Chesapeake Bay

• 1. A Drowned Valley From The Sky

  ›

  The Chesapeake Bay stretches 180 miles from the Susquehanna River to the Atlantic Ocean, yet its true origin lies buried beneath the water. A massive asteroid struck the region approximately 35.5 million years ago during the Eocene epoch. This impact created a crater that shaped the geological foundation of the entire estuary. Rising sea levels at the end of the last ice age flooded the river valley about 10,000 years ago. The resulting body of water became the largest estuary in the United States. It sits between the Delmarva Peninsula and the North American mainland. The bay spans from Maryland down into Virginia. Its average depth is just over 30 feet, though some areas reach depths exceeding 200 feet. The shoreline extends for more than 6,400 miles when including all tributaries. Scientists study the Calvert Cliffs along the western shore where fossilized shark teeth wash up on beaches. These cliffs contain deposits from receding waters millions of years old. The community of Scientists Cliffs was founded in 1935 as a retreat for researchers studying these ancient layers.

• 2. Villages On The Water Edge

  ›

  Paleoindians inhabited the area around 11,000 years ago before European contact. Native American societies lived in villages of wooden longhouses close to water bodies. They fished and farmed the land using agricultural products like beans, corn, tobacco, and squash. Villages often lasted between 10 and 20 years before being abandoned due to resource depletion. Men hunted while women supervised farming operations within these communities. All village members participated in harvesting fish and shellfish from local bodies of water. Communities formed confederations such as the Powhatan, Piscataway, and Nanticoke. Each confederation consisted of smaller tribes under the leadership of a central chief. The name Chesapeake comes from an Algonquian word meaning at a big river. Explorers first applied the name Chesepiook in 1585 or 1586 when heading north from Roanoke Colony. The Spanish called it Bahia de Santa Maria during their early expeditions. John Smith published A Map of Virginia in 1612 after exploring the bay between 1607 and 1609. He wrote that heaven and earth never agreed better to frame a place for man's habitation.

• 3. Naval Battles And Colonial Maps

  ›

  Italian explorer Giovanni da Verrazzano sailed past the Chesapeake Bay in 1524 without entering it. Spanish explorer Lucas Vásquez de Ayllón sent an expedition out from Hispaniola in 1525 that reached the mouths of the bay. They established San Miguel de Gualdape along the Atlantic coast in 1526. Pedro Menéndez de Márquez conducted further exploration of the Chesapeake in 1573. English colonists arrived under Sir Walter Raleigh and Humphrey Gilbert in the late 16th century. Three decades later, Europeans entered the bay again through Cape Charles and Cape Henry. Captain John Smith explored and mapped the region resulting in his 1612 publication. Mass migration of southern English Cavaliers occurred between 1640 and 1675 to both Virginia and Maryland colonies. The Battle of the Chesapeake took place in 1781 during the American Revolutionary War. The French fleet defeated the Royal Navy in this decisive naval engagement. General George Washington marched down from New York with French allies under Comte de Rochambeau. Their route went from Newport Rhode Island through Connecticut and Pennsylvania to the Head of Elk by the Susquehanna River. British forces raided towns on the shores of the bay during the War of 1812. Admiral George Cockburn treated the bay as if it were a British Lake from their base on Tangier Island.

• 4. Sharks And Shellfish In Brackish Water

  ›

  Over 300 species of fish inhabit the Chesapeake Bay along with numerous shellfish and crab species. Atlantic menhaden, striped bass, American eel, eastern oyster, and Atlantic horseshoe crab live here year-round or migrate seasonally. Birds include ospreys, great blue herons, bald eagles, and peregrine falcons whose numbers rose after DDT threats subsided. Bottlenose dolphins live seasonally or yearly within the bay waters. A male manatee nicknamed Chessie visited between 1994 and 2011 despite being north of its normal range. Loggerhead turtles are known to visit the bay regularly. Submerged aquatic vegetation includes eelgrass and widgeon grass which provide food and habitat for many species. Dense stands of Brazilian waterweed have spread to most continents and can restrict water movement. Phragmites and Purple loosestrife have established high levels of permanency in Chesapeake wetlands. The bay has three salinity zones ranging from fresh to saltwater conditions. The oligohaline zone runs from north Baltimore to the Chesapeake Bay Bridge where freshwater species survive. The mesohaline zone extends from the bridge to the Rappahannock River mouth with medium salt content. The polyhaline zone reaches from the river mouth to the ocean with salinity up to 3.6 percent.

• 5. The Collapse Of Oyster Reefs

  ›

  Maryland once had roughly 115,000 acres of oyster reefs before modern decline. In 2008 there were about 1,700 acres remaining after decades of overharvesting. The harvest gross value decreased 88 percent from 1982 to 2007. One report suggested the bay had fewer oysters in 2008 than 25 years earlier. Lax government regulations allowed anyone with a license to remove oysters from state-owned beds. Limits were set but not strongly enforced making reproduction difficult for the species. A second cause for depletion was the sharp increase in pollution flowing into the bay due to human population growth. Two diseases named MSX and Dermo devastated the industry further. Oysters served as natural water filters so their decline reduced overall water quality. Water that was once clear for meters is now so turbid that waders lose sight of feet while knees remain dry. Maryland supported over 6,000 oystermen in the mid-20th century. As of 2008 fewer than 500 remained working full-time. Skipjacks like the Helen Virginia became the only remaining working boat type still under sail power in the United States. Other characteristic workboats include log canoes, pungys, bugeyes, and motorized deadrise vessels.

• 6. Dead Zones And Nutrient Runoff

  ›

  The Chesapeake Bay contained one of the planet's first identified marine dead zones by the 1970s. Waters depleted of oxygen resulted in massive fish kills unable to support life. In 2010 estimated dead zones killed 75,000 tons of bottom-dwelling clams and worms each year. Crabs sometimes amassed on shore to escape pockets of oxygen-poor water known as crab jubilees. Large algal blooms nourished by residential farm and industrial waste throughout the watershed caused hypoxia. A 2010 report criticized Amish farmers in Pennsylvania for raising cows with inadequate manure controls. Farms in Lancaster County generated large quantities of manure washing into tributaries. About half of nutrient pollutant loads came from manure and poultry litter. Extensive use of lawn fertilizers and air pollution from vehicles were also significant sources. The sediment record shows a major increase in nutrient levels starting between the 17th and 18th centuries. Recently deposited sediments contain 4 to 20 times greater amounts of nitrogen and phosphorus than pre-colonial eras. Algae take up nutrients and rapidly reproduce in blooms before sinking to decompose and consume oxygen. Seasonal stratification typically occurs between spring and early fall creating strong pycnoclines about 10 meters below surface. Dissolved oxygen levels reach near zero by mid-June and persist until October.

• 7. Agreements And Legal Battles

  ›

  Congress directed the Environmental Protection Agency to study scientific aspects beginning in the late 1970s. The agency published a major report in 1983 stating the bay was an ecosystem in decline. Maryland and Virginia legislatures established the Chesapeake Bay Commission as an advisory body in 1980. Partners developed the Chesapeake Bay Agreement signed in 1983 by governors and the EPA Administrator. An Executive Council consisting of cabinet-level appointees coordinated technical issues for restoration. The program office based in Annapolis is partially funded by EPA and staffed by experts from member states. In 1987 parties agreed to reduce entering nutrients by 40 percent by 2000. The Chesapeake Bay Foundation filed suit against EPA in 2009 for failure to finalize total maximum daily load rulings. EPA issued its TMDL document on the 29th of December 2010 requiring all watershed states to develop implementation plans. CBF filed another lawsuit in 2020 regarding New York and Pennsylvania compliance reaching settlement in 2023. Governor Wes Moore signed the Chesapeake Bay Legacy Act in May 2025 allotting up to $900,000 annually for farmer certification programs. The state intends to initiate all necessary pollution reduction actions by 2025. Restoration efforts began in the 1990s showing potential for native oyster population growth.

• 8. Rising Seas And Future Threats

  ›

  Water levels in the bay have already risen one foot since measurements began. Predictions indicate an increase of 1.3 to 5.2 feet over the next 100 years due to climate change. Sea level rise causes changes in marine ecosystems destruction of coastal marshes and wetlands. Saltwater intrudes into otherwise brackish parts of the bay threatening freshwater habitats. Islands such as Holland Island have disappeared entirely from rising sea levels. The 11,600 miles of coastline including historic buildings face erosion risks from flooding events. Warmer waters hold less dissolved oxygen extending hypoxia duration each summer season. Ocean acidification makes it harder for shellfish to maintain shells against increasing pressure. Seasonal shifts mean greater likelihood of pathogens staying active in the ecosystem. Key infrastructure like the port of Norfolk faces direct impact from changing conditions. Major agriculture and fishing industries on Maryland Eastern Shore will be directly affected. Projected effects include decreasing dissolved oxygen more acidic waters and altered breeding cycles. Compared to current nutrient pollution effects climate change increases are relatively small but compounding. Scientists monitor temperature salinity chlorophyll concentration and turbidity through continuous programs. Organizations including NOAA Chesapeake Bay Office and Virginia Institute of Marine Science collect data regularly.