In addition to locally thickening the coal, the tightness of small scale folding in the mine, along with possible faulting, would have broken surrounding sandstone layers and forced pods of sandstone into the more ductile coal. As mentioned earlier, folding around the Altoona mine is not the result of the mine being between Little Walker and Tract Mountains. In actuality, the fold on which the mine is situated has developed along one of at least two thrust fault structures that climb out of the Devonian-aged rocks into the coal-bearing Mississippian aged rocks at the mine.