A heavy, bell-shaped mass of rock found in the roof of coal seams, typically formed by a fossilized tree stump. These smooth-sided structures are notorious hazards because they separate easily from the surrounding rock and can drop into the workings without warning.
Heard on the job
Watch your head in the crosscut, the bolters spotted a massive cauldron bottom and had to strap it tight.
Related terms
Kettle bottom
A heavy, cylindrical fossilized tree stump hidden in a coal mine roof that can fall without warning.
Roof
The layer of rock located immediately above an underground excavation or mineral seam.
Roofbolt
A long steel rod anchored into the ceiling of an underground excavation to prevent rockfalls.