chesapeake bay

The Chesapeake Bay is the largest estuary in the United States. It lies off the Atlantic Ocean, surrounded by Virginia and Maryland. The Chesapeake Bay's watershed covers 64,299 mi² (166 534 km²) in the District of Columbia and parts of five states: New York, Pennsylvania, Delaware, Maryland, Virginia,. More than 150 rivers and streams drain into the Bay.

The main stem of the Bay itself is 189 miles (304 km) long, from the Susquehanna River in the north to the Atlantic Ocean in the south. At its narrowest point near Annapolis, Maryland, the Bay is 4 miles (6.4 km) wide; at its widest point, near the mouth of the Potomac River, it is 30 miles (50 km) wide. Total shoreline for the Bay is 11,684 miles (18 804 km), and the surface area of the bay and its major tributaries is 4,479 mi² (11 600 km²).

The narrowest point of the Bay is spanned by the Chesapeake Bay Bridge. The Chesapeake Bay Bridge-Tunnel spans a 17 mile (27 km) section of the bay near its mouth.

Geology

The Bay is the ria, or drowned valley, of the Susquehanna, meaning that was where the river flowed when 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. Rather, the Bay's geology and its present form and its very location have also been affected by a bolide impact event at the end of the Eocene (about 35.5 million years ago), forming the Chesapeake Bay impact crater.

Parts of the bay, especially the big parts by the coastline of Calvert County, are lined by cliffs as the result of receding waters millions of years ago. These cliffs, generally known as Calvert Cliffs, are famous for their fossils, especially fossilized shark teeth. Fossilized shark teeth are commonly found washed up on the beaches next to the cliffs. Scientist's Cliffs is a beach community in Calvert County, named so because of the cliffs' propensity for geological finds and numerous fossils.

Much of the bay is quite shallow. At the point where the Susquehanna River flows into the bay the average depth is 30', although this soon diminishes to an average of 10' from the city of Havre de Grace for about 35 miles, to just north of Annapolis. A person 6 feet 7 inches (2 m) tall could traverse some 700,000 acres (2 800 km²) of the bay without being entirely submerged. On average, the depth of the Bay is less than 30 feet or 9 meters.

The climate of the area surrounding the bay is primarily humid subtropical, with hot, very humid summers and mild, rainy 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.

Since the bay is an estuary it has fresh water and brackish water. Brackish water has 3 salinity zones, oligohaline, mesohaline, and polyhaline. The salinity is measured on parts per thousands (ppt). The fresh water zone runs from the mouth of the Susquehanna River to north Baltimore. The oligohaline zone has very little salt. salinity veries from 0.5ppt-10ppt 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. the salinity ranges from 10.7ppt-18ppt. 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 Rapahannack River to the mouth of the bay. The salinity ranges from 18.7ppt-36ppt. 36ppt is as salty as the ocean.

History

The Chesapeake Bay was first explored and mapped by Captain John Smith during his explorations between 1607 and 1609. As of July 2006, two bills are circulating in the U.S. Congress to establish a Captain John Smith Chesapeake National Historic Trail.

The 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 Revolutionary War.

Today, the Calvert Cliffs Nuclear Power Plant uses water from the bay to cool its reactor.

The bay is also known for the Chesapeake Bay Retriever, a dog breed developed in this area.

Watershed

The largest rivers flowing into the Bay, from north to south, are:

• Susquehanna River
• Patapsco River
• Choptank River
• Patuxent River
• Potomac River
• Rappahannock River
• York River
• James River

Fishing Industry

The word Chesepiooc is an Algonquian word meaning "Great Shellfish Bay." The bay was once known for its great seafood production, especially blue crabs, clams and oysters. 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. 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 eastern shore), overharvesting, and invasion of foreign species. The bay though, still yields more fish and shellfish (about 45,000 short tons or 40 000 tonnes yearly) than any other estuary in the United States.

The bay is famous for its rockfish, also known as striped bass. Once on the verge of extinction, rockfish have made a significant comeback and are now able to be fished in strictly controlled and limited quantities.

The bay serves as the predominate source of eel in the United States.

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 industry.

Deteriorating environmental conditions

In the 1970s, the Chesapeake Bay contained one of the planet's first identified marine dead zones, where hypoxic waters were so depleted in oxygen they were unable to support life, resulting in massive fish kills. Large algae blooms, nourished by the runoff of farm and industrial waste throughout the watershed, prevent sunlight from reaching the bottom of the Bay. The resulting loss of marine vegetation has depleted the habitat for many of the Bay's animal creatures. One particularly harmful algae is Pfiesteria piscicida, which can affect both fish and humans. The depletion of oysters due to overharvesting and damaged habitat has had a particularly harmful effect on the quality of the bay. The bay's oyster industry has also suffered from two diseases: MSX and dermo. Oysters serve as natural water filters, and their decline has further reduced the water quality of the Bay. Water that was once clear for metres is now so turbid that a 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 tributaries lying within states far removed from the bay itself.

See also

• Delmarva Peninsula
• Dead zone (ecology)
• Chesapeake, a novel by author James A. Michener

External links

• RivahBiz.com - Chesapeake Bay Businesses
• Chesapeake Bay Program
• Chesapeake Bay Journal
• Chesapeake Bay Gateways Network
• Chesapeake Bay Foundation
• Alliance for the Chesapeake Bay
• Chesapeake Research Consortium
• Chesapeake Community Modeling Program
• Chesapeake Bay Bridge (near Annapolis, MD)
• Chesapeake Bay Bridge-Tunnel
• Maryland Sea Grant
• Scientist's Cliffs
• National Geographic- Saving The Chesapeake
• National Geographic- Exploring The Chesapeake Then and Now
• John Smith Water Trail Blog - Musings and Meanders on the Chesapeake Bay
• Captain John Smith Chesapeake National Historic Water Trail
• Sailing the Chesapeake Bay