Board Thread:Questions and Answers/@comment-120883-20141128204017/@comment-13315666-20150625175213

Actually, come to think of it, the Japanese instruction manual for Sonic 1 stated that South Island drifts around the ocean. http://info.sonicretro.org/Sonic_the_Hedgehog_(16-bit)_JP_manual

So, I guess that during Sonic Chronicles it just happened to be right next to Central City. How convenient for Sonic and pals.