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. The San Francisco Bay Area Water Trail is a planned system of designated trailheads designed to improve non-motorized small boat access to the bay. From the Second World War until the 1990s, both islands served as military bases and are now being redeveloped. During the last ice age, the basin now filled by the bay was a large linear valley with small hills, similar to most of the valleys of the Coast Ranges. San Francisco Bay is a shallow estuary in the U.S. state of California. 1. The Bay also continues to serve as a major international shipping port, served by a large container facility operated by the Port of Oakland, and two smaller facilities in Richmond and San Francisco. In November 2007, a ship named COSCO Busan collided with the San Francisco–Oakland Bay Bridge and spilled over 58,000 US gallons (220,000 litres)* of bunker fuel, creating the largest oil spill in the region since 1996. If you’ve ever had a kid rattle off a million facts about seagulls, you know they are total sponges for any sort of trivia. However, this entire group of interconnected bays is often called the San Francisco Bay. Some of the dredge spoils were initially dumped in the bay shallows (including helping to create Treasure Island on the former shoals to the north of Yerba Buena Island) and used to raise an island in the Sacramento-San Joaquin Delta. It is now predominantly a bedroom community. Prior to the bridges and, later, the Transbay Tube, transbay transportation was dominated by fleets of ferryboats operated by the Southern Pacific Railroad and the Key System transit company. Yachting and yacht racing are popular pastimes and the San Francisco Bay Area is home to many of the world's top sailors. For the geographical region surrounding the San Francisco Bay, see, San Francisco Bay, San Pablo Bay, and the Golden Gate, Barging In - A Short History of Liveaboards on the Bay, Army Corps of Engineers Bay Model: Working scale model of the Bay, Photos of SF Bay and its boats, plus online cruising guide, SF Estuary Institute: San Francisco Bay Historical View Maps, Despite its urban and industrial character, San Francisco Bay and the Sacramento-San Joaquin Delta remain perhaps California's most important ecological habitats. It is now a state park accessible by ferry. Many companies have produced salt in the Bay, with the Leslie Salt Company the largest private land owner in the Bay Area in the 1940s. Most famously, the bay is a key link in the Pacific Flyway. Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox. It then connects to the Pacific Ocean via the Golden Gate strait. Golden Gate Cetacean Research, a non-profit organization focused on research on cetaceans, has developed a photo-identification database enabling the scientists to identify specific porpoise individuals and is trying to ascertain whether a healthier bay has brought their return. Angel Island was known as "Ellis Island West" because it served as the entry point for immigrants from East Asia. San Francisco Bay is spanned by eight bridges, all dedicated to vehicle traffic. The seasonal range of water temperature in the Bay is from January's 53 °F (12 °C) to September's 60 °F (16 °C) when measured at Fort Point, which is near the southern end of the Golden Gate Bridge and at the entrance to San Francisco Bay. (See article Ferries of San Francisco Bay). The Antioch Bridge on SR 160 connects Contra Costa and Sacramento counties. Large ships transiting the bay must follow deep underwater channels that are maintained by frequent dredging as the average depth of the bay is only as deep as a swimming pool—approximately 12 to 15 ft (4–5 m). In January 1971, two Standard Oil tankers collided in the bay, creating an 800,000-US-gallon (3,000,000-litre)* oil spill disaster, which spurred environmental protection of the bay. San Francisco Bay is 60 miles (97 km) long and 3 to 12 miles (5 to 19 km) wide and is one of the world’s finest natural harbours. The deepest part of the bay is under and out of the Golden Gate Bridge, at 372 ft (113 m). San Francisco Bay, large, nearly landlocked bay indenting western California, U.S. Here some of it settled, eventually filling in Suisun Bay, San Pablo Bay, and San Francisco Bay, in decreasing order of severity. Indigenous peoples used canoes to fish and clam along the shoreline. The first European to see San Francisco Bay is likely N. de Morena who was left at New Albion at Drakes Bay in Marin County, California by Sir Francis Drake in 1579 and then walked to Mexico. Millions of waterfowl annually use the bay shallows as a refuge. This dredging enabled the arrival of the largest container ship ever to enter the San Francisco Bay, the MSC Fabiola. Some content of the original page may have been edited to make it more suitable for younger readers, unless otherwise noted. Attached to the north is the artificial and flat Treasure Island, site of the 1939 Golden Gate International Exposition. Updates? The small hills became islands. As a result, soil excavated for building projects or dredged from channels was often dumped onto the wetlands and other parts of the bay as landfill. The deep, damp soil in these areas is subject to soil liquefaction during earthquakes, and most of the major damage close to the Bay in the Loma Prieta earthquake of 1989 occurred to structures on these areas. San Francisco Bay is a shallow, productive estuary through which water draining about forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains and Central Valley, enters the Pacific Ocean. This news created the Save the Bay movement in 1960, which mobilized to stop the infill of wetlands and the bay in general, which had shrunk to two-thirds of its size in the century before 1961. Isolated in the center of the Bay is Alcatraz, the site of the famous federal penitentiary. For the first time in 65 years, Pacific Harbor Porpoise (Phocoena phocoena) returned to the Bay in 2009. According to Census and Animal Care and Control department data, San Francisco has around 10,000 more ... 2. The bay's regional importance increased further when the First Transcontinental Railroad was connected to its western terminus at Alameda on September 6, 1869. Area 46 square miles (120 square km). Ayala continued to explore the Bay area and the expedition's cartographer, José de Cañizares, gathered the information necessary to produce the first map of the San Francisco Bay area. The Benicia Bridge on I-680 also connects Contra Costa and Solano counties. (For further details, see the "Bay Fill and Depth Profile" section.). San Francisco Bay drains water from approximately 40 percent of California. These were gradually replaced by steam-powered vessels starting in the late 19th century. San Francisco Bay is thought to represent a down-warping of the Earth's crust between the San Andreas Faultto the west and the Hayward Fault to the east, though the precise nature of this remains under study. Before about 1860, most bay shores (exception: rocky shores such as those in Carquinez Strait, along Marin shoreline, Point Richmond, Golden Gate area) contained extensive wetlands that graded nearly invisibly from freshwater wetlands to salt marsh and then tidal mudflat. Technically, both rivers flow into Suisun Bay, which help flows through the Carquinez Strait to meet with the Napa River at the entrance to San Pablo Bay, which connects at its south end to San Francisco Bay, although the entire group of interconnected bays are often referred to as "the San Francisco Bay.". The rivers of the Central Valley ran out to sea through a canyon that is now the Golden Gate. A deep channel ran through the center of the bay, following the ancient drowned river valley. In the 1860s and continuing into the early 20th century, miners dumped staggering quantities of mud and gravel from hydraulic mining operations into the upper Sacramento and San Joaquin Rivers. Announcing our NEW encyclopedia for Kids! The net effect of dredging has been to maintain a narrow deep channel—deeper perhaps than the original bay channel—through a much shallower bay.