## 4 Virtual Geosites Sharing (WebGIS Platform)  
In this section, we present an innovative approach to make Santorini's VGs accessible worldwide through the internet, together with a wealth of information suitable for highlighting and explaining the geological features and processes observed on the island. To this end, we combined a WebGIS platform with 3D models available in virtual reality, as detailed below. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Virtual Geosite** & **Nr. of Pictures** & **Nr. of GCPs** & **Texture Resolution (cm/pix)** \\ \hline VG1 & 1231 & 4 & 1 \\ \hline VG2 & 929 & 4 & 4 \\ \hline VG3 & 493 & 4 & 2 \\ \hline VG4 & 350 & 4 & 4 \\ \hline VG5 & 300 & 4 & 4 \\ \hline VG6 & 6736 & 34 & 2 \\ \hline VG7 & 1500 & 4 & 1 \\ \hline VG8 & 36 & 0 & 6 \\ \hline VG9 & 35 & 0 & 6 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of the relevant details for the nine VGs, including the number of pictures collected, the number of GCPs used for referencing and scaling, and the final texture resolution. To more efficiently disseminate all available models amongst the cooperating parties and the general public, we had to use a dedicated media through which the models can be properly grouped and shared. After looking into the available options, and thanks to the consortium's previous extensive experience with ESRI products, the ArcGIS Hub platform ([[https://hub.arcgis.com/](https://hub.arcgis.com/)]([https://hub.arcgis.com/](https://hub.arcgis.com/)) (accessed on 10 June 2021)) was deemed the best choice. ArcGIS Hub, developed by ESRI in 2020, is a platform that allows for the creation of interactive sites through which an organisation can share its spatial content. All team members can customize and enhance the developed site with 2D and 3D maps, smart layouts, templates, and multimedia content that can be configured to better showcase the available information. External media, and other applications developed within the ESRI platform, can be added. An educational account was used to create the virtual geosites hub accessible at: [[https://arcgis.is/1e4](https://arcgis.is/1e4) erK0]([https://arcgis.is/1e4](https://arcgis.is/1e4) erK0) (accessed on 10 June 2021). In the present case, narration starts with an eye-catching photograph of the Santorini panorama combining natural and anthropogenic environments, followed by a short introduction on the hub's purpose. Scrolling down, the user can view an interactive 2D morphological web map outlining the location of the selected geosites (Figure 2). A 5 m resolution digital elevation model from the National Cadastre and Mapping Agency S.A. of Greece was rendered according to elevation. A multidirectional shaded relief map was also used to represent the onshore morphology. Concerning offshore morphology, a 16 m resolution grid [41; 50] and a multidirectional shaded relief were combined to show the unique seabed of the area thoroughly. The users may select a VG location on the map to obtain further details. Figure 2: Screenshot showing part of the hub created for Santorini’s virtual geosites. An interactive 2D morphological webmap outlines the location of the VGs. The users can select a location to obtain more information. A brief overview of the island's volcanic history, accompanied by a 3D simplified geological map, modified from [PERSON] et al. (2018), are provided. The viewers can use the tools on the map to zoom in and out, or right-click anywhere on the map to tilt and rotate the scene, observing it from different points of view (Figure 3). Both the two-dimensional and three-dimensional (scene) web maps were created through the ArcGIS Online platform (www.arcgis.com (accessed on 10 June 2021)). The final part is dedicated to a gallery that includes all nine virtual geosites (Figure 4). Buttons allow the user to access a StoryMap application about each VG.