DEPICTION OF GEOLOGICAL PROCESSES WITH ONTOLOGIES

Ontologies formally capture and specify domain theories (e.g., deformation) and knowledge about the world (e.g., shear zone). Every part of geologic reality includes a set of dynamic, spatio-temporal perdurant processes that involve a set of static and spatial endurant objects. Endurant objects, such as the San Andreas Fault persist, at each instant of time and spatial region, as complete, self-connected mereological wholes. Processes (e.g., mylonitization), on the other hand, occur during intervals of time (defined by events) through a succession of temporal parts called phase or stage. For example, ductile deformation in a shear zone may involve a phase of mylonitization which involves subprocesses of dynamic recrystallization followed perhaps by static recrystallization or cataclasis. This means that processes unfold themselves over time and, at each time slice (t) they present a mereologically incomplete part of the whole. For example, a snapshot picture of debris flow off an erupting volcano, taken at a specific instant of time (SNAP perspective), only shows an incomplete part of the whole flow which can only be seen through a video (SPAN perspective). While simple and aggregate endurants (e.g., mineral and accretionary prism, respectively) have spatial parts and boundaries, perdurants (e.g., crystallization, accretion) have temporal parts. For example, emplacement of an accretionary prism in a subduction zone may include offscraping, the duration of which includes phases in which rotation and translation of accreted rocks may occur. Processes, like spatial entities, can be organized in hierarchical structures using the taxonomic ‘is-a’ and meronomic (partonomic) ‘part-of’ relations. For example, cataclastic flow (a kind of ductile deformation) includes subprocesses of comminution and grain boundary rotation. Because of the spatio-temporal nature of processes, their representation in an ontology requires the notion of time (instant and interval). A geological process can lead to the destruction or change of spatial objects that participate in the process, or creation of new objects. The SNAP and SPAN perspectives provide views to the static and dynamic parts of the world, respectively, and allow us build effective ontologies that more completely depict our understanding of the geological reality.