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The West Virginia Encyclopedia
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The West Virginia Encyclopedia
The term kettle bottom, in miners’ jargon, refers to a dangerous geologic formation found in the roofs of underground coal mines. Kettle bottoms increase the risk of mine roof falls.
Kettle bottoms were generated in ages long past when an underground mineral deposit formed inside of slate, or when the root mass of an ancient tree petrified. The kettle bottom creates a single compact mass which can shift or even dislodge itself from the surrounding slate and fall. Kettle bottoms pose a deadly danger because they are difficult to detect and usually fall without warning from the mine roof. Any disturbance to nearby rock strata, such as drilling or even striking the mine roof with a hammer to determine stability, causes vibrations and increases the risk of the mass falling. Early miners described the empty space left after a kettle bottom fell as looking like the interior of an inverted kettle.
The risk associated with the kettle bottom itself falling, or the instability caused in the surrounding roof after a fall, creates mine safety problems. Roof bolting can be particularly dangerous in areas where kettle bottoms are present. Heavy timbers are generally used to brace kettle bottoms while permanent roof supports are installed.
Written by Shae Davidson
Chase, Frank E. & Gary P. Sames. Kettlebottoms: Their Relation to Mine Roof and Support. Washington: U.S. Bureau of Mines, 1983.