By comparing the 1987 and 1993 aerial photos, large areas (orange) where forest had been cut were apparent. The smaller squares were oil drilling patches. Larger areas were converted to agriculture. The common practice at the time was to knock down even large trees with a huge bulldozer and pile up the wood into an immense pile. In November after the first snow, a torch was applied and the piles of wood were burned. The next summer the bulldozer dug a large hole, pushed the ashes and remaining parts of trees into it, then covered all with soil. Only later was it discovered that aspen are valuable for making oriented strand board. Red squares are 10 acre patches of ground cleared to provide a buffer around recent oil wells that dot the countryside.