## 3 Immersive VR and GeaVR Visual Discovery Framework  
Virtual Reality (VR) was first introduced in 1962, as a computer-generated simulation of a three-dimensional environment that can be interacted with in a seemingly real way by persons using special electronic equipment, such as headsets with screens inside or gloves fitted with sensors. This earliest VR system was provided by [PERSON], US Patent #3,050,870; this system was named \"Sensorama\" (Figure 4a) and it supported multi-sensory technology. Nowadays, following the definition from [PERSON] et al., (2016) [53], VR can be distinguished in two types: non-immersive and fully immersive VR (IVR). The former displays 3D models on a computer screen or mobile device without using any head-mounted displays, typically referred to as 3D visualization (e.g., [54]). The latter enables greater interactivity, through VR headsets and goggles (e.g., Figure 4b). The technical maturity reached in the evolution on modern game engine platforms, combined with lower costs of VR devices now allow creation of immersive VR environments in a variety of application contexts such as teaching and learning in education, professional training in industry, scientific research and public outreach [55; 56]. The IVR approach has been fully developed for Earth Science by [PERSON] et al., (2020) [10], in the framework of the Italian Argo3D ([[https://argo3d.unimib.it/](https://argo3d.unimib.it/)]([https://argo3d.unimib.it/](https://argo3d.unimib.it/))) and European Erasmus+ 3 DTelc ([http://3 dtelc.lmv.uca.fr/](http://3 dtelc.lmv.uca.fr/)) projects; in addition, [PERSON] et al., (2018) [32] and [PERSON] et al., (2019) [33] gave a contribution over time, providing scientists with novel navigation mechanisms for exploring outcrops in a fully immersive way, offering the possibility to also interact and collect measurements, thus replicating real world field activities. The resulting software is named GeaVR, which is an offline-based Visual Discovery Framework developed with the Unity ([[https://unity.com](https://unity.com)]([https://unity.com](https://unity.com))) game engine, employing an Oculus Rift ([[https://www.oculus.com](https://www.oculus.com)]([https://www.oculus.com](https://www.oculus.com))) as a head-mounted VR device, allowing earth scientists to navigate, interact and perform measurements in their own immersive VR scenarios, based on photogrammetry outputs (e.g., 3D Digital Outcrop Models) as well as freely available Digital Elevation Models (DEMs) and Digital Terrain Models (DTMs). Both technologies are widespread and provide good examples for developing software such as the one presented here. GeaVR can be relatively easily ported to other game engines or headsets. Through GeaVR, it is possible to perform complex geological investigations and massive quantitative data collection into scalable models, focused on: surface attitude, topographic profile (e.g., considering the 3D surface), mapping of points of interest, lines, polygons, pictures, etc. All the available tools allow users to export scientifically correct data collected during a IVR session, offering the possibility to interoperate with external software such as GIS and Google Earth. GeaVR will be made available at [[https://geavr.eu](https://geavr.eu)]([https://geavr.eu](https://geavr.eu)), for non-commercial use and after registration. GeaVR provides to end users a holistic view of the area of interest (e.g., [32]) by allowing the exploration of specific features from several points of view and at a range of different navigation modes (e.g., Figure 4c) while supplying a toolset to simulate field activities in both onshore and offshore environments (Figure 4d). In this research, we have built up the ad hoc VR scenario for the Metaxa Mine using photogrammetry approach, to map the different volcanic phases and measure their thickness and also to map debris flows and anthropogenic debris.