This has happened in a couple of different places on my server. Does anyone have any idea what causes it to happen?
Some facts about the phenomenon:
- other players on the server can't see them, only I can
- other players can walk out onto the ground that's supposed to be there
- animals can also walk out onto the missing ground, but their movement becomes sporadic
- several holes can appear very close to one another
- after leaving for some time, and then returning, the hole may be gone
- mobs can sometimes be seen walking along the bottom of the recess
- there appears to be a room (possibly a dungeon) suspended in the middle of the second one
- these are incredibly creepy
I haven't been brave enough to venture out onto one yet, but will try and post results.
Edit: It turns out when you fully jump into one, you fall the length of a block, and then you're pushed back up again. This happens repeatedly, and very quickly, so that you get stuck midair and have to /tp to get out.
Also, the hole in the second picture came back, but there is no longer a big room at the bottom.