Explaining phenomena associated with a system involves describing a system's structure and articulating the process through which the system's structure changes over time. This paper defines geo-sequential reasoning in the context of plate tectonics and uses it to analyse how students explain the geological processes that occur along convergent boundaries as part of the plate tectonics system. This study was part of design-based research on an online Plate tectonics module that included simulation-based modelling developed for secondary school students. We analysed students' explanations (n = 950) about phenomena found along a convergent boundary (1) as an oceanic plate and a continental plate move towards each other and (2) between two oceanic plates located on the opposite side of a tectonic plate from a divergent boundary. We also analysed images created by students of the simulation as evidence to support their explanations. We found that a majority of students used simulation-based evidence when describing the sequence of events along the convergent boundary and that the synced planet surface and cross-section views in the simulation supported students' inclusion of processes responsible for the events. These findings have implications for how teaching and research with dynamic simulations can support reasoning built with temporal evidence.