So I have my own server to be a hermit in, and after deeding I made myself a mine. It was a terrible mine and took me days to find any iron, but yesterday I finally did it. Now I shut down my server when I'm not using it, and I'm the only player. Today I started up my server again, and after doing a bit of smithing I turned around to see ABSOLUTE CHAOS. My mine entrance had collapsed, but in a way I've never seen before! It had turned into a massive pit, hitting the water table below. Now I've (hopefully) fixed the terraforming with my GM so I can get mining again, but what on earth happened? Why did my mine collapse by itself like this? Is there anything I can do to prevent it happening again?