Many parts of Europe are exposed to tephra hazards that jeopardise regions around volcanoes and the continental airspace. Quantifying and mapping the impacts from future eruptions is relevant to aviation stakeholders and to national and regional civil protection administrations and agencies. This paper presents a novel methodology for long- and short-term Probabilistic Volcano Hazard Assessment (PVHA) from tephra based on a large catalogue of footprints and associated metadata, each footprint representing a single-scenario model realisation. The methodology is used to generate a first version of the European Tephra Hazard Map (ETHM), a collaborative initiative aiming at providing single- and multi-volcano mappings consistent and homogeneous across spatiotemporal scales and volcanoes. More than 53,000 footprints from 12 European volcanoes were computed by running the FALL3D atmospheric dispersal model on the accelerated partition of the MareNostrum-5 supercomputer. In regional model nests (2 km model grid resolution), footprints identify areas prone to hazardous tephra fallout. At European scale (10 km model grid resolution), footprints delineate hazardous airspace regions in terms of ash concentration at critical flight-level layers. The catalogue of footprints is stored in a Simulation Data Lake (SDL@CINECA) to ensure accessibility and re-usability, as well as to ease the addition of footprints from other volcanoes in the future. In parallel, a lightweight service facilitates downstream hazard mapping and dynamic update of hazard based on user-given Probability Density Functions (PDFs), decoupling the computational workload of simulating the physical process from the actual hazard quantification.