A chunk appeared above the ground, It's not hollow and there's solid ground under the chunk. it also changed the nearest chunk and from the looks of the grass its now a mountain biome or something. I dug under and into it to show that it's not hollow to explain the pictures of holes.
Environment
A grassland not too for from my house/base and a walled off village. The grassland is surrounded by dark oak forests.
Duplicate of MC-2545
Likely a disk issue.