A thin peninsula called a spit extends beyond the bluffs of the outer beach on Cape Cod. What has caused this spit to form? View Available Hint(s)for Part C Sand from the bluffs is carried and deposited by longshore currents. When beach dunes become separated from the mainland by an intervening stream, a spit forms. Barrier islands that migrate are known as spits. Nor'easter storms cause larger landmasses to erode into long, thin ridges known as spits. As sea level drops during the winter, shoals are exposed. These are known as spits