MIMMOC

This virtual special issue is based on the presentations and discussions that took place at the International Geographic Union (IGU) Centennial Congress, held in Paris from July 18 to 22, 2022. The Congress was organized locally by the Comité National Français de Géographie (CNFG) around the theme "Time for Geographers." Participants were invited to consider on how geography, which focuses primarily on terrestrial spatial issues, also deals with time. Among the 263 working sessions, the CNFG Geomorphological Heritage Commission, in partnership with the IGU Geoheritage Commission and with the support of the Working Group on Geomorphosites of the IAG (International Association of Geomorphologists) organized a session entitled "Time Scaling Issues in Geoheritage Studies". The session was chaired and moderated by Claire Portal, and co-chaired by Fabien Hobléa and François Bétard, with the participation of Benjamin van Wyk de Vries and Dongying Wei. This special issue features six research papers based on the reflections of the session.

Participants were invited to examine questions of temporal scale, which are of fundamental importance in geoheritage studies, but whose various aspects are little considered in their own right. Indeed, it is the spatial dimension of geological and geomorphological sites (e.g., geosites in this editorial) that is more particularly studied; the complexity and interweaving of geoheritage spatialities (from outcrop to landscape) are the subject of numerous publications (for international journals, see among others the International Journal of Geoheritage and Parks and Geoheritage). While questions relating to temporal scales are explicitly developed in various studies (e.g., Reynard, 2009; Giusti & Calvet, 2010; Martini, Zhang, Gu, & Li, 2013; Bétard, Hobléa, & Portal, 2017; Coratza & Hobléa, 2018), these remain a minority in the profusion of publications on geoheritage. Most often, time and its scales seem to be integrated de facto. They rarely constitute a subject of reflection in their own right. As F. Hartog writes, referring to historians' practices, "time has become commonplace for the historian who has preserved or instrumentalized it. It is not considered because it is inconceivable, but because we do not think of it or, more simply, we do not think about it." (Hartog, 2005, p. 7). However, temporal scales are a particular feature of environmental heritage: they interweave the temporalities of nature with those of culture, both historical and human. Theoretically, a geo-heritage element can tell its story from the creation of the planet to the present day, and into the future, depending on, for example, its evolution, its degree of vulnerability and, if they exist, the protection operations that have been put in place. The temporal aspect is therefore central to the selection of geosites, to the implementation of conservation and management measures, and to the production of interpretation tools. Thus, in order to understand the temporal dimension of geoheritage, two fields of study emerge, one more theoretical on the time of geoheritage taken in its broadest sense (including the geoheritage-making processes as a function of time), the other, more practical, on the time of geosites.