Editing San Francisco Bay (section)

==Geology==
[[File:Urban-Rural Population and Land Area Estimates, v2, 2010 San Francisco Bay, U.S. (13874137664).jpg|thumb|Population density and low elevation coastal zones in San Francisco Bay (2010). The San Francisco Bay is especially vulnerable to [[sea level rise]].]]
San Francisco Bay is thought to represent a down-warping of the Earth's crust between the [[San Andreas Fault]] to the west and the [[Hayward Fault]] to the east, though the precise nature of this remains under study. About 560,000 years ago, a [[Tectonics|tectonic]] shift caused the large inland [[Lake Corcoran]] to spill out the [[Central Valley (California)|central valley]] and through the [[Carquinez Strait]], carving out sediment and forming canyons in what is now the northern part of the San Francisco Bay and [[Golden Gate|Golden Gate strait]].<ref>{{cite web |title=The Formation of San Francisco Bay |url=http://education.savingthebay.org/wp-content/guides/The-Formation-of-San-Francisco-Bay.pdf |publisher=KQED education |access-date=June 4, 2018 |archive-date=July 19, 2014 |archive-url=https://web.archive.org/web/20140719092249/http://education.savingthebay.org/wp-content/guides/The-Formation-of-San-Francisco-Bay.pdf |url-status=live }}</ref>

San Francisco Bay has been filled and emptied of sea water many times during the Pleistocene in accordance with sea level changes caused by glacial advances and retreats.<ref name="geotrip">{{Cite book |last=Konigsmark |first=Ted |url=https://archive.org/details/geologictripssan0000koni |title=Geologic Trips San Francisco and the Bay Area |publisher=GeoPress |year=1998 |isbn=0-9661316-4-9 |location=Gualala, California |chapter=Fort Funston |chapter-url=https://www.geologictrips.com/sf/sfttff.pdf}}</ref> During the [[Wisconsin glaciation|Wisconsin Glaciation]], between 15,000 and about 10,000 years ago, the basin which is now filled by the San Francisco Bay was a large river valley with small hills, channeling the [[Sacramento River]] through the [[Golden Gate Strait]] into the ocean.<ref name="geotrip" /> When the great ice sheets began to melt, around 11,000 years ago, the sea level started to rise rapidly, by about 1 inch per year.<ref name="save bay" /> Melting glaciers in the Sierra Nevada washed huge amounts of sediment down the Sacramento and San Joaquin rivers, which accumulated on the shores of the bay, forming huge mudflats and marshes that supported local wildlife.<ref name="save bay" /> By 5000&nbsp;BC the sea level rose {{convert|300|ft|m|-1}}, filling the valley with water from the Pacific.<ref name="save bay">{{cite web |last1=Yabrove |first1=Daniel |title=How the Bay was Born |url=https://blog.savesfbay.org/2013/12/how-the-bay-was-born/ |website=Save The Bay Blog |publisher=Save The Bay |access-date=June 4, 2018 |date=December 9, 2013 |archive-date=June 20, 2018 |archive-url=https://web.archive.org/web/20180620153215/https://blog.savesfbay.org/2013/12/how-the-bay-was-born/ |url-status=dead }}</ref> The [[Farallon Islands]] are what used to be hills along the old coastline,<ref name="save bay" /> and Potato Patch Shoal is an area of sand dunes now covered by the ocean.<ref name="geotrip" />