Places and Values Revisited

Bethany Beach in Delaware will always have a special place in my heart, and the work we have done this semester has helped deepen my connection to the environment. There are two parts of Bethany, one part that is connected to the mainland and a part that jets out between the ocean and a really large, marshy bay. I think that Bethany, and the surrounding towns of Dewey and Fenwick Island, fits the definition of a barrier island, and if you look at the area as such, it allows us to ask a lot of questions about the past and future of the area.

I decided to first look up a geologic map of Delaware, and this map looked a lot different than the bedrock maps I have seen before — I’ve only seen New York and Massachusetts. The map seemed to indicate that there was a very old and eroded mountain range (the Piedmont formation) at the northernmost part of the state, near Pennsylvania. I think this mountain range is the source of the sediment that Bethany, and the larger Atlantic Coastal Plain, lies on. This sediment would have been transported to Bethany from the mountains by rivers and gravity. Therefore, the golden beaches I discussed at the beginning of the semester are probably bits of quartz and feldspar from the eroded mountains. If I was there now, I would try and see how well sorted the sand was. I would expect the sand to be pretty well sorted: all pieces would be about the same size and fairly rounded because of all the weathering it would have undergone as it traveled here via rivers and streams.

Next I thought a lot more about the barrier island part of Bethany. A barrier island is a strip of land between a bay/tidal marsh and an ocean. The tidal marsh is filled with super dark mud because of all of the carbon from organic matter, like plants and animals, and the bay fills and drains with the ocean tides. Barrier islands are characterized by migration and constant movement. Through wash-over events from large storms, like Hurricane Sandy and Hurricane Irene, sand from the front of the barrier island, the beach, is eroded and redeposited to the bay-side side of the island in wash-over fans. I am pretty sure that at least part of Bethany is a barrier island, or it once was a barrier island that is now attached to the mainland by a very thin strip of sand (about the width of a road). My family’s house in Bethany faces the bay, so I have firsthand seen the dark and smelly mud that lies at the bottom of the bay. We go crabbing and fishing in the bay, which is surrounded by grassy plants, so that would explain all of the organic matter in the mud. After these organisms die and become part of the mud, the mud is buried by the migrating island and it becomes peat, so I could test my theory about Bethany being a barrier island by digging deep into the soil on the sea-ward side of Bethany and seeing if I find peat from the bay or even looking for old tree roots.

I also think that Bethany is a barrier island, or at least part of it is, because of how unstable the beach is. Like all beaches, Bethany loses a lot of sand in the winter and gains it back in the summer, and when there are really big storms, the beach changes drastically. Specifically, there is one part of Bethany which is less than a quarter of a mile thick between the bay and the ocean, and it stays this thickness for five miles. In other words, it’s a super thin piece of land that goes on for a while between the bay and the ocean. There is a road that runs down this strip of land, and there are sand dunes directly to the right of road, on the seaward side. Whenever there is a storm, the dunes spill into the road itself, and the dunes are super fragile (there are countless projects where they try to plant grasses to keep the dunes in place). I think this supports my theory that it’s a barrier island, and I think that the road probably lies on a washover fan, and the land is trying to migrate toward the bay. Furthermore, I think it is interesting that even though this land is super sandy (because it’s a beach), the geologic map says the land is underlain by swampy/muddy deposits, so this could be another example of barrier island migration. A question this raises in my mind is how fast is the land moving; to answer this, maybe you could date the mud/peat or look for things like old tree roots on the beach to find the rate of movement.

There is also a break in the thin piece of land where there is a large bridge, which is coincidentally right next to my favorite beach spot. It is under this bridge that a lot of boats travel; the little break is important for recreation, so the town artificially keeps it open with a really big jetty, which makes the sand pile up to make my beach. I think that this break in the strip of land was originally formed in a dune breeching event during a storm. So, if I am correct, the two pieces of long, thin land were once a long, continuous piece between two land masses attached to the mainland. I don’t know how I would test this hypothesis; maybe I could look for historical accounts because the coastline is a landscape that changes on relatively short timescales.

The awareness of the movement of barriers and their fleeting nature makes me sad to be honest because I wonder how long Bethany will look the way it does. Bethany is where I made some of the happiest moments in my childhood, and I want my kids to experience what I did, and their kids and their kids. The coastline is dynamic, and it is obvious that the town is trying to fight that change through replenishing sand at the beginning of spring and building levees. I wonder if my favorite beach, on that narrow strip of land, will still be there in 100 years, or if it will be further in toward the bay. Will the pretty houses that my sister and I called “dibs” on when we were little be underwater because of the migration of the land? But I remember that these processes are inevitable, and combating them can only backfire. For example, Rehoboth beach a few miles north of Bethany has a lot of jetties every hundred feet that obstruct swimming and look really ugly, forming mini diagonal beaches. I also have started to think about how littering and emissions from boats in the bay affect the formation of peat; if they don’t degrade, the plastics that we release into the bay could theoretically make its way onto the other side of the barrier island as washover occurs, and maybe even into the ocean, which would affect larger ocean systems like ocean gyres. If I get the chance to go to Bethany this summer and visit my house on the bay, I will think about how, if the strip of land keeps migrating, my house could be underwater one day (washover could keep occurring until the bay is ocean). I also have been wondering if washover events are happening more often, and the landscape is changing more rapidly and more drastically, because of climate change. Therefore, I fear we are speeding up the natural geologic process; we’re letting the beach suffer. These are questions I wouldn’t be able to even ask, let alone answer, without the work we have done this semester.

 

Lizzy Birmingham

Professor Jones

Surface Earth Dynamics

May 13, 2020