinas Beach
2:17 San Gregorio Fault
2:42 Pliocene-Pleistocene
3:25 Stinson Beach
5:21 Stinson = North American Plate
5:24 Highway 1 Landslides
5:54 Slide Ranch