Sable: Collapsing Caves

A cave-in starts from a chance roll, for each eligible spot one in 512, after a three second warning. The rules decide where a cave-in is allowed, a height limit keeps it away from the surface, and a grace period and a cooldown stop it from repeating too quickly. Once started, a cave-in splits into three sizes, and each size has its own distances. Pieces that break away are handled by Sable physics, so a piece that receives a small push can come away from the ceiling and roll into a corner, and falling blocks reach more damage the farther they drop. Blocks that lie in the path of a fall suffer harm, and blocks that cover a player cause suffocation damage.

Sable: Collapsing Caves requires Sable, and it can also use Sable: Ragdolls, which the author recommends. Sable: Collision damage is an optional addition. Servers that run it need every player to install it too. Files are published for NeoForge only, for 1.21.1, under the CC0 1.0 Universal license, which is not open source. The mod keeps about 300 physics blocks active during a cave-in, and when that number is exceeded the oldest blocks return to the world to make room for new ones.