The Chesapeake Bay ( ) is the largest estuary in the United States. The bay is located in the Mid-Atlantic region and is primarily separated from the Atlantic Ocean by the Delmarva Peninsula, including parts of the Eastern Shore of Maryland, the Eastern Shore of Virginia, and the state of Delaware. The mouth of the bay at its southern point is located between Cape Henry and Cape Charles. With its northern portion in Maryland and the southern part in Virginia, the Chesapeake Bay is a very important feature for the ecology and economy of those two states, as well as others surrounding within its watershed. More than 150 major rivers and streams flow through the bay's drainage basin, which covers parts of six states (New York, Pennsylvania, Delaware, Maryland, Virginia, and West Virginia) and all of Washington, D.C.
The bay is approximately long from its northern headwaters in the Susquehanna River to its outlet in the Atlantic Ocean. It is wide at its narrowest (between Kent County's Plum Point near Newtown in the east and the Harford County western shore near Romney Creek) and at its widest (just south of the mouth of the Potomac River, which divides Maryland from Virginia). Its total shoreline including tributaries is , surrounding a surface area of . Average depth is , reaching a maximum of . The bay is spanned twice, in Maryland by the Chesapeake Bay Bridge from Sandy Point (near Annapolis) to Kent Island and in Virginia by the Chesapeake Bay Bridge–Tunnel connecting Virginia Beach to Cape Charles.
Known for both its beauty and bounty, the bay has become "emptier", with fewer crabs, oysters and watermen (fishermen) since the mid-20th century. Nutrient pollution and urban runoff have been identified as major components of impaired water quality in the bay, stressing ecosystems and compounding the decline of shellfish due to overharvesting. Restoration efforts that began in the 1990s have continued into the 21st century and show potential for growth of the native oyster population. The health of the Chesapeake Bay improved in 2015, marking three years of gains over a four-year period. Slight improvements in water quality were observed in 2021, compared to indicators measured in 2020. The bay is experiencing other environmental concerns, including climate change, which is causing sea level rise that erodes coastal areas and infrastructure and changes the marine ecosystem.
Etymology The word is an Algonquian word referring to a village 'at a big river'. It is the seventh-oldest surviving English placename in the United States, first applied as Chesepiook by explorers heading north from the Roanoke Colony into a Chesapeake tributary in 1585 or 1586. The name may also refer to the Chesapeake people or the Chesepian, a Native American tribe who inhabited the area now known as South Hampton Roads in the U.S. state of Virginia. They occupied an area that is now the Norfolk, Portsmouth, Chesapeake, and Virginia Beach areas.Also shown as Chisupioc (by John Smith) and Chisapeack, in Algonquian means 'big' or 'great', means river, and the or ending indicated something (a village, in this case) 'at' that feature. is also found in another placename of Algonquian origin, Mississippi. The name was soon transferred by the English from the big river and the village at that site to the entire bay. In 2005, Algonquian linguist Blair Rudes "helped to dispel one of the area's most widely held beliefs: that 'Chesapeake' means something like 'great shellfish bay'. It does not, Rudes said. The name might have actually meant something like 'great water', or it might have just referred to a village location at the bay's mouth."
The first European name for the bay was "Bahia de Santa Maria" (St. Mary's bay). This name was coined by the Spanish.
Physical geography Geology and formation
The Chesapeake Bay is an estuary to the North Atlantic, lying between the Delmarva Peninsula to the east and the North American mainland to the west. It is the ria, or drowned valley, of the Susquehanna River, meaning that it was the alluvial plain where the river flowed when the sea level was lower. It is not a fjord, because the Laurentide Ice Sheet never reached as far south as the northernmost point on the bay. North of Baltimore, the western shore borders the hilly Piedmont region of Maryland; south of the city the bay lies within the state's low-lying coastal plain, with sedimentary cliffs to the west, and flat islands, winding creeks and marshes to the east. The large rivers entering the bay from the west have broad mouths and are extensions of the main ria for miles up the course of each river.
The bay's geology, its present form, and its very location were created by a bolide impact event at the end of the Eocene (about 35.5 million years ago), forming the Chesapeake Bay impact crater and much later the Susquehanna River valley. The bay was formed starting about 10,000 years ago when rising sea levels at the end of the last ice age flooded the Susquehanna River valley. Parts of the bay, especially the Calvert County, Maryland, coastline, are lined by cliffs composed of deposits from receding waters millions of years ago. These cliffs, generally known as Calvert Cliffs, are famous for their fossils, especially fossilized shark teeth, which are commonly found washed up on the beaches next to the cliffs. Scientists' Cliffs is a beach community in Calvert County named for the desire to create a retreat for scientists when the community was founded in 1935.
Hydrology
Much of the bay is shallow. At the point where the Susquehanna River flows into the bay, the average depth is , although this soon diminishes to an average of southeast of the city of Havre de Grace, Maryland, to about just north of Annapolis. On average, the depth of the bay is , including tributaries; Other sources give values of 25 feet (e.g. ) or deep () over 24 percent of the bay is less than deep.
Because the bay is an estuary, it has fresh water, salt water and brackish water. Brackish water has three salinity zones: oligohaline, mesohaline, and polyhaline. The freshwater zone runs from the mouth of the Susquehanna River to north Baltimore. The oligohaline zone has very little salt. Salinity varies from 0.5 ppt (parts per thousand) to 10 ppt, and freshwater species can survive there. The north end of the oligohaline zone is north Baltimore and the south end is the Chesapeake Bay Bridge. The mesohaline zone has a medium amount of salt and runs from the Bay Bridge to the mouth of the Rappahannock River. Salinity there ranges from 1.07% to 1.8%. The polyhaline zone is the saltiest zone, and some of the water can be as salty as sea water. It runs from the mouth of the Rappahannock River to the mouth of the bay. The salinity ranges from 1.87% to 3.6%. (3.6% is as salty as the ocean.)
The climate of the area surrounding the bay is primarily humid subtropical, with hot, very humid summers and cold to mild winters. Only the area around the mouth of the Susquehanna River is continental in nature, and the mouth of the Susquehanna River and the Susquehanna flats often freeze in winter. It is rare for the surface of the bay to freeze in winter, something that happened most recently in the winter of 1976–77.
The Chesapeake Bay is the end point of over 150 rivers and streams. The largest rivers flowing directly into the bay, in order of discharge, are the Susquehanna River, Potomac River, James River, Rappahannock River, York River, Patuxent River, and Choptank River.
For more information on Chesapeake Bay rivers, see the List of Chesapeake Bay rivers.
Flora and fauna
The Chesapeake Bay is home to numerous fauna that either migrate to the bay at some point during the year or live there year-round. There are over 300 species of fish and numerous shellfish and crab species. Some of these include the Atlantic menhaden, striped bass, American eel, eastern oyster, Atlantic horseshoe crab, and the blue crab.
Birds include ospreys, great blue herons, bald eagles, and peregrine falcons, the last two of which were threatened by DDT; their numbers plummeted but have risen in recent years. The piping plover is a near threatened species that inhabits the wetlands.
Larger fish such as Atlantic sturgeon, varieties of sharks,The Chesapeake Bay News. 2010. Are there sharks in the Chesapeake Bay?. Retrieved on December 21. 2014 and stingrays visit the bay. The waters of the Chesapeake Bay have been regarded as one of the most important nursery areas for sharks along the east coast.The National Aquarium. Sharks Among Us: Chesapeake Bay Species . Retrieved on December 22. 2014 Megafaunas such as bull sharks, tiger sharks, scalloped hammerhead sharks, and basking sharks and manta rays are also known to visit. Smaller species of sharks and stingrays that are known to be regular to occasional residents in the bay include the smooth dogfish, spiny dogfish, cownose ray, and bonnethead.
Bottlenose dolphins are known to live seasonally/yearly in the bay. There have been unconfirmed sightings of humpback whales in recent years.The Southside Sentinel. 2010. Whale sighted in the Chesapeake Bay . Retrieved on December 21. 2014 Endangered North Atlantic right whaleNational Oceanic and Atmospheric Administration. 2010. NOAA: Ship Speed Restrictions to Protect Endangered North Atlantic Right Whales. Retrieved on December 22. 2014, fin, minke, and sei whales have also been sighted within and in the vicinity of the bay.
A male manatee visited the bay several times between 1994 and 2011, even though the area is north of the species' normal range. The manatee, recognizable due to distinct markings on its body, was nicknamed "Chessie" after a legendary sea monster that was allegedly sighted in the bay during the 20th century. The same manatee has been spotted as far north as Rhode Island, and was the first manatee known to travel so far north. Other manatees are occasionally seen in the bay and its tributaries, which contain sea grasses that are part of the manatee's diet.
Loggerhead turtles are known to visit the bay.
The Chesapeake Bay is also home to a diverse flora, both land and aquatic. Common submerged aquatic vegetation includes eelgrass and widgeon grass. A report in 2011 suggested that information on underwater grasses would be released, because "submerged grasses provide food and habitat for a number of species, adding oxygen to the water and improving water clarity." Other vegetation that makes its home in other parts of the bay are wild rice, various trees like the red maple, loblolly pine and bald cypress, and spartina grass and phragmites.Domes S., Lewis M., Moran R., Nyman D.. "Chesapeake Bay Wetlands". Emporia State University. May 2009. Retrieved 2010-03-14. Invasive plants have taken a significant foothold in the bay. Plants such as Phragmites, Purple loosestrife and Japanese stiltgrass have established high levels of permanency in Chesapeake wetlands. Additionally, plants such as Brazilian waterweed, native to South America, have spread to most continents with the help of aquarium owners, who often dump the contents of their aquariums into nearby lakes and streams. It is highly invasive and has the potential to flourish in the low-salinity tidal waters of the bay. Dense stands of Brazilian waterweed can restrict water movement, trap sediment and affect water quality. Various local K-12 schools in the Maryland and Virginia region often have programs that cultivate native bay grasses and plant them in the bay.
History Pre-Columbian