Where the Straits of Georgia and Juan de Fuca meet the Sound of Puget, the tides rushing in and falling out swirl round myriad peninsulae, islands, and rocks. On the rise, they reverse the course of even the mighty rivers twice a day, pushing into inlets and sloughs, fjords and marshes. As streams and rivers deliver sediment by the daily mote and occasional landslide, as bluffs calve and slump down to the shore, the tides grab rock and sand, smudging it around each cliff and dune, softening the drop into the deep. Carbon in the forms of leaves, seaweeds and logs rides tides and storms to the high water mark, adding to the littoral, the liminal that separates and unites land and sea: the beach.
Slow that story down, stretch each hour to a millenium or two, and it plays out with tides of ice. Glaciers carved out much of the sea, drowned land under grinding flows and ebbs. Each advancing lobe plows deeper while the sheer weight pushes the bedrock down. When the climate warms, the glaciers retreat, barfing collosal slurries of meltwater, rock and grit as they do. Freed of the weight and exposed to Northwest rains, the land beneath rebounds and erodes downstream. Sometimes, the glacial pace speeds up with a rushing river beneath the ice, or collapse of an ice dam that unleashes great lakes all at once.
On either scale, rocks and organics end up along the shore and on the floor of the Salish Sea.
Meanwhile, the sea sends up it's contribution. Creatures crawl up, seaweeds drift in and hold fast. All those rocks become covered with coatings of single-celled organisms, draped with flaccid primitives, crawled over by critters with exoskeletons, all while the clams and their kin burrow down and spit up sand (all of them poop, or die, or both, adding to the beach). On a low tide, the land normally hidden by the sea's glare and motion emerges, occupied over every inch in stark contrast to the plain plane of water we normally see on the calm Salish Sea. No wonder the local people have always said that when the tide is out, the table is set.
Set the table these days with these beach denizens, and you may find people saying that they ate already. Let Bourdain eat the barnacles, or that thumbheaded Bizarre Foods guy enjoy the salty cartilige-covered-in-slime texture of the limpet (well OK, Hawaiians will take the latter with gusto, but for the most part, moderns have narrowed down the list of edible shellfish to a handfull). But look at the species spread in many an old shell midden, and what you find is diversity closer to what lived on the beach than what a modern table holds. That's what happened when people needed the beach and it's life in order to live themselves; that's how it was before oyster and geoduck became conspicuous and expensive consumption.
Of course, seeing these old sites has become harder. More than a century ago, many were dug up and hauled away to burn the shell for lime, or fed to chickens to make their eggshells harder, or just piled up in dikes to "reclaim" the marshes that fed previous generations. Later, people took to armoring the shoreline, strangling natural beaches beneath fill and junk while what once stretched in front was washed away. People who believe that they own a piece of the earth want to build right up to the line, and in so doing wiped away that magical stretch of neither-land-nor-water that any good beach embodies.
For a variety of reasons, the Northwest has escaped widespread sea level rise thus far, but it will not forever, and future storms will wipe away the archaeology that could tell us how people adapted to previous changes in climate. A shift in the winds, a subduction zone quake, and the wisdom of millenia calves away, pulling certain kinds of knowledge out of reach. I've seen coastal sites that are within a few storms of disappearing entirely. Meanwhile, the agency responsible for archaeology has poured resources into studying buildings on the shore and promoting them as tourism magnets, with no perceivable effort to document and learn from the older coastal sites and what they could mean for our well-being and survival.
Beaches will always exist (they will replace the buildings when we are gone, surely as the tides will continue to flow and ebb), but the beaches that we can learn from, the ones that tell the stories of how people dealt with climate change or tsunamis, for example, are eroding, their creatures thinned to a faint shadow of their former abundance and diversity by the ongoing acidification and extinctions.
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