Chunks raised from the ground

Upon logging into a world, I found my character suffocating in stone, though I was able to free the character, I found that several of the surrounding chunks had a strange effect. Several seemingly random chunks were raised from the ground. I am not sure if they are the same chunks as before, but with a different elevation, or if these are completely new chunks all together.

I have limited ideas on what triggered the bug, due to there being no modification on my version of the game, but it the bug seemed to take place when I logged onto the world.