crocodilage

CONT: Although heat is also a factor in the deterioration of asphalt on a roof, the real source of decay is the energy carried by the ultra-violet (UV) light of the sun, combined with the ready supply of oxygen in ozone. The ""links"" in asphalt molecular chains are hydrogen. The molecular bond is overcome by the strong attraction of the oxygen, which pulls the hydrogen away from the asphalt molecules. This process is called photo-oxidation, and these breaks in the ""aliphatic"" chain results in the shrinkage cracking common to asphalt. This phenomenon is commonly called ""alligatoring"" in roofing parlance, a term which describes the similarity of aged asphalt surfaces to an alligator's back.