Recent storms unearth remnants of ancient swamp on Cape Cod

By Todd Feathers, Globe Correspondent

After the furious February storms that roiled the ocean along the coast, a “primeval” scene emerged from the sand of Coast Guard Beach in Eastham, a National Park Service official says.

Waves tore away beach sand, revealing the soil and trunks of an ancient white cedar swamp. Bluffs along the beach were also sliced by the water and cross-sectioned, revealing not only the swamp’s peat layers, which may be thousands of years old, but also clay deposits beneath them, which may date back to before the last ice age, said William Burke, a historian and program manager with the Cape Cod National Seashore.

“Envision a swamp with these tall cedar trees in it,” Burke said. “Year after year, the pine needles and organic matter drop into the water and get compressed into the peat that you’re seeing washed up on the beach now.”

A small 7-by-10-foot portion of the swamp had been visible on the beach for some time, he said. But the storm uncovered a much larger swath, perhaps 225 feet long and 25 feet wide.

There are several white cedar swamps on Cape Cod, Burke said, but they are exceedingly rare. The swamp uncovered at Coast Guard Beach appears on maps drawn as recently as 1848, but is likely much older than that.

Burke said that perhaps just 20 percent of the swamp is now exposed, although he admitted that was a rough estimate.

Sand will probably seep back into the exposed area, covering the dark, slippery mass of peat within the next four to five months, Burke predicted. But as the ocean slowly erodes the Cape, the swamp will gradually disintegrate.

“Little by little, this peat deposit is going to get torn away, tossed out into the water in millions of little pieces,” he said.

Researchers and beachgoers must enjoy the ancient muck while they can.

Todd Feathers can be reached at todd.feathers@globe.com. Follow him on Twitter at @ToddFeathers.