Alongshore

On the Beach

By Tamia Nelson
tamia@paddling.net

December 10, 2002

Now is the winter of our discontent. Well, Shakespeare wasn't a waterman, but come December, a lot of North American canoeists and kayakers begin to feel that way. Rivers that once sang over boulder-strewn beds now trickle between frozen banks, and pine-rimmed lakes lie newly sheathed in ice. Even the rocky New England coast is lashed by winter storms. It's not a happy time for paddlers.

There are remedies, of course. Some folks follow the sun south. Others strap on skis or snowshoes and make the most of the season of long shadows. Still others—perhaps most of us—settle down in front of the fire with a good book, to read and doze and dream. And what do we dream about? It's a safe bet that tropical beaches figure prominently. Who wouldn't prefer lazing on a palm-girt swathe of silver sand, swept by a gentle surf, to fighting white-knuckle battles in rush-hour traffic on some icy urban overpass? Not very many of us, I'm sure.

But not all beaches fit the bill. There's that rocky New England coast, for one. It can be a pretty formidable place even in high summer. And there's nary a palm in sight. So not every beach is a tropical paradise. In fact, there are almost as many types of beaches as there are varieties of paddlers. And this isn't something of interest only to geologists. Whether you're a sea kayaker, plan to buy a beachfront cottage, or just like to work on your tan, that's a good thing to bear in mind.

Let's begin at the beginning. What, exactly, is a beach? How about a gently sloping shore, washed by waves or tides? Sounds pretty good, as far as it goes, and it serves equally well for both fresh and salt water. (Lakes have waves, even if they don't have measurable tides.) But it's pretty general, isn't it? And as in most other things in life, it's the differences between beaches that make them interesting.

Describing such differences is much easier if we share a working vocabulary, obviously. So take a look at this cross-section of an idealized ocean beach:

Here, the beach is shaded green. It rests on bedrock (brown) and lies between a height of land and the sea (blue). The intertidal zone marks the limits of high and low tides.

And what is a beach made of? Rocks and rock fragments, mostly, from boulders all the way down to fine sand. But not always. Anything that water can move and waves can grind can find its way onto—and into—a beach. Look at any handful of beach sand with a pocket magnifier or dissecting scope and you'll probably see tiny shards of ground plastic and other trash. Sometimes you won't even need a magnifier. Engineer (and beachcomber) Willard Bascom once described a pocket beach near Fort Bragg, California, that consisted entirely of tin cans from a nearby ocean dump. Not a great place to take the kids for a picnic, perhaps, but still a beach.

A pocket beach, by the way, is just a beach contained between two rocky headlands and—in many if not all cases—backed by a sheer cliff-face. Winter storms often strip away all the sand from these pockets, leaving only cobbles (or tin cans) behind. And this illustrates a larger point. Beaches live on the edge. A beach isn't frozen in time. It's a happening place. Beaches grow as material is deposited, and shrink when it's stripped away. Change is the only constant. Beaches migrate up and down a coast. They get washed out to sea. Sometimes they even become stranded far from water. Only then do they settle down. Beachfront property owners take note! A beach is not forever.

Geologists like to compare the shoreline to a battlefield. (Few geologists have seen a battlefield, but the imagery is compelling nonetheless.) Miles back from any beach, exposed rock is attacked by wind, water, and ice. Bulldozers and plows tear up the soil. Then rain washes bits and pieces of the displaced landscape into nearby rivers, which later empty into lakes and seas. What started out as scenery ends up as sediment, ranging in size from cobbles to clays. Sooner or later this sediment settles out. Some is lost to the deeps, but the rest accumulates along the shifting shoreline. When this first occurs, a beach is born. And that's only the first chapter of the story. Waves constantly lay siege to the shore, plucking sand from existing beaches and washing it out to sea again, or smashing large stones into smaller fragments. Alongshore currents carry these freshly-liberated sediments to new locations. The result? One beach shrinks, while another grows.

The beach is dead. Long live the beach! The only thing constant is change.

Beaches are shaped by this never-ending struggle. Their character depends on the parent material that gave birth to the sediments that formed them. It also depends on the forces at work on those sediments. Tahiti has beaches of black volcanic sand, whereas the shore of Florida's Gulf coast boasts fine white "sugar," the remains of shattered coral reefs. The Labrador coast is studded with storm-washed cobbles, while beaches on the western margin of Lake Champlain contain the coarse-grained remnants of frost-cracked Adirondack rock. And Fort Bragg has tin cans.

That's just the beginning, of course.

Remember the hazy phrase gently sloping from the definition of a beach? Here's a slippery slope, indeed! What's gentle? What's steep? It depends. If a beach slopes too little, it will simply disappear beneath the water. On the other hand, if it's too steep, sediment will roll off without establishing a beachhead. It's all relative. What's steep in one place, under one set of conditions, would be judged gentle in another.

If beaches can be drowned, they can also be stranded. When continental land masses rise—as they did at the end of the last Ice Age—or when waters retreat in response to climate change (or other causes), beaches are sometimes left high and dry. Such "relict" or "fossil" beaches can be found in the Adirondack foothills of northern New York, for example, along with the skeletons of long-dead whales and seals. Today, sand from these fossil beaches is mined for use in aggregate. In the fullness of time, some of this sand ends up in streams and finds its way back to local lakes, where it helps to build new beaches. The earth's been in the recycling business for a long time.

But this isn't a surprise, is it? In the world of rock, wind, and water, the only constant is change, and one of the best places to get a feel for this is on the beach. Now there's a thought that's almost certain to bring a smile to any snow-bound paddler!

Copyright © 2002 by Verloren Hoop Productions. All rights reserved.

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