Oh my. I think I found a bug.
Gamelog:
*** STARTING NEW GAME ***
** Starting Adventurer **
The Clerk stands up.
Utag Ciroudda, Clerk has been crushed under the collapsing ceiling.
You have discovered an expansive cavern deep underground.
You slam into an obstacle!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You slam into an obstacle!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You slam into an obstacle!
You are caught in a cloud of boiling magma!
You are caught in a burst of sandy loam!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a burst of loamy sand!
You are caught in a cloud of boiling magma!
You are caught in a burst of sandy loam!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a burst of sandy loam!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You slam into an obstacle!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a burst of loamy sand!
You are caught in a burst of clay!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You slam into an obstacle!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a burst of clay!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You are caught in a cloud of boiling magma!
You slam into an obstacle!
You have died after colliding with an obstacle.
I'm not entirely sure what happened here. I spawned, the game was super laggy, and then I think the ground exploded. Or rather, I think the game was super laggy because the ground exploded. I can't really see much; I appear to be in a 2zlvl pit, or at least I can only see 2 z's of it. I can't really see anything, as it is all obscured by either cave-in dust or smoke or something. It won't let me look at it, what with being dead and all. Maybe the caverns spawned here in such a way that the entire hamlet fell into the abyss, but that doesn't explain the BOILING MAGMA.
EDIT: Seems to be semi-replicable. At least, I started a new adventurer with the same civ and was beset by a wave of smoke (or something) and horrible lag. Steady 4 FPS. Fast travelling a few tiles to the North does not seem to be helping matters