The island was created as an outwash deposit during a brief pause in the last glacial retreat from melt water runoff carrying eroded sand down a stream from the high hills (Love Lane and Cowesett Hills area) forming a navigable river mouth called Arnold's Cove (cc.
The shore along Chepiwanoxet once was one long winding sandy beach continually fed by erosion of the many high hills along the bays West coast.