Nature Notes: Does It All Become Dust?

   The e-news just reported that sea level is rising on America’s East Coast faster than on the West Coast. What this translates into is the retreat of beaches and bluffs, the flooding of tidal wetlands, and the salting of drinking water wells situated close to the sea. On the other hand, while there will be losses and changes, there will also be more of the same.

    Each shoreline on the South Fork of Long Island is different. Some are backed by coastal bluffs such as those in Montauk, some are fronted by dunes like those in Amagansett, some are edged with salt marshes, some are stony, some are sandy, and some, such as the points and strands, are flat, low, and barren.

    Middle Atlantic Coast beaches are different from Gulf of Mexico beaches. They have two flood tides and two ebb tides in a 24-hour day as opposed to one high and one low in the same time period. The tides washing in and out with accompanying waves are responsible in large part for a given beach’s profile and character.

    The ocean beaches of the south shore are mostly sandy. On Long Island, one has to travel all the way to Montauk to find stony ocean beaches. Traveling east from Napeague they become progressively stonier and the bluffs behind them progressively steeper.

    Why is that? Well, the ice sheet that created the South Fork about 15,000 years ago reached no farther south than the morainal highlands that run east-west in a line dividing the northern half of Southampton and East Hampton Towns from their southern halves. Montauk is an exception, however, as the glacier dropped and pushed its load of rocks and other debris far out into the ocean.

    Thus Montauk’s south shore and subtidal waters are mostly lined with rocks known as glacial erratics. Striped bass fishermen stand on the tops of the larger ones in the water while they fish. Boulders brought 15 millenniiums earlier from New England and Canada continually wash out of the bluffs, roll onto the beach, and in less than 100 years are partly underwater or completely so as rising sea level claims more and more of the retreating shore. The really big ones move hardly an inch or more over time while the sea overruns them. The biggest ones are shown on hydrological charts created by the Department of the Interior and they serve as important navigation points for boaters.

    The north shore beaches lining the Peconic Estuary, a series of bays beginning on the west where the Peconic River runs into the estuary and endng on the east with Block Island Sound are quite different from the ocean beaches. They are much stonier and have a lot more shells, different ones that you find on ocean beaches. The tides and storms drive the larger materials back and forth in a never-ending process called “sorting” by geologists. The sediments are sorted according to size and weight. Sand is lighter than gravel and gravel is lighter than stones and stones are lighter than rocks and so on. There are glacial erractics, as well, here and there along north shore shorelines. Drive over the Route 114 bridge from the Village of Sag Harbor into the Village of North Haven and look to the northeast at ebb tide. Sag Harbor Bay’s northwest side is littered with glacial erratics. They haven’t moved an inch in ages.

    Continue on to Long Beach Road around the corner of Route 114 and you will find perhaps the best hydraulically sorted beach on the South Fork, situated between Noyac Bay and Sag Harbor Cove. On any given day, there are at least four different zones running the length of the beach from North Haven into Noyac. At the top is fine sand and some dried seaweed left by storm and moon tides. A little farther down is a layer of empty slipper shells and jingle shells, purplish and yellow. Gravel also makes up this layer, lying beneath the shells because of its greater density. Then comes a layer of finely polished stones, mostly white quartz, followed by a layer of larger stones, or rocks, also well polished but much heavier than the stones in the more landward layer.

    You will also find another mode of transportation from sea to shore ongoing among these larger rocks. Rockweeds, Sputnik weed, and other algae attached by their holdfasts to rocks that are among the largest and most seaward. The buoyancy of the attached seaweed makes these rocks a little lighter and more mobile than those without seaweed and so they move closer to shore with each large wave. One gets the notion that the seabed is continually purging itself of rocky sediments.

    The north side of Orient Point, Fishers Island, Gull Island, and Plum Island — all formed by the glacier that created the Harbor Hill moraine that runs along the north shore of Long Island out into the ocean — also have stony beaches that show a similar horizontal zonation from seabed to upper shore to that on Long Beach.

    Some South Fork shores show a zonation of sands. White quartz sands are the most common, while garnet sands often form red wrack lines high up on the beach along with iron, or magnetite sands, which are blackish. One responds to a horseshoe magnet, the other doesn’t. Such differential sanding is common along Napeague Harbor’s shoreline, but also occurs on all the shores and points of the Peconics, as well as on some upper ocean beaches.

    While Lion’s Head Rock and the other massive boulders will likely last until the end of earth as we know it, semidiurnal tides and storm-driven seas are eternally grinding and grinding silicate against silicate against silicate, rock against stone against gravel against sand grains along our marine shores in a different kind of “food chain,” one that creates smaller and smaller particles from larger ones.

    What is the end point? That’s what I would most like to know. After the wind takes over, do the finer and finer sands eventually become atmospheric dust, which ultimately reduces to single and separate molecules, maybe even individual atoms? Think about it.

    One need not fret over it, however. The earth is not shrinking; it is growing larger. It loses far less material to space than it receives from it in the form of asteroids, meteors, and meteorites. The earth is slowly becoming obese.