Overview: I have decided to add an unplanned segment to the Politics and the Chesapeake Bay series. I felt there were sufficient questions following the first article in the series (Pt 1) to warrant an intermediary article to answer those questions. The two big areas of interest involved the uniqueness of the Chesapeake Bay (especially as an estuary) and the forces continuing to change the bay (especially rising sea levels).
What is an estuary? It is a partly enclosed body of water with one or more rivers or streams flowing into it. Some definitions add a requirement for brackish water. The bottom line is that there is no completely accepted definition of an estuary. However, like pornography, you know it when you see it. The Chesapeake Bay is unquestionably an estuary. So are both the San Francisco Bay and the St Lawrence River. Other bodies of water, like the Gulf of Mexico, might meet the technical definition of an estuary but wouldn’t qualify in my book.
Is the Chesapeake Bay unique? In many ways, yes. The Chesapeake Bay is not the largest estuary in the world. That distinction belongs to the Rio de la Plata located between Argentina and Uruguay. However, the Chesapeake is the largest estuary in the United States and is generally considered the third largest estuary in the world. Yet even these “facts” can be disputed. By surface area, the largest estuary is Rio de la Plata. By length it is the St Lawrence River. By miles of shoreline it is the Chesapeake Bay. By any measure, the Chesapeake joins a very few other aquatic marvels (such as Florida’s Everglades) as one of America’s most important natural wonders.
The Changing Chesapeake. Anybody who boats on the middle section of the Chesapeake Bay knows Sharp’s Island Lighthouse (pictured in this post). The lighthouse sits at the intersection of the Choptank River and the main bay. It is instantly recognizable by its 20 degree tilt (caused by ice floes during particularly cold winters). The current Sharp’s Island Lighthouse was not the first. The first lighthouse was built in 1837 on top of a 900 acre island which was home to a thriving agricultural community. Named Sharp’s Island after the Quaker physician who once owned it, the island was a beautiful place in the mid 1800s. So beautiful that a wealthy Baltimore shoe manufacturer built a resort hotel on the island. There was only one problem – the island was rapidly sinking into the Chesapeake Bay. The isle (which measured 900 acres in the 17th century) was down to 94 acres by 1900. The island is under 9 to 12 feet of water today.
The rising tide. The water level in the Chesapeake Bay’ along with the rest of the Mid-Atlantic coast’ is rising at twice the rate of sea levels worldwide. This amounts to 1.3 feet per century at the mouth and 1.0 foot per century in mid-bay. That’s a lot of extra water but far from enough to put a hotel that was dry in 1900 under ten feet of water today. The Chesapeake Bay has been identified as one of four anomalous areas along the U.S. East Coast that appear tectonically active. There is a down-warping of the Earth’s crust called the Salisbury embayment. This embayment could certainly be the root cause of the mini-Atlantis known as Sharp’s Island. However, the entire US Mid-Atlantic coast is experiencing sea level increases well beyond global averages. And the Salisbury embayment cannot be blamed for all of that!
