Contours of Chesapeake Bay Coastline, USA – May 30th, 200937.5N 76.1W
The Chesapeake Bay (middle) is the largest estuary in the United States. It lies off the Atlantic Ocean, surrounded by Maryland (above) and Virginia (below). Parts of the states of Delaware and New Jersey are also visible in the upper right quadrant. Also of note is a plume of smoke at the lower left, from a fire in Virginia.
The Chesapeake Bay stretches about 200 miles (300 km) from the Susquehanna River in the north to the Atlantic Ocean in the south. 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.
Much of the bay is quite shallow. At the point where the Susquehanna River flows into the bay, the average depth is 30 feet (9 m), although this soon diminishes to an average of 10 feet (3 m) from the city of Havre de Grace for about 35 miles (56 km), to just north of Annapolis.
In this image, sun glint makes the water of the bay appear whitish, and thus highlights the contours of the coastline. However, despite the glint it is still possible to observe some greenish sediments flowing into the bay.
Since the bay is an estuary, it has fresh water and brackish water. Brackish water has three salinity zones — oligohaline (little salt, freshwater species able to survive), mesohaline (medium amount of salt), and polyhaline (very salty, sometimes as much as sea water).
In the Chesapeake Bay, the fresh water zone runs from the mouth of the Susquehanna River to north Baltimore. The mesohaline zone reaches from the Bay Bridge to the mouth of the Rapahannock River, and the salty polyhaline zone runs from the mouth of the Rappahannock River to the mouth of the bay.