Chesapeake Bay ( ) is the largest estuary in the United States. It lies off the Atlantic Ocean, surrounded by Maryland and Virginia.
Chesapeake Bay's watershed covers in
the District of
Columbia and parts of six states: New York, Pennsylvania, Delaware, Maryland, Virginia, and
than 150 rivers and streams drain into the Bay.
The Chesapeake Bay is approximately 200 miles (300 km) long,
from the Susquehanna River
north to the Atlantic Ocean in the south. At its narrowest point
County's Plum Point (near Newtown) and the Harford
County shore near Romney Creek, the Bay is 2.8 miles
(4.5 km) wide; at its widest point, just south of the mouth of
the Potomac River, it is 30 miles
(50 km) wide.
Total shoreline for the Bay and its
tributaries is 11,684 miles (18,804 km), and the surface area
of the bay and its major tributaries is . Depth of the bay is and
maximum depth of bay is .
The bay is spanned in two places. The Chesapeake Bay Bridge crosses the bay in Maryland from Sandy Point (near
Annapolis) to Kent Island; the Chesapeake Bay Bridge-Tunnel in
Virginia connects Virginia Beach to Cape Charles.
The word Chesepiooc
is an Algonquian
word referring to a village "at a big
river." It is the seventh oldest surviving English place-name in
the U.S., first applied as "Chesepiook" by explorers heading north
from the Roanoke Colony
Chesapeake tributary in 1585 or 1586. 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 doesn't, Rudes said. The name might actually mean
something like 'Great Water,' or it might have been just a village
at the bay's mouth." In contrast with many similar bodies of water, such as Delaware Bay or San Francisco Bay, the Chesapeake Bay is almost always preceded by
the article the in usage.
The Chesapeake Bay is the ria
, or drowned
valley, of the Susquehanna, meaning that it was where the river
flowed when the sea level was lower. It is not a fjord
, as the Laurentide Ice Sheet
never reached as
far south as the northernmost point on the bay.
geology, its present form, and its very location were created by a
event at the end of the Eocene (about
35.5 million years ago), forming the Chesapeake Bay
impact crater and the Susquehanna river valley much later.
The Bay itself 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.
Much of the bay is quite shallow. At the point where the Susquehanna River
flows into the bay, the average depth is , although this soon
diminishes to an average of from the city of Havre de
Grace for about , to just north of Annapolis.
average, the depth of the bay is 21 feet (7 meters), including
tributaries; over 24% of the bay is less than deep.
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 exceedingly rare for the surface of the bay to freeze
in winter, as happened most recently in the winter of
Since the bay is an estuary, it has fresh water and brackish water.
Brackish water has three salinity zones — oligohaline,
mesohaline, and polyhaline
. The fresh water 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
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 Rapahannock
River. Salinity there ranges from 10.7 ppt to 18 ppt. 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 18.7 ppt to 36 ppt. (36 ppt is as salty as the
explorer Lucas Vásquez
de Ayllón sent an expedition out from Hispaniola in 1525, led by Captain Pedro de Quejo, which reached the mouth of
the Chesapeake and Delaware
Bays and may have been the first European expedition to explore parts of the
Chesapeake Bay. De Ayllón established a short-lived Spanish mission settlement, "San Miguel de Gualdape", in
1526 along the Atlantic coast. Many scholars doubt the assertion that it
was as far north as the Chesapeake; most place it in present-day
Captain John Smith of England explored and mapped the bay between 1607 and
1609. The "Captain John Smith Chesapeake National
Historic Trail", the United States' first-ever all-water National Historic Trail, was created
in July 2006.
The bill passed by voice vote in the House of
Representatives and by unanimous consent in the Senate.
Chesapeake Bay was the site of the Battle of the Chesapeake in 1781,
during which the French fleet
defeated the Royal Navy in the decisive
naval battle of the American
the Calvert Cliffs Nuclear Power
Plant uses water from the bay to cool its
The bay is also known for the Chesapeake Bay Retriever
developed in this area.
The largest rivers flowing directly into the bay, from north to
A charter fishing boat on the
The bay was once known for its great seafood production, especially
. The plentiful oyster harvests led to the
development of the skipjack, the
state boat of Maryland, which is the only remaining working boat
type in the United
States still under sail power.
bay area workboats include:
Today, the body of water is less productive than it used to be,
because of runoff
from urban areas
(mostly on the Western Shore
) and farms (especially on the
harvesting, and invasion of foreign
. The bay still yields more fish
(about 45,000 short tons
or 40,000 tonnes
any other estuary in the United States.
The bay is famous for its rockfish
known as striped bass
. Once on the
verge of extinction, rockfish have made a significant comeback due
to legislative action that put a moratorium on rockfishing, which
allowed the species to repopulate. Rockfish are now able to be
fished in strictly controlled and limited quantities.
Oyster farming is a growing industry for the bay to help maintain
the bay's productivity as well as a natural effort for filtering
impurities in the bay in an effort to reduce the disastrous effects
of man-made pollution
In 2005, local governments began debate on the introduction to
certain parts of the bay of a species of Asian oyster
, to revive the lagging shellfish
Deteriorating environmental conditions
In the 1970s, the Chesapeake Bay was discovered to contain one of
the planet's first identified marine
, where hypoxic
waters were so depleted of
oxygen they were unable to support life, resulting in massive fish
kills. Today the bay's dead zones are estimated to kill 75,000 tons
of bottom-dwelling clams and worms each year, weakening the base of
the estuary's food chain
and robbing the
blue crab in particular of a primary food source. Crabs themselves
are sometimes observed to amass on shore to escape pockets of
oxygen-poor water, a behavior known as a "crab jubilee". Hypoxia
results in part from large algal blooms
which are nourished by the runoff of farm and industrial waste
throughout the watershed. This algae
prevents sunlight from reaching the bottom of the bay while alive
and deoxygenates the bay's water when it dies and rots. The erosion
and runoff of sediment
into the bay,
exacerbated by devegetation, construction and the prevalence of
pavement in urban and suburban areas, also blocks vital sunlight.
The resulting loss of aquatic
has depleted the habitat for much of the bay's
animal life. Beds of eelgrass
, the dominant
variety in the southern bay, have shrunk by more than half there
since the early 1970s. Overharvesting, pollution, sedimentation and
disease has turned much of the bay's bottom into a muddy
One particularly harmful algae is Pfiesteria piscicida
, which can
affect both fish and humans.
Depletion of oysters
While the bay's salinity is ideal for oysters, and the oyster
fishery was at one time the bay's most commercially viable, the
population has in the last fifty years been devastated. Maryland
once had roughly 200,000 acres of oyster reefs. Today it has about
36,000. It has been estimated that in pre-colonial times, oysters
could filter the entirety of the Bay in about 3.3 days; by 1988
this time had increased to 325 days. The harvest's gross value
decreased 88% from 1982 to 2007.
The primary problem is overharvesting. Lax government regulations
allow anyone with a license to remove oysters from state-owned
beds, and although limits are set they are not strongly enforced.
The overharvesting of oysters has made it difficult for them to
reproduce, which requires close proximity to one another. A second
cause for the oyster depletion is that the drastic increase in
human population caused a sharp increase in pollution flowing into
The bay's oyster industry has also suffered from two diseases:
Oyster recovery attempts
The depletion of oysters due to overharvesting and damaged habitat
has had a particularly harmful effect on the quality of the bay.
Oysters serve as natural water filters, and their decline has
further reduced the water quality of the bay. Water that was once
clear for meters is now so turbid
wader may lose sight of his feet before his knees are wet.
Efforts of federal, state and local governments, working in
partnership through the Chesapeake Bay Program
, and the
Chesapeake Bay Foundation
and other nonprofit environmental groups, to restore or at least
maintain the current water quality
have had mixed results. One particular obstacle to cleaning up the
bay is that much of the polluting substances arise far upstream in
lying within states far
removed from the bay itself. Despite the state of Maryland spending
over $100 million to restore the bay, conditions have continued to
grow worse. Twenty years ago, the bay supported over six thousand
oystermen. There are now fewer than 500.
Efforts to repopulate the bay with via hatcheries have been carried
out by a group called the Oyster Recovery Partnership, with some
success. They recently placed 6 million oysters on eight acres of
the Trent Hall sanctuary. Scientists from the Virginia
Institute of Marine Science at the College of William & Mary claim that experimental reefs created in 2004 now
house 180 million native oysters, Crassostrea virginica, which is far
less than the billions that once existed.
The Chesapeake Bay is a main feature for tourists who visit
Maryland and Virginia each year. Fishing, crabbing, swimming,
boating and sailing are extremely popular activities enjoyed on the
waters of the Chesapeake Bay. As a result, tourism has a notable
impact on Maryland's economy.
- Also shown as "Chisupioc" (by John
Smith) and "Chisapeack", in Algonquian "Che" means "big" or
"great", "sepi" means river, and the "oc" or "ok" ending indicated
something (a village, in this case) "at" that feature. "Sepi" is
also found in another placename of Algonquian origin, Mississippi. The
name was soon transfered by the English from the big river at that
site to the big bay.
- Other sources give values of 25 feet (e.g. ) or 30 feet deep (
- Oysters: Gem of the Ocean, The Economist,
December 8, 2008; accessed September 2, 2009.
- Program turns pork into oysters, Jesse Yeatman,
South Maryland Newspapers Online, August 12, 2009.
- Oysters Are on the Rebound in the Chesapeake Bay,
Henry Fountain, The New York Times, August 3, 2009; accessed
September 8, 2009.
- Cleaves, E.T. et al. (2006). Quaternary geologic map of the
Chesapeake Bay 4º x 6º quadrangle, United States
[Miscellaneous Investigations Series; Map I-1420 (NJ-18)]. Reston,
VA: U.S. Department of the Interior, U.S. Geological Survey.
- Phillips, S.W., ed. (2007). Synthesis of U.S.
Geological Survey science for the Chesapeake Bay ecosystem and
implications for environmental management [U.S. Geological
Survey Circular 1316]. Reston, VA: U.S. Department of the Interior,
U.S. Geological Survey.
Bay Area Publications