## 4 Virtual Geosites Sharing (WebGIS Platform)
The value of using such applications to illustrate and promote the proposed geosites was based on previous related applications of this kind and especially the ones employed by some of the authors of the present work (2018; 2019; 2020). ESRI provides several configured apps ([[https://storymaps-classic.arcgis.com/en/app-list/](https://storymaps-classic.arcgis.com/en/app-list/)]([https://storymaps-classic.arcgis.com/en/app-list/](https://storymaps-classic.arcgis.com/en/app-list/)) (accessed on 10 June 2021)) and a new StoryMap template ([[https://storymaps.arcgis.com/](https://storymaps.arcgis.com/)]([https://storymaps.arcgis.com/](https://storymaps.arcgis.com/)) (accessed on 10 June 2021)) combining popular features from those previously mentioned, to be used as story maps. The second approach, called ArcGIS StoryMaps, was employed, featuring a user-friendly interface that has a responsive design and enhanced capabilities to incorporate 3D visualization. Furthermore, the ArcGIS StoryMaps template has many important accessibility functions to support viewers with impaired vision or limited mobility. Each StoryMap developed combines descriptive information and the corresponding 3D model; credits and references are also mentioned in each one (Figure 5). Figure 3: Screenshot showing the part of the hub dedicated to the volcanic history of the island. The users can tilt and rotate the 3D interactive map to view the scene from different points of view. Figure 4: Screenshot showing the part of the hub where the users can access each VG. Using each button, the viewers can access, inside the hub, a dedicated StoryMap application, where descriptive text and the 3D model can be found. Figure 5: Representative screenshot of the StoryMap that corresponds to the Cape Epta Paides virtual geosite. Users can return to the main page by using the “Virtual Geosites” button in the upper-left side. To be embedded in the StoryMap, a model must first be uploaded on an online 3D viewer. The Sketchfab platform (educational license), allowing for a stunning viewing experience through the immersive virtual reality (VR) [1,2,80], was used for our work. The viewer can access 3-D visualization on a computer [6], tablet, or smartphone, in this case, through non-immersive VR. Furthermore, augmented reality (AR) items can be added as scientific annotations [81]. According to [82], the uploaded material can be used for non-immersive VR experience of each model on a PC screen or a mobile device without head-mounted displays; on the other hand, a fully immersive VR experience can be obtained, which guarantees more effective interactivity, utilizing head-mounted displays such as goggles and VR headsets. To enable the viewer to experience a 3-D visualization, each VO was uploaded on the Sketchfab platform with a straightforward drag-and-drop procedure; Sketchfab automatically builds the 3-D scene, which is almost ready for non-immersive visualization; a number of settings can be adjusted, regarding the initial view, field of view, model orientation, light/shadow, etc. Furthermore, by employing the Sketchfab platform, each model can be explored through the embedded immersive virtual reality (VR) tool; VR contents can be made available for many devices: Google Cardboard and more generic VR Goggles for mobile phones, HTC Vive, Oculus Rift, and others ([[https://sketchfab.com/virtual-reality](https://sketchfab.com/virtual-reality)]([https://sketchfab.com/virtual-reality](https://sketchfab.com/virtual-reality)) (accessed on 10 June 2021)). To make it possible to enjoy a more effective, immersive VR experience, the viewer's starting point, the height, and the direction of observation, need to be set (e.g., Figure 6). The user can observe the model through an immersive VR experience and move across the scene by selecting the annotations to explain the most relevant features in each model. The hub concludes with a footer, naming the consortium members and providing contact information.