Assateague Island is in constant motion, with wind, waves, tides, and currents continually reshaping the island and its shores as sand moves, and these forces, combined with a gradually rising sea level, cause the island to shift a few feet westward each year. Over thousands of years, this migration has forced the island to repeatedly roll over itself through a natural process called overwash, in which severe storms send powerful waves across the island, dissolve primary dunes, spread sand over wide areas, and often wash it into the bay, temporarily burying dune, thicket, and marsh areas as marsh expands into the bay on new deposits and other island communities shift slightly west. Human development altered the natural dynamics of Assateague’s north end after a 1933 hurricane separated the island from Ocean City and stone jetties were built to keep the inlet from closing with sand; the north jetty trapped sand that would have reached Assateague, creating a beach wide enough for a new parking lot, while the sand-starved north end then migrated west at an unusually fast rate of 35 feet per year from 1935 until recently, compared with a normal rate of 3 feet per year. Although movement has slowed, action is needed to prevent the north end from merging with the mainland much sooner than it would under natural conditions. Old tree stumps that appear on the beach after storms show that the present shoreline was once an ancient forest on the island’s west side.