There is a bunch of blocks that are corrupt.

Well, when I play Minecraft, Across the river from my little town, there's a giant group of corrupt blocks. It looks like a big black square that has a blue bottom that I can't move down in to it. Ever since these blocks have been there, the game has been freezing and crashing. Sometimes I can't even get on to mine craft. When I select my world, it sits there for a few minutes. Then, It goes back to the title screen. Also, Thousands of Cattle randomly generate (See photo)