World Generation Issues

When reopening a map I have been playing on for about a week (created May 17), the world generates with seemingly rearranged chunks. There are a lot of perfectly flat cliffs showing the insides of abandoned mine shafts and the like, some leaves that were previously connected to a tree are now on a different part of the map, about half of my house has a copy of itself about 50 meters away, etc. This is on single player.