Coal mine gob. mined-out areas in underground coal mines. often accumulates explosive methane-air mixtures that pose a deadly hazard to miners. A good understanding of the flow field in a sealed coal mine area is crucial in preventing and minimizing accidents associated with mine combustible gases and also for planning and implementing a mine rescue strategy. https://www.markbroyard.com/hot-sale-us-topo-7-5-minute-map-for-sunken-lake-mi-supply-limited-grab/