Sarichef Island (on which Shishmaref is located) is part of a dynamic, 100 km-long barrier island chain that records human and environmental history spanning the past 2000 years; the oldest subaerial evidence for the formation of this system is about 1700 years before present, according to carbon 14 dating (see References, below). Erosion at Shishmaref is unique along the islands because of its fetch exposure and high tidal prism, relatively intense infrastructure development during the 20th century, and multiple shoreline defense structures built beginning in the 1970s.