I was building an ice farm when this happened. It was snowing, and a few snow layers fell on the snow ground. I was looking at the white trees, when suddenly the block I was standing on disappeared. Actually, the whole snow ground I was on disappeared, and all the snow layers went down by one block (image 1). I then fell off the snow (image 2), and it started disappearing (image 3) (maybe because floating snow layers aren't supposed to exist). For some reason, the 2 high snow wall with torches on top you can see on the left of the first picture wasn't affected. Only my ground and the staircase I built to get there disappeared. Before the bug, the farm looked like (image 4).

Steps to reproduce :
I have no idea of what caused this. The two most likely causes are the snow falling from the sky and the fact that I had built a 1 block high snow platform. I couldn't try to reproduce it because it never snowed again.