Sand dunes along the North Carolina coast are an integral part of the ecosystem immediately adjacent to the sea. The dunes are formed when sand particles that have been washed ashore are picked up by the wind and blown inland until an obstruction is encountered. The obstruction usually consists of some form of jetsam that has been deposited high up on the beach during a storm, though it can also be types of vegetation. Eventually, the dune itself becomes enough of an obstruction to block the windblown sand.