Geological heritage or Geoheritage includes "pure" geological and geomorphological heritage, representing the entity of unique features of the Earth's crust that can be employed for the purposes of science, education and tourism [1]. Geoheritage has different types (geomorphological, sedimentary, igneous, etc.) and forms (natural outcrops and landscapes, etc.), which is the subject of geoconservation.
Two main types of localities exhibiting geoheritage that are officially designated are geosites and geoparks. The former are relatively small objects or areas representing unique phenomena. Geoparks are areas specially designated for geoheritage exploitation for the purposes of tourism, education and science, as well as for their conservation [1]. Additionally, geoparks bring jobs to rural and indigenous people, in turn helping to protect sites of importance and promote geoheritage. UNESCO (United Nations Educational, Scientific and Cultural Organization) Global Geoparks are single, unified geographical areas where sites and landscapes of international geological significance are managed with a holistic concept of protection, education, and sustainable development. Their bottom-up approach of combining conservation with sustainable development while involving local communities is becoming increasingly popular. At present, there are 169 UNESCO Global Geoparks in 44 countries [2]. The distribution of UNESCO Global Geoparks around the world is presented in Fig. 1. It shows that current UNESCO Global Geoparks are mainly distributed in southwestern Europe and eastern Asia. Among them, the volcanic Global Geoparks are mainly distributed in China, Japan, Korea, Peru, and Turkey [2].
One of the geoheritage features, the volcanic fields, which are widespread on Earth, such as scoria cones, tuff rings, maars, lava flows and lava lakes, help to increase in interest and wealth of new science knowledge [4]. The establishment of volcanic geoparks and geoheritage sites is becoming increasingly popular worldwide. UNESCO Global Geoparks and the European Geopark Network have numerous geoparks which achieved their status due to their volcanic geoheritage [4].
The Saudi Arabia, with an area of 2,250,000 km2, is ranking the 14th in the world. Induced by the expansion of the Red Sea, Saudi Arabia has developed at least nine Cenozoic basaltic volcanic fields in the western part, with a total area of 180,000 km2 [4]. However, there is still no geoheritage site in Saudi Arabia that has been inscribed on the UNESCO Global Geoparks.
The Al-Medina volcanic field (AMVF), part of the Harrat Rahat in northwest of the Saudi Arabia, is the worth notable active volcanic field characterized by the occurrence of two historical eruptions approximately in 641 and 1256 AD. The evolution, lithology, geochronology, geochemistry and the hazard analysis on the region [5,6,7,8,9] have provided important information to the inventory of the volcanic heritage. Here, we identify significant volcanic features in AMVF by using multi-source satellite images, including Moderate-resolution Imaging Spectrometer (MODIS), Landsat-8 OLI (Operational Land Imager) and China Gaofen-2 (GF-2) data. The results of our studies indicates that the AMVF could be organized and promoted as the UNESCO Global Geopark in the Kingdom of Saudi Arabia.
Remote sensing data products (aerial photographs and satellite images) give direct information on the landscape-the surface features of the Earth, and therefore geomorphological investigations are most easy to carry out based on such data. Through different bands combinations, different lithology and eruption periods of lavas can be highlighted. Remote sensing investigations have a two-fold purpose: (a) to view the ground features in a different perspective, on a different scale, or in a different spectral region, and (b) to reduce the amount of field work involved in covering the entire study area, especially when the target in the region are far away and difficult and expensive to access.
Our approach focus on using remote sensing techniques, supplemented by a literature review and field studies. The approach applied in this study was as follows. Following the introduction, a detailed description of the study area in Saudi Arabia is presented in Sect. 2. In Sect. 3, the methodology to interpret the geological and geomorphological features of AMVF by using multi-source satellite images and the results are described in Sect. 4. In Sect. 5, we discuss AMVF fits the criteria for consideration as a potential volcanic Geopark Project. The conclusions are drawn in the last section.