Charles Ellicott Commentary Job 28:5

"As for the earth, out of it cometh bread; And underneath it is turned up as it were by fire." — Job 28:5 (ASV)

As for the earth ... —While the ploughman and the reaper till and gather the fruits of the earth on its surface, the miner far below maintains perpetual fires, as does the volcanic mountain also, with its fields and vineyards luxuriant and fertile on its sides.