The most damaging weathering force is sunlight. After the fleshy portion of an individual is gone the skeleton is left without protection from the sun. The main types of damage caused by sunlight are bleaching, shrinkage, and warping.
Sun bleaching occurs when a bone is left on the surface of the ground or is only partially buried. Bone that is exposed to sunlight will undergo discoloration, taking on a bleached or whitened appearance.