The special issue comprises contributions on recent advances in either experimental or numerical modelling, or their combined application, in the context of geophysical flows. This includes, but is not limited to, mudflows, debris flows, debris avalanches, landslides, pyroclastic density currents, and volcanic plumes and their interaction with the atmosphere. The contributions should focus on pioneering experimental methodologies, comprehensive model validation studies, and detailed investigations into the challenge of upscaling from laboratory-scale experiments to field-scale geophysical flows. The special issue arises from the Cities on Volcanoes 12 workshop From the laboratory to the natural scale in debris flows hazard modeling: the challenge of upscaling (17 February 2024) and the EGU2024 session Advances in Understanding Volcanic Hazard and Environmental Impact (14–19 April 2024).