There's 2 options for this:
If it's just happened contact Help and ask for a Rollback to before your saved game got messed up.
It takes your game back to how it was before it broke, but you lose everything you tapped for since.
Leave it too late and that's a bad idea.
The other option involves you fixing it yourself, but it'll be slow going.
Start Furthest from Mountains and Ocean if things shifted down, or where the Ocean meets the Mountains if things shifted up. Use the Crossed Arrows button to go into Design Mode, tap everything in the Right Hand menu to turn those off except the Ground Tiles at the top making sure you scroll and get all of them. Now use the Area Select tool to put those shifted tiles back where they belong and move across before moving down ( or up ) so they don't collide with tiles you haven't got round to moving yet.
Sorry, it will take a while doing that, but you could do a bit at a time until it's all fixed.