I made a world in an earlier 1.8 snapshot but it suddenly generated this higher land I definitely had not seen before. What happened was that when I entered the world, there were many chunks that had 'sprouted' from y:64 to y:237.(it was a flat world)

Snapshot Used after error: 14w32d
Snapshot Used before error: ? (possibly April snapshot)
World Type: Superflat (Overworld preset)
Seed: 2801832057485171305
No. of chunks affected: 404
Date world last updated before error: 12 Apr 14
Note: command blocks in photos were meant for adventure map