Marconi Beach and the Myth of Accretion
I went out to Marconi Beach yesterday to see what it might have to say. At some times and places, where the bluffs are relatively low, say 30 or 40 feet, as they are here, and the tide fairly far out, as it was then, it’s the beach, in all its wide expanse, that takes precedence.
In other places, such as Truro’s Long Nook, where the cliffs are high, 150 feet or more, it’s the eroding face of the glacial scarp that commands attention. And in still other moments and settings, say when the bluffs are low, the beach narrow and constricted, and the tide high, it’s the ocean that holds sway.
That day it was the beach itself that held my attention, though there was not much on it but a few stark and broken forms of pitch pines, prostrate and wound with random ribbons of eelgrass. At the very edge of the lower berm, where saturated sand and random scatterings of multicolored stones provide a more solid footing, I found a rounded and flattened piece of puddingstone.
Puddingstone is a curious conglomerate, or cemented rock formation, consisting of distinct pebbles or rocks – sometimes even fairly large boulders, that were carried down mountainsides by melting glaciers into river valleys full of sand or other fine sediments. The massive weight of subsequent ice sheets fused together the rocks and sediment into formations that reminded English settlers of plum-pudding, hence the name puddingstone. The largest outcrops of puddingstone in our region can be found on the south side of the Blue Hills Reservation outside Boston.
Given its origin at the base of mountain rivers, it is unusual to find puddingstone on the Outer Beach. In fact, this is the first piece of puddingstone I have ever found on the beach. It was a particularly fine example, pleasingly oval-shaped, about 6 ½ inches long, 5 inches wide and nearly 2 inches thick. It was densely studded with raisin-sized pebbles of granite and other colorful minerals cemented together with hardened clay. It seemed to have the weight of time and compression in it, a geological Rosetta Stone, bespeaking ancient riverbeds of silt and stones, fused together by the cold weight of massive ice sheets, then ripped apart, perhaps by later glaciers, rolled and tumbled and at last thrown up here for my contemplation.
I put the stone in my backpack and passed a long stretch where beach grass, that ever-optimistic, ever-opportunistic plant, had apparently colonized the apron of the upper beach. It spread out some 20 to 25 feet from the base, though its bleached and bent blades were half-smothered in winter-blown sand.
A friend of mind had recently asserted that this stretch of beach had actually been “accreting,” or building up in recent years. I didn’t contradict him, though any long-term overview of the Outer Beach shows an essentially uniformly eroding or retreating edge. This should be enough to disabuse anyone of the illusion of “accretion.” Still, since the process is not uniformly linear, and in isolated segments the beach can at times seduce us into believing that the inevitable is not happening. It is the same illusion we have when, after some disability or illness or loss due to age, we experience, for a while, a sense of “recovery,” that we are somehow growing “younger” again. Well, stick a post in the sand on the beach and see if the earth builds up around it.