As I was in my world about a 10 x 13 chunk of underground popped up from the ground. It was weird and you can walk through them! They are ghost blocks because they look real but you cannot destroy them. If you update the block or a block in them it dissapears but comes back some time or another.
Please fix!

Picture #1: Outside of the chunk.

Picture #2: Inside of the chunk you can see ravines, lava stuff like that through the ground.

Picture #3: Looking at the blocks from inside the chunk.

Picture #4: Looking 1/2 in 1/2 out of the chunk.