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.
Shrinking occurs when the moisture of bone has evaporated and bone begins to decrease in size. Often times the cortical bone (top surface of the bone), which is exposed to more sunlight, shrinks at a faster rate than inner layers of bone. This causes tension between the bone layers of bone and results in cracks. Warping is caused by the differential drying rates of different segments of bone. Typically a bone will bend to the side that has lost the most moisture.