I just opened up a new world on Minecraft and I just saw this...
What I expected to happen was...:
Just the normal terrain generation... What else?
What actually happened was...:
How the heck did a mineshaft get here?
Steps to Reproduce:
NOTE: I think it's rare, but here are the steps anyway...
1. Just make a new world
Works as intended. This is part of the new superflat generation in 1.4