upon loading or creating a world my game will freeze up and crash

upon loading or creating a world my game will freeze up and crash

What I expected to happen was the world would generate and I could start playing

What actually happened was that the moment I hit "create new world" or "play selected world" the screen would freeze on a plain dirt background and the the game would crash after 5mins or so

Steps to Reproduce:
1. Open Minecraft
2. Hit play in the launcher
3. Select singleplayer or multiplayer
4. Load world
5. Watch game die