Nature's alterations to the landscape never end, and mankind gets in the way.
Billingsgate Island, once the site of a lighthouse, a school, and over 30 houses, is now Billingsgate Shoal. It used to be a popular picnic destination, big clambakes.
Some of it is above water now, during low tides. Best explanation I've heard is that destroying the salt marshes that protected it from Cape Cod Bay (for salt hay to feed the critters) is what destroyed it.
This photo shows what agriculture and deforestation (by the Indians and then by the Europeans with their farms and cattle) did to the soil of the outer Cape: it's down to sand and sweet-smelling scrub now:
Interesting piece on the topic below the fold -