Seafloor hydrothermalism linked to arc and MOR volcanoes connects deep-seated mantle processes to the chemical and biogeochemical evolution of the global oceans, and supports geochemical–thermal exchanges that sustain an astonishing diversity of seafloor vent ecosystems influencing the carbon cycle globally. Moreover, submarine volcanism produces mineral deposits of major economic potential. Practically, 65% of all known modern seafloor hydrothermal systems with their associated mineral deposits and chemosynthetic microbial biomes, occur at intermediate (and slow) MORs and mature back–arc spreading centers, typically at water depths of 2.000 to 4.000m. The less studied seafloor hydrothermal vent sites are associated with shallow submarine arc volcanoes and arc–related rifts in subduction–related settings, and typically occur at a water depth <500m.

The necessity to understand the highly dynamic nature of submarine hydrothermal systems as they evolve and affect submarine processes and volcanic activity has led to the first attempts of developing in situ Seafloor Observatories. To this end, the Azores node of EMSO (http://emso.eu/) and the Canada/US cabled observatories (https://www.oceannetworks.ca/, https://oceanobservatories.org/array/cabled-axial-seamount-array/) were developed to identify and record, at high resolution, the change of their dynamics and evolution to basin floor and explosive submarine volcanism. However, due to the remoteness of these deep ocean observatories from populated areas, their recorded data cannot be used to directly address the hazard in small ocean basins, such as the Mediterranean, where very few active submarine volcanoes like Kolumbo, are proximal to densely populated areas (i.e. Santorini volcanic island). In order to fill this gap, SANTORY focuses on developing and integrating SoA, innovative technology, coupled with well–tested instrumentation in deep–sea exploration, to monitor active shallow (<500 m) hydrothermal vent field processes and assess volcanic hazards.