The fires in Yellowstone left a mosaic of areas greatly affected and others less so. Inside fire perimeters, large expanses of forest were completely untouched. There were three major types of burning. From an aesthetic viewpoint, the most destructive fires were the canopy crown fires that in many places obliterated entire forests. Crown fires accounted for about 41 percent of all the area that burned. Mixed fires burned both the canopy and vegetation on the ground, or burned one or the other as they spread through the forest. Ground fires spread slowly along the ground, consuming smaller plants and dead plant material; some ground fires burned for longer duration and intensity, contributing to the loss of many trees whose canopies were never directly burned.