San Francisco Bay
Overview
 
San Francisco Bay is a shallow, productive estuary
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

 through which water draining from approximately forty percent of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, flowing in the Sacramento
Sacramento River
The Sacramento River is an important watercourse of Northern and Central California in the United States. The largest river in California, it rises on the eastern slopes of the Klamath Mountains, and after a journey south of over , empties into Suisun Bay, an arm of the San Francisco Bay, and...

 and San Joaquin
San Joaquin River
The San Joaquin River is the largest river of Central California in the United States. At over long, the river starts in the high Sierra Nevada, and flows through a rich agricultural region known as the San Joaquin Valley before reaching Suisun Bay, San Francisco Bay, and the Pacific Ocean...

 river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

s from the Sierra Nevada mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...

s, enters the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

. Specifically, both rivers flow into Suisun Bay
Suisun Bay
Suisun Bay is a shallow tidal estuary at in northern California, USA. It lies at the confluence of the Sacramento and San Joaquin Rivers, forming the entrance to the Sacramento-San Joaquin River Delta, an inverted river delta...

, which flows through the Carquinez Strait
Carquinez Strait
The Carquinez Strait is a narrow tidal strait in northern California. It is part of the tidal estuary of the Sacramento and the San Joaquin rivers as they drain into the San Francisco Bay...

 to meet with the Napa River
Napa River
The Napa River, approximately 55 miles long, is a river in the U.S. state of California. It drains a famous wine-growing region, called the Napa Valley, in the mountains northeast of San Francisco. Milliken Creek is a tributary of the Napa River....

 at the entrance to San Pablo Bay
San Pablo Bay
San Pablo Bay is a tidal estuary that forms the northern extension of San Francisco Bay in northern California in the United States. Most of the Bay is shallow; however, there is a deep water channel approximately in mid bay, which allows access to Sacramento, Stockton, Benicia, Martinez, and...

, which connects at its south end to San Francisco Bay. However, the entire group of interconnected bays is often referred to as “San Francisco Bay”.

San Francisco Bay is located in the U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 state of California, surrounded by a contiguous region known as the San Francisco Bay Area
San Francisco Bay Area
The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...

 (often simply "the Bay Area"), dominated by the large cities San Francisco, Oakland
Oakland, California
Oakland is a major West Coast port city on San Francisco Bay in the U.S. state of California. It is the eighth-largest city in the state with a 2010 population of 390,724...

, and San Jose
San Jose, California
San Jose is the third-largest city in California, the tenth-largest in the U.S., and the county seat of Santa Clara County which is located at the southern end of San Francisco Bay...

.
Encyclopedia
San Francisco Bay is a shallow, productive estuary
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

 through which water draining from approximately forty percent of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, flowing in the Sacramento
Sacramento River
The Sacramento River is an important watercourse of Northern and Central California in the United States. The largest river in California, it rises on the eastern slopes of the Klamath Mountains, and after a journey south of over , empties into Suisun Bay, an arm of the San Francisco Bay, and...

 and San Joaquin
San Joaquin River
The San Joaquin River is the largest river of Central California in the United States. At over long, the river starts in the high Sierra Nevada, and flows through a rich agricultural region known as the San Joaquin Valley before reaching Suisun Bay, San Francisco Bay, and the Pacific Ocean...

 river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

s from the Sierra Nevada mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...

s, enters the Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

. Specifically, both rivers flow into Suisun Bay
Suisun Bay
Suisun Bay is a shallow tidal estuary at in northern California, USA. It lies at the confluence of the Sacramento and San Joaquin Rivers, forming the entrance to the Sacramento-San Joaquin River Delta, an inverted river delta...

, which flows through the Carquinez Strait
Carquinez Strait
The Carquinez Strait is a narrow tidal strait in northern California. It is part of the tidal estuary of the Sacramento and the San Joaquin rivers as they drain into the San Francisco Bay...

 to meet with the Napa River
Napa River
The Napa River, approximately 55 miles long, is a river in the U.S. state of California. It drains a famous wine-growing region, called the Napa Valley, in the mountains northeast of San Francisco. Milliken Creek is a tributary of the Napa River....

 at the entrance to San Pablo Bay
San Pablo Bay
San Pablo Bay is a tidal estuary that forms the northern extension of San Francisco Bay in northern California in the United States. Most of the Bay is shallow; however, there is a deep water channel approximately in mid bay, which allows access to Sacramento, Stockton, Benicia, Martinez, and...

, which connects at its south end to San Francisco Bay. However, the entire group of interconnected bays is often referred to as “San Francisco Bay”.

San Francisco Bay is located in the U.S.
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 state of California, surrounded by a contiguous region known as the San Francisco Bay Area
San Francisco Bay Area
The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...

 (often simply "the Bay Area"), dominated by the large cities San Francisco, Oakland
Oakland, California
Oakland is a major West Coast port city on San Francisco Bay in the U.S. state of California. It is the eighth-largest city in the state with a 2010 population of 390,724...

, and San Jose
San Jose, California
San Jose is the third-largest city in California, the tenth-largest in the U.S., and the county seat of Santa Clara County which is located at the southern end of San Francisco Bay...

. The waterway entrance to San Francisco Bay from the Pacific Ocean is called Golden Gate
Golden Gate
The Golden Gate is the North American strait connecting San Francisco Bay to the Pacific Ocean. Since 1937 it has been spanned by the Golden Gate Bridge...

. Across the strait spans the Golden Gate Bridge
Golden Gate Bridge
The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay into the Pacific Ocean. As part of both U.S. Route 101 and California State Route 1, the structure links the city of San Francisco, on the northern tip of the San Francisco Peninsula, to...

.

Size

The Bay covers somewhere between 400 and 1,600 square miles (1,040 to 4,160 square kilometers), depending on which sub-bays (such as San Pablo Bay), estuaries, wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....

s, and so on are included in the measurement. The main part of the Bay measures 3 to 12 miles (5 to 20 km) wide east-to-west and somewhere between 48 miles (77 km)1 and 60 miles (97 km)2 north-to-south. It is the largest Pacific estuary in North or South America.
The bay was navigable as far south as San Jose
San Jose, California
San Jose is the third-largest city in California, the tenth-largest in the U.S., and the county seat of Santa Clara County which is located at the southern end of San Francisco Bay...

 until the 1850s, when hydraulic mining
Hydraulic mining
Hydraulic mining, or hydraulicking, is a form of mining that uses high-pressure jets of water to dislodge rock material or move sediment. In the placer mining of gold or tin, the resulting water-sediment slurry is directed through sluice boxes to remove the gold.-Precursor - ground...

 released massive amounts of sediment from the rivers that settled in those parts of the bay that had little or no current. Later, wetlands and inlets were deliberately filled in, reducing the Bay's size since the mid-19th century by as much as one third. Recently, large areas of wetlands have been restored, further confusing the issue of the Bay's size. Despite its value as a waterway and harbor
Harbor
A harbor or harbour , or haven, is a place where ships, boats, and barges can seek shelter from stormy weather, or else are stored for future use. Harbors can be natural or artificial...

, many thousands of acre
Acre
The acre is a unit of area in a number of different systems, including the imperial and U.S. customary systems. The most commonly used acres today are the international acre and, in the United States, the survey acre. The most common use of the acre is to measure tracts of land.The acre is related...

s of marshy wetlands at the edges of the bay were, for many years, considered wasted space. 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.

From the mid-19th century through the late 20th century, more than a third of the original bay was filled and often built on. The deep, damp soil in these areas is subject to liquefaction during earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

s, and most of the major damage close to the Bay in the Loma Prieta earthquake
Loma Prieta earthquake
The Loma Prieta earthquake, also known as the Quake of '89 and the World Series Earthquake, was a major earthquake that struck the San Francisco Bay Area of California on October 17, 1989, at 5:04 p.m. local time...

 of 1989 occurred to structures on these areas.

The Marina District of San Francisco, hard hit by the 1989 earthquake, was built on fill that had been placed there for the Panama-Pacific International Exposition (1915)
Panama-Pacific International Exposition (1915)
The Panama-Pacific International Exposition was a world's fair held in San Francisco, California between February 20 and December 4 in 1915. Its ostensible purpose was to celebrate the completion of the Panama Canal, but it was widely seen in the city as an opportunity to showcase its recovery...

, although liquefaction did not occur on a large scale. In the 1990s, San Francisco International Airport
San Francisco International Airport
San Francisco International Airport is a major international airport located south of downtown San Francisco, California, United States, near the cities of Millbrae and San Bruno in unincorporated San Mateo County. It is often referred to as SFO...

 proposed filling in hundreds more acres to extend its overcrowded international runway
Runway
According to ICAO a runway is a "defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft." Runways may be a man-made surface or a natural surface .- Orientation and dimensions :Runways are named by a number between 01 and 36, which is generally one tenth...

s in exchange for purchasing other parts of the bay and converting them back to wetlands. The idea was, and remains, controversial. (For further details, see the "Bay Fill and Depth Profile" section.)

There are five large islands in San Francisco Bay. Alameda, the largest island, was created when a shipping lane was cut in 1901. It is now predominately a bedroom community. Angel Island
Angel Island, California
Angel Island is an island in San Francisco Bay that offers expansive views of the San Francisco skyline, the Marin County Headlands and Mount Tamalpais. The entire island is included within Angel Island State Park, and is administered by California State Parks. It has been used for a variety of...

 was known as "Ellis Island
Ellis Island
Ellis Island in New York Harbor was the gateway for millions of immigrants to the United States. It was the nation's busiest immigrant inspection station from 1892 until 1954. The island was greatly expanded with landfill between 1892 and 1934. Before that, the much smaller original island was the...

 West" because it served as the entry point for immigrants from East Asia
East Asia
East Asia or Eastern Asia is a subregion of Asia that can be defined in either geographical or cultural terms...

. It is now a state park accessible by ferry. Mountainous Yerba Buena Island
Yerba Buena Island
Yerba Buena Island sits in the San Francisco Bay between San Francisco and Oakland, California. The Yerba Buena Tunnel runs through its center and connects the western and eastern spans of the San Francisco-Oakland Bay Bridge. It has had several other names over the decades: Sea Bird Island, Wood...

 is pierced by a tunnel linking the east and west spans of the San Francisco – Oakland Bay Bridge. Attached to the north is the artificial and flat Treasure Island
Treasure Island, California
Treasure Island is an artificial island in the San Francisco Bay between San Francisco and Oakland, and an emerging neighborhood of San Francisco....

, site of the 1939 Golden Gate International Exposition
Golden Gate International Exposition
The Golden Gate International Exposition , held at San Francisco, California's Treasure Island, was a World's Fair that celebrated, among other things, the city's two newly-built bridges. The San Francisco – Oakland Bay Bridge was dedicated in 1936 and the Golden Gate Bridge was dedicated in 1937...

. From the Second World War until the 1990's, both islands served as military bases and are now being redeveloped. Isolated in the center of the Bay is Alcatraz, the site of the famous federal penitentiary. The federal prison on Alcatraz Island
Alcatraz Island
Alcatraz Island is an island located in the San Francisco Bay, offshore from San Francisco, California, United States. Often referred to as "The Rock" or simply "Traz", the small island was developed with facilities for a lighthouse, a military fortification, a military prison, and a Federal...

 no longer functions, but the complex is a popular tourist site. Despite its name, Mare Island
Mare Island
Mare Island is a peninsula in the United States alongside the city of Vallejo, California, about northeast of San Francisco. The Napa River forms its eastern side as it enters the Carquinez Strait juncture with the east side of San Pablo Bay. Mare Island is considered a peninsula because no full...

 in the northern part of the bay is a peninsula rather than an island.

Geology

San Francisco Bay is thought to represent a down-warping of the Earth's crust between the San Andreas Fault
San Andreas Fault
The San Andreas Fault is a continental strike-slip fault that runs a length of roughly through California in the United States. The fault's motion is right-lateral strike-slip...

 to the west and the Hayward Fault to the east, though the precise nature of this remains under study. During the last ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

, 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. The rivers of the Central Valley ran out to sea through a canyon that is now the Golden Gate. As the great ice sheets melted, sea level rose 300 feet (91.4 m) over 4,000 years, and the valley filled with water from the Pacific, becoming a bay. The small hills became islands.

History

The first recorded Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

an discovery of San Francisco Bay was on November 4, 1769 when Spanish
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

 explorer Gaspar de Portolà
Gaspar de Portolà
Gaspar de Portolà i Rovira was a soldier, governor of Baja and Alta California , explorer and founder of San Diego and Monterey. He was born in Os de Balaguer, province of Lleida, in Catalonia, Spain, of Catalan nobility. Don Gaspar served as a soldier in the Spanish army in Italy and Portugal...

, unable to find the port of Monterey, California
Monterey, California
The City of Monterey in Monterey County is located on Monterey Bay along the Pacific coast in Central California. Monterey lies at an elevation of 26 feet above sea level. As of the 2010 census, the city population was 27,810. Monterey is of historical importance because it was the capital of...

, continued north close to what is now Pacifica
Pacifica, California
Pacifica is a city in San Mateo County, California, on the coast of the Pacific Ocean between San Francisco and Half Moon Bay.-Overview:The City of Pacifica is spread along a six mile stretch of the north central California coastal beach and hills, nestled in several small valleys spanning between...

 and reached the summit of the 1200 feet (365.8 m) high Sweeney Ridge
Sweeney Ridge
Sweeney Ridge, a national park in Pacifica, California, is part of the Golden Gate National Recreation Area. Historically, the ridge was the location of the San Francisco Bay Discovery Site, as part of the Portolá Expedition on November 4, 1769.-Description:...

, where he sighted San Francisco Bay. Portola and his party did not realize what they had discovered, thinking they had arrived at a large arm of what is now called Drakes Bay
Drakes Bay
Drakes Bay is a small bay on the coast of northern California in the United States, approximately 30 miles northwest of San Francisco at approximately 38 degrees north latitude. The bay is approximately 8 miles wide...

. At the time, Drakes Bay went by the name Bahia de San Francisco and thus both bodies of water became associated with the name. Eventually, the larger, more important body of water fully appropriated the name San Francisco Bay.

The first European to enter the bay is believed to have been the Spanish explorer Juan de Ayala
Juan de Ayala
Juan Manuel de Ayala y Aranza was a Spanish naval officer who played a significant role in the European exploration of California, since he and the crew of his ship the San Carlos are the first Europeans known to have entered the San Francisco Bay.Ayala was born in Osuna, Andalucía...

, who passed through the Golden Gate
Golden Gate
The Golden Gate is the North American strait connecting San Francisco Bay to the Pacific Ocean. Since 1937 it has been spanned by the Golden Gate Bridge...

 on August 5, 1775 in his ship the San Carlos, and moored in a bay of Angel Island
Angel Island, California
Angel Island is an island in San Francisco Bay that offers expansive views of the San Francisco skyline, the Marin County Headlands and Mount Tamalpais. The entire island is included within Angel Island State Park, and is administered by California State Parks. It has been used for a variety of...

 now known as Ayala Cove.

This famous bay was the center of American settlement in the Far West during the 19th century. From the 1820s onward, American presidents and expansionists coveted the bay as a great natural harbor in the Pacific. After many failed efforts to buy the bay and varying areas around it, the US Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...

 and Army
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

 seized the region from Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 during the Mexican-American War (1845–1848). On February 2, 1848 California was annexed to the U.S. with the signing of the Treaty of Guadalupe Hidalgo
Treaty of Guadalupe Hidalgo
The Treaty of Guadalupe Hidalgo is the peace treaty, largely dictated by the United States to the interim government of a militarily occupied Mexico City, that ended the Mexican-American War on February 2, 1848...

. A year and a half later, California requested to join the United States on December 3, 1849 and was accepted as the 31st State of the union on September 9, 1850. During the California gold rush
Gold rush
A gold rush is a period of feverish migration of workers to an area that has had a dramatic discovery of gold. Major gold rushes took place in the 19th century in Australia, Brazil, Canada, South Africa, and the United States, while smaller gold rushes took place elsewhere.In the 19th and early...

 of 1848-1850s, San Francisco Bay instantly became one of the world's greatest seaports, dominating shipping and transportation in the American West until the last years of the 19th century. The bay's regional importance became paramount when the First Transcontinental Railroad
First Transcontinental Railroad
The First Transcontinental Railroad was a railroad line built in the United States of America between 1863 and 1869 by the Central Pacific Railroad of California and the Union Pacific Railroad that connected its statutory Eastern terminus at Council Bluffs, Iowa/Omaha, Nebraska The First...

 reached its western terminus in Alameda
Alameda, California
Alameda is a city in Alameda County, California, United States. It is located on Alameda Island and Bay Farm Island, and is adjacent to Oakland in the San Francisco Bay. The Bay Farm Island portion of the city is adjacent to the Oakland International Airport. At the 2010 census, the city had a...

 on September 6, 1869. The terminus was switched to the Oakland Long Wharf
Oakland Long Wharf
The Oakland Long Wharf, later known as the Oakland Pier or the SP Mole was a massive railroad wharf and ferry pier in Oakland, California. It was located at the foot of Seventh Street....

 two months later on November 8, 1869.

San Francisco Bay continues to support some of the densest industrial production and urban settlement in the United States. The San Francisco Bay Area is the American West's second-largest urban area with approximately 8 million residents.

Ecology

Despite its urban and industrial character, San Francisco Bay and the Sacramento-San Joaquin Delta
Sacramento River Delta
The Sacramento-San Joaquin River Delta, or California Delta, is an expansive inland river delta and estuary in northern California in the United States. The Delta is formed at the western edge of the Central Valley by the confluence of the Sacramento and San Joaquin rivers and lies just east of...

 remain perhaps California's most important ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

 habitats
Habitat (ecology)
A habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...

. California's Dungeness crab
Dungeness crab
The Dungeness crab, Metacarcinus magister , is a species of crab that inhabits eelgrass beds and water bottoms on the west coast of North America. It typically grows to across the carapace and is a popular seafood...

, California halibut
California halibut
The California halibut or California flounder, Paralichthys californicus, is a large-tooth flounder native to the waters of the Pacific Coast of North America from the Quillayute River in Washington to Magdalena Bay in Baja California. It feeds near shore and is free swimming. It typically weighs...

, and Pacific salmon
Oncorhynchus
Oncorhynchus is a genus of fish in the family Salmonidae; it contains the Pacific salmons and Pacific trouts. The name of the genus is derived from the Greek onkos and rynchos , in reference to the hooked jaws of males in the mating season .-Range:Salmon and trout with ranges generally in waters...

 fisheries rely on the bay as a nursery. The few remaining salt marsh
Salt marsh
A salt marsh is an environment in the upper coastal intertidal zone between land and salt water or brackish water, it is dominated by dense stands of halophytic plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh...

es now represent most of California's remaining salt marsh, supporting a number of endangered species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 and providing key ecosystem services such as filtering pollutants and sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

s from the rivers. San Francisco Bay is recognized for protection by the California Bays and Estuaries Policy
California Bays and Estuaries Policy
The Water Quality Control Policy for the Enclosed Bays and Estuaries of California is published by the California State Water Resources Control Board as guidelines to prevent water quality degradation. The policy is revised as needed.-Geography:...

.

Most famously, the bay is a key link in the Pacific Flyway
Pacific Flyway
The Pacific Flyway is a major north-south route of travel for migratory birds in America, extending from Alaska to Patagonia. Every year, migratory birds travel some or all of this distance both in spring and in fall, following food sources, heading to breeding grounds, or travelling to...

. Millions of waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....

 annually use the bay shallows as a refuge. Two endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...

 of birds are found here: the California least tern
California Least Tern
The Least Tern is a species of tern that breeds in North America and locally in northern South America. It is closely related to, and was formerly often considered conspecific with, the Little Tern of the Old World...

 and the California clapper rail
California Clapper Rail
The California Clapper Rail is an endangered subspecies of the Clapper Rail . It is found principally in California's San Francisco Bay, and also in Monterey Bay and Morro Bay...

. Exposed bay mud
Bay mud
Bay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are situated at the bottom of certain estuaries, which are normally in temperate regions that have experienced cyclical glacial cycles...

s provide important feeding areas for shorebirds, but underlying layers of bay mud pose geological hazards for structures near many parts of the bay perimeter. San Francisco Bay provided the nation's first wildlife refuge, Oakland's artificial Lake Merritt
Lake Merritt
Lake Merritt is a large tidal lagoon that lies just east of downtown Oakland, California. It is surrounded by parkland and city neighborhoods. A popular 3.1 mile walking and jogging path runs along its perimeter...

, constructed in the 1860s, and America's first urban National Wildlife Refuge, the Don Edwards San Francisco Bay National Wildlife Refuge
Don Edwards San Francisco Bay National Wildlife Refuge
Don Edwards San Francisco Bay National Wildlife Refuge is a US National Wildlife Refuge located in the southern part of San Francisco Bay, California. The Refuge headquarters and visitor center is located in the Baylands district of Fremont, next to Coyote Hills Regional Park, in Alameda County. ...

 (SFBNWR) in 1972. The Bay is also plagued by non-native species.

Salt produced from San Francisco Bay is produced in salt evaporation pond
Salt evaporation pond
Salt evaporation ponds, also called salterns or salt pans, are shallow artificial ponds designed to produce salts from sea water or other brines. The seawater or brine is fed into large ponds and water is drawn out through natural evaporation which allows the salt to be subsequently harvested...

s and is shipped throughout the Western United States to bakeries, canneries, fisheries, cheese makers and other food industries and used to de-ice winter highways, clean kidney dialysis machines, for animal nutrition, and in many industries.

Low-salinity salt ponds mirror the ecosystem of the bay, with fish and fish-eating birds in abundance. Mid-salinity ponds support dense populations of brine shrimp
Brine shrimp
Artemia is a genus of aquatic crustaceans known as brine shrimp. Artemia, the only genus in the family Artemiidae, has changed little externally since the Triassic period...

, which provide a rich food source for millions of shorebirds. Only salt-tolerant micro-algae survive in the high salinity ponds, and impart a deep red color to these ponds from the pigment within the algae protoplasm.

The seasonal range of water temperature in the Bay is from about 8 °C (46 °F) to about 23 °C (73 °F).

Humphrey the Whale
Humphrey the Whale
Humphrey the Whale is arguably the most widely publicized humpback whale in history, having errantly entered San Francisco Bay twice, departing from his Mexico to Alaska migration. This behavior is not normal for any Humpback whale, and Humphrey became well known on national television and press...

 entered San Francisco Bay twice on errant migrations, and was successfully rescued and redirected each time in the late 1980s and early 1990s. This occurred again with Dawn and Delta a mother and calf in 2007.

Industrial, mining, and other uses of mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

 have resulted in a widespread distribution in the bay, with uptake in the bay's phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...

 and contamination of its sportfish. In November 2007, a ship named COSCO Busan collided with the San Francisco – Oakland Bay Bridge and spilled over 58,000 gallons of bunker fuel, creating the largest oil spill
Oil spill
An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...

 in the region since 1996.

At times, San Francisco Bay is covered in fog
San Francisco Fog
San Francisco Fog Rugby Football Club , also known as "The Fog", is a rugby union football club in San Francisco, California. It is the first such team in the western United States established specifically to actively reach out to traditionally under-represented groups in rugby; such as people of...

.

For the first time in 65 years, Pacific Harbor Porpoise (Phocoena phocoena) returned to the Bay in 2009. 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. Pacific harbor porpoise range from Point Conception
Point Conception
Point Conception is a headland along the Pacific coast of U.S. state of California, located in southwestern Santa Barbara County. It is the point where the Santa Barbara Channel meets the Pacific Ocean, and as the corner between the mostly north-south trending portion of coast to the north and the...

, California to Alaska and across to the Kamchatka Peninsula
Kamchatka Peninsula
The Kamchatka Peninsula is a peninsula in the Russian Far East, with an area of . It lies between the Pacific Ocean to the east and the Sea of Okhotsk to the west...

 and Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

. Recent genetic studies show that there is a local stock from San Francisco to the Russian River and that eastern Pacific coastal populations rarely migrate far, unlike western Atlantic Harbor porpoise.

Bay fill and depth profile

San Francisco Bay's profile changed dramatically in the late 19th century and again with the initiation of dredging by the US Army Corps of Engineers in the 20th century. 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. 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
Hydraulic mining
Hydraulic mining, or hydraulicking, is a form of mining that uses high-pressure jets of water to dislodge rock material or move sediment. In the placer mining of gold or tin, the resulting water-sediment slurry is directed through sluice boxes to remove the gold.-Precursor - ground...

 operations into the upper Sacramento and San Joaquin Rivers. GK Gilbert's estimates of debris total more than eight times the amount of rock and dirt moved during construction of the Panama Canal. This material flowed down the rivers, progressively eroding into finer and finer sediment, until it reached the bay system. Here some of it settled, eventually filling in Suisun Bay, San Pablo Bay, and San Francisco Bay, in decreasing order of severity.

By the end of the 19th century, these "slickens" had filled in much of the shallow bay flats, raising the entire bay profile. New marshes were created in some areas.

In the last years of the nineteenth- and first decades of the twentieth-centuries, at the behest of local political officials and following Congressional orders, the US Army Corps began dredging the Sacramento and San Joaquin Rivers and the deep channels of San Francisco Bay. This work has continued without interruption ever since, an enormous federal subsidy of San Francisco Bay shipping. Some of the dredge spoils were initially dumped in the bay shallows (including helping to create Treasure Island
Treasure Island, California
Treasure Island is an artificial island in the San Francisco Bay between San Francisco and Oakland, and an emerging neighborhood of San Francisco....

 on the former shoals to the north of Yerba Buena Island
Yerba Buena Island
Yerba Buena Island sits in the San Francisco Bay between San Francisco and Oakland, California. The Yerba Buena Tunnel runs through its center and connects the western and eastern spans of the San Francisco-Oakland Bay Bridge. It has had several other names over the decades: Sea Bird Island, Wood...

) and used to raise an island in the Sacramento-San Joaquin Delta. 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. At the same time, most of the marsh areas have been filled or blocked off from the bay by dikes.

Large ships transiting the bay must follow deep underwater channels that are maintained by frequent dredging as the average depth of the Bay is as only as deep as a swimming pool--approximately 12 foot. Between Hayward
Hayward, California
Hayward is a city located in the East Bay in Alameda County, California. With a population of 144,186, Hayward is the sixth largest city in the San Francisco Bay Area and the third largest in Alameda County. Hayward was ranked as the 37th most populous municipality in California. It is included in...

 and San Mateo
San Mateo, California
San Mateo is a city in San Mateo County, California, United States, in the San Francisco Bay Area. With a population of approximately 100,000 , it is one of the larger suburbs on the San Francisco Peninsula, located between Burlingame to the north, Foster City to the east, Belmont to the south,...

 to San Jose
San Jose, California
San Jose is the third-largest city in California, the tenth-largest in the U.S., and the county seat of Santa Clara County which is located at the southern end of San Francisco Bay...

 it is 12 inch. The deepest part of the bay is under and out of the Golden Gate Bridge, at 300 ft (91.4 m).

Transportation

San Francisco Bay was traversed by watercraft since before the coming of Europeans; the indigenous peoples used their canoes to fish and clam along the shoreline. The era of sail brought ships that communicated with the rest of the world and served as early ferries and freighters within the Bay and between the Bay and inland ports such as Sacramento and Stockton. These were gradually replaced by steam-powered vessels starting in the late 19th century. Several shipyards were early established around the Bay, augmented during wartime. (See e.g. Kaiser Shipyards
Kaiser Shipyards
The Kaiser Shipyards were seven major shipbuilding yards located mostly on the U.S. west coast during World War II. They were owned by the Kaiser Shipbuilding Company, a creation of American industrialist Henry J...

)

San Francisco Bay is spanned by six bridges, five of them dedicated to vehicle traffic: the Golden Gate Bridge
Golden Gate Bridge
The Golden Gate Bridge is a suspension bridge spanning the Golden Gate, the opening of the San Francisco Bay into the Pacific Ocean. As part of both U.S. Route 101 and California State Route 1, the structure links the city of San Francisco, on the northern tip of the San Francisco Peninsula, to...

 (which was the largest single span suspension bridge
Suspension bridge
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century...

 ever built at the time of its construction), the Richmond-San Rafael Bridge
Richmond-San Rafael Bridge
The Richmond – San Rafael Bridge is the northernmost of the east–west crossings of the San Francisco Bay in California, USA, connecting Richmond on the east to San Rafael on the west end...

, the San Francisco – Oakland Bay Bridge, the Hayward-San Mateo Bridge, and the Dumbarton Bridge
Dumbarton Bridge (California)
The Dumbarton Bridge is the southernmost of the highway bridges that span the San Francisco Bay in California. Carrying over 81,000 vehicles daily, it is also the shortest bridge across San Francisco Bay at 1.63 miles...

. The sixth is the currently unused railroad bridge just south of the Dumbarton Bridge. The bay is also spanned by the Transbay Tube
Transbay Tube
The Transbay Tube is the part of BART which runs under San Francisco Bay in California. The tube is 3.6 miles long; including approaches from the nearest stations , it totals 6 miles...

, an underwater tunnel through which BART
Bay Area Rapid Transit
Bay Area Rapid Transit is a rapid transit system serving the San Francisco Bay Area. The heavy-rail public transit and subway system connects San Francisco with cities in the East Bay and suburbs in northern San Mateo County. BART operates five lines on of track with 44 stations in four counties...

 runs. Prior to the construction of these infrastructures, transbay transportation was dominated by fleets of ferryboats
Ferries of San Francisco Bay
San Francisco Bay in California has been served by ferries of all types for over 150 years. Although the construction of the Golden Gate Bridge and the San Francisco – Oakland Bay Bridge led to the decline in the importance of most ferries, some are still in use today for both commuters and...

 operated by the Southern Pacific Railroad
Southern Pacific Railroad
The Southern Pacific Transportation Company , earlier Southern Pacific Railroad and Southern Pacific Company, and usually simply called the Southern Pacific or Espee, was an American railroad....

 and the Key System
Key System
The Key System was a privately owned company which provided mass transit in the cities of Oakland, Berkeley, Alameda, Emeryville, Piedmont, San Leandro, Richmond, Albany and El Cerrito in the eastern San Francisco Bay Area from 1903 until 1960, when the system was sold to a newly formed public...

 transit company. However, in recent decades, ferries have returned, primarily serving commuters from Marin County, relieving the traffic bottleneck of the Golden Gate Bridge. (See article Ferries of San Francisco Bay
Ferries of San Francisco Bay
San Francisco Bay in California has been served by ferries of all types for over 150 years. Although the construction of the Golden Gate Bridge and the San Francisco – Oakland Bay Bridge led to the decline in the importance of most ferries, some are still in use today for both commuters and...

).

The Bay also continues to serve as a major international shipping port, served by a large container facility operated by the Port of Oakland
Port of Oakland
The Port of Oakland was the first major port on the Pacific Coast of the United States to build terminals for container ships. It is now the fifth busiest container port in the United States, behind Long Beach, Los Angeles, Newark, and Savannah...

, and two smaller facilities in Richmond and San Francisco.

Recreation

San Francisco Bay is a mecca for sailors (boats, as well as windsurfing
Windsurfing
Windsurfing or sailboarding is a surface water sport that combines elements of surfing and sailing. It consists of a board usually two to four metres long, powered by the orthogonal effect of the wind on a sail. The rig is connected to the board by a free-rotating universal joint and comprises a...

 and kitesurfing
Kitesurfing
Kitesurfing or Kiteboarding is an adventure surface water sport that has been described as combining wakeboarding, windsurfing, surfing, paragliding, and gymnastics into one extreme sport. Kitesurfing harnesses the power of the wind to propel a rider across the water on a small surfboard or a...

), due to consistent strong westerly/northwesterly thermally-generated winds (Beaufort force
Beaufort scale
The Beaufort Scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort Wind Force Scale.-History:...

 6 (15-25 knots) is common on summer afternoons) and protection from large open ocean swells. Yachting
Yachting
Yachting refers to recreational sailing or boating, the specific act of sailing or using other water vessels for sporting purposes.-Competitive sailing:...

 and yacht racing
Yacht racing
Yacht racing is the sport of competitive yachting.While sailing groups organize the most active and popular competitive yachting, other boating events are also held world-wide: speed motorboat racing; competitive canoeing, kayaking, and rowing; model yachting; and navigational contests Yacht racing...

 are popular pastimes and the San Francisco Bay Area is home to many of the world's top sailors. A shoreline bicycle and pedestrian trail known as the San Francisco Bay Trail
San Francisco Bay Trail
The San Francisco Bay Trail is a bicycle and pedestrian trail that will eventually allow continuous travel around the shoreline of San Francisco Bay. As of 2011, approximately 310 miles of trail have been completed...

 encircles the edge of the bay. Parks and protected areas around the bay include Eden Landing Ecological Reserve
Eden Landing Ecological Reserve
Eden Landing Ecological Reserve is a nature reserve in Hayward and Union City, California, on the eastern shore of San Francisco Bay. The reserve is managed by the California Department of Fish and Game, and comprises 5,040 acres of former industrial salt ponds now used as a low salinity waterbird...

, Hayward Regional Shoreline
Hayward Regional Shoreline
Hayward Regional Shoreline is a regional park located on the shores of the San Francisco Bay in Hayward, California. It is part of the East Bay Regional Parks system. The park extends to the shores of San Lorenzo. Part of the park is former commercial salt flats purchased in 1996. A former...

, Don Edwards San Francisco Bay National Wildlife Refuge
Don Edwards San Francisco Bay National Wildlife Refuge
Don Edwards San Francisco Bay National Wildlife Refuge is a US National Wildlife Refuge located in the southern part of San Francisco Bay, California. The Refuge headquarters and visitor center is located in the Baylands district of Fremont, next to Coyote Hills Regional Park, in Alameda County. ...

, Hayward Shoreline Interpretive Center
Hayward Shoreline Interpretive Center
The Hayward Shoreline Interpretive Center is a natural history and ecology interpretive nature center located in Hayward, California. It is directly adjacent to the north side of Highway 92 as it approaches the San Mateo – Hayward Bridge, and is accessed from the highway by the last offramp in the...

, Crown Memorial State Beach
Crown Memorial State Beach
Crown Memorial State Beach is a state park in the city of Alameda, CA on the shores of the San Francisco Bay. It is operated by the East Bay Regional Parks District....

, Eastshore State Park
Eastshore State Park
Eastshore State Park is a state park and wildlife refuge along the San Francisco Bay shoreline of the East Bay between the cities of Richmond, Albany, Berkeley, Emeryville, and Oakland. It encompasses remnant natural wetlands, restored wetlands as well as landfill west of the Eastshore Freeway. It...

, Point Isabel Regional Shoreline
Point Isabel Regional Shoreline
Point Isabel Regional Shoreline in Richmond, California, operated by East Bay Regional Park District, is an award-winning park offering activities for humans as well as dogs. It also features a concession offering food for humans and grooming for pets. It has easy access for pedestrians, public...

, Brooks Island Regional Shoreline, and César Chávez Park
César Chávez Park
César Chávez Park is a city park of Berkeley, California named after César Chávez. It can be found on the peninsula on the north side of the Berkeley Marina in the San Francisco Bay and is adjacent to Eastshore State Park....

.

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. The California Coastal Conservancy approved funding in March 2011 to begin implementation of the water trail.

Kitesurfing
Kitesurfing
Kitesurfing or Kiteboarding is an adventure surface water sport that has been described as combining wakeboarding, windsurfing, surfing, paragliding, and gymnastics into one extreme sport. Kitesurfing harnesses the power of the wind to propel a rider across the water on a small surfboard or a...

 and wind surfing are also popular in the bay.

See also

  • Islands of San Francisco Bay
  • Golden Gate
    Golden Gate
    The Golden Gate is the North American strait connecting San Francisco Bay to the Pacific Ocean. Since 1937 it has been spanned by the Golden Gate Bridge...

  • Mount Tamalpais State Park
    Mount Tamalpais
    Mount Tamalpais is a peak in Marin County, California, United States, often considered symbolic of Marin County. Much of Mount Tamalpais is protected within public lands such as Mount Tamalpais State Park and the Mount Tamalpais Watershed.-Geography:...

  • Mount Diablo State Park
  • Napa Sonoma Marsh
    Napa Sonoma Marsh
    The Napa Sonoma Marsh is a wetland at the northern edge of San Pablo Bay, which is a northern arm of the San Francisco Bay in California, USA. This marsh has an area of 48,000 acres , of which 13,000 acres are abandoned salt evaporation ponds...

  • Point Pinole Regional Shoreline
    Point Pinole Regional Shoreline
    The Point Pinole Regional Shoreline is a regional park on the shores of the San Pablo Bay, California . It is approximately in area, and is operated by the East Bay Regional Park District.-History:...

    , Richmond
  • Eastshore State Park
    Eastshore State Park
    Eastshore State Park is a state park and wildlife refuge along the San Francisco Bay shoreline of the East Bay between the cities of Richmond, Albany, Berkeley, Emeryville, and Oakland. It encompasses remnant natural wetlands, restored wetlands as well as landfill west of the Eastshore Freeway. It...

  • Hydrography of the San Francisco Bay Area
    Hydrography of the San Francisco Bay Area
    The Hydrography of the San Francisco Bay Area is a complex network of watersheds, marshes, rivers, creeks, reservoirs, and bays predominantly draining into the San Francisco Bay and Pacific Ocean.-Bays:...



People
  • J.C. Barthel
    J.C. Barthel
    Julius C. Barthel, who went by J.C. Barthel, was an engineer and politician who was a Los Angeles City Council member from 1929 to 1931.-Biography:...

    , who prepared "plans for the docks and other water-front improvements in the San Francisco Bay district"

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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