Request a Tutor Become a Tutor Decomposition is a biological process that breaks down dead organic matter into simpler organic and inorganic substances. In Archaeology, there are four key stages of decomposition: Hypostasis, Algor Mortis, Rigor Mortis and Putrefaction. To excel in this subject and improve your archaeological skills, check out the list of skilled decomposition tutors in Upper Hutt central business district, Upper Hutt.