take a look at this, the chunks are corrupted, there are some chunks generated as superflat
Environment
i generate a normal world without mods
MC-80849
bad creation world
Resolved
Duplicate
0
Thank you for your report.
However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-315. You can find or add further information on that report.
Please search before reporting any bugs, as it's likely that one exists already.