Clams marked the typical Atlantic shoreline, their abandoned shells highlighting its edge like a beach necklace.

Our family parked by the typical Atlantic shoreline, our camper one among many, yet another bulbous clamshell fringing a coastline.

Clams and trailers trace the water’s edge, a proxy for sea level. The shoreline is their habitat, the place where ocean meets land meets air, a niche just right for filterfeeding, and for the sunsets and scuba and sandbathing, that clam and recreational lives thrive on.

Our trailer trail twisted beside the tides, a fiberglass dune paralleling sands and marsh grasses wading to their knees in the slops of seawater and swamp. We spent several trailer summers on Chincoteague Island in Virginia in the 1970s. Chincoteague is famous for its ponies, but we came for the clams.

We took a boat over to quiet, fly-infested wetlands sprouting Spartina in scarcely settled silt that sucked our shoes like quicksand. Awash rolling in, adry rolling out, tide-rinsed Spartina cordgrasses amplified the boundary between wet and dry at mudflats in the marshy muck that measured the meeting of marine and meteorological.

We raked the sediments for tunneling rocks, chasing them down as clams, catching some big beauties. We also gathered whelks, giant snails sitting submerged on the settlings, fellow clam-eaters vying with us for the monster mollusks. Mom cooked them all up in chowder.

They weren’t enough for Dad.

Dad bought 50 pounds of cherrystone clams, in a huge mesh bag that nearly knocked him over when he tossed it over one shoulder. He said they were mostly shell and he could suck them down in a couple of hours.

But 50 pounds is a lot of clams. He was slurping them raw, slathered with cocktail sauce, which looked both snotty and gory. Mom would have nothing to do with them.

“Try one!” he offered, adding, “Shut your eyes; it’ll taste better.”

I shut my eyes. Suddenly, I was crunching on a gritty, slimy eyeball of horseradish seawater. It was awful.

I must have tasted it wrong, because Dad was really appreciating them, so I tried another, but en route I opened one eye to take a peek, and there, regal on a pillow of clam mantle, glowed the cherrystone ... No, it was a pearl! It was not as iridescent as those on Mom’s necklace, and it was shaped like a sandbag, but, Mom, it was a pearl, a clam pearl.

Irritated clams grow pearls, and life in the tidal zone is a constant irritation. Clams are specialists that live among the dry and wet, warm and cold, fresh and salty, as the tides and waves jostle in and out, submerging and emerging, in a range of existence that would exhaust other species. But this is their cherrystone jam. Of all the habitats and all the creatures, these abodes abide.

For hundreds of millions of years, creatures large and small, through spring and fall, beneath blaze and squall, have staked out the intertidal zone despite its hardship, because no one else wants to live there. They live and die, literally, in the littoral. And when a clam dies, its shell remains behind, in a grave covered by waves and, occasionally, transformed to a fossil.

The fossil permanently marks the shoreline, and as generations live and die, and as the shoreline ebbs and flows, comes and goes, the shells mark where it has been.

So researchers dig down looking for pearls of clam history, and with it the shoreline’s history. Here lies the watermark, the indelible trace, that tracks the inland and outland extent of the rising and falling ocean throughout history.

And they find that through Earth’s deep history, that height has changed, falling during ice ages when would-be ocean water is frozen onto land, then rising when the ices melt, a 10,000-year surge and slack.

In Virginia and North Carolina, we also see the recoil effects of glaciers. Icy mountains piled onto Canada 25,000 years ago, weighing it down into the deeper layers of Earth. The stiff crust of North America beyond the ice levered upward as a result. Over the last 15,000 years, the ice has been retreating, and as the ice-weight melts back into the sea, the ocean level fills, and the up-levered land of North America settles back down. The downward seesaw, slowly dipping our coast into the waves, has been augmented by the addition of the meltwater and swelling of the warming water. In the last 200 years, the meltwater and swellwater effects have compounded the seesaw effect, and the waterline has moved upward, and inland, by about a foot of melt and a foot of seesaw.

So as the climate changes, there is a sea level to chase, a scalloped edge of clams and jams that transgresses and regresses, and science will examine the chronicle of the clam community to foretell the tomorrow trail of trailers.

Some of those scientists have written a book about their research adventures in North Carolina and around the world, and some of them are from East Carolina University. The new book is Troubled Waters: Understanding the Science Behind our Coastal Crisis, edited by ECU Geology chairman Steve Culver (Springer, 2021).

Joy Moses-Hall teaches physics and astronomy at Pitt Community College. She has a PhD in oceanography and is the author of the novel Wretched Refuge. Follow her @jmoseshall on Facebook.