thats a long way for that island to move, it could be a a cartographic error

Some maps contain deliberate errors or distortions, either as propaganda or as a "watermark" to help the copyright owner identify infringement if the error appears in competitors' maps. The latter often come in the form of nonexistent, misnamed, or misspelled "trap streets".[33] Other names and forms for this are paper townsites, fictitious entries, and copyright easter eggs.[34]