A bug in the world generation: floating snow layers.
Expected behavior:
Snow layers should only generate on top of a block.
Steps to reproduce:
Create a world with seed 155641330981648524
Go to 1797 -28
Notice the floating snow layers
Might be related to https://bugs.mojang.com/browse/MC-610
These are common glitches, Simply place a block next to all the snow and they will disappear.