What Is Colluvium?: An Interactive Poster Seeking a Common Definition to Improve International Communication.

Parent material is recognized as an important factor in describing soils and understanding their pedogenesis. Therefore, for international innovation to occur, it would be highly beneficial to have a common understanding about the terms used to describe parent materials. Among parent materials, colluvium can be particularly influential as it is recognized in some national classification systems (e.g. France, Germany) as diagnostic material for “Colluvisols.” However, colluvium is a term with a great amount of variability in meaning among geoscience disciplines and regions, which also affects the meaning of the term alluvium. Clarifying the meaning and diagnostic criteria of colluvium is especially important today because some definitions connect it directly to erosion processes that are wide-spread and enhanced by anthropogenic activities. For example, the German “kolluvium” is pronounced the same as colluvium, but describes deposits at the base of hillslopes produced by water and/or tillage erosion. This contrasts with the common North American definition of colluvium describing materials transported primarily by gravity (i.e. mass movement). This poster first attempts to summarize the variety of definitions for colluvium. Then it begins an experiment of asking viewers to identify the terminology they would use to describe materials related to colluvium in a series of model landscapes. The viewers are also invited to join the discussion on the same question, posed on the ResearchGate website (https://www.researchgate.net/post/How_do_you_define_colluvium).