Historical accounts of the 1650 AD eruption were compiled by Ferdinand A. Fouqué in the 1879 publication Santorini et ses eruptions. Beginning in 1649 AD, Santorini regularly experienced violent earthquakes, worsening in March 1650 AD. The earthquakes were correlated to activity at Kolumbo on 27 September 1650 AD when shaking was accompanied by “clouds of dense smoke and flame[s]” rising from the sea. A subaerial edifice formed from which incandescence and flames were regularly observed. 

Eruption columns repeatedly grew, “blotting out the entire sky”, and collapsed. Eruption column collapse likely would have caused pyroclastic flows and surges that traveled over the sea surface. Modern analogues like Krakatau in 1883, show that the surges flowing over the sea surface present a life-threatening hazard for nearby communities. 

Continuing for four months, earthquakes, sky-darkening eruption columns, toxic gas clouds, pumice rafts, and tsunamis characterized the eruptive activity. Hundreds of heads of cattle and ~70 people perished on Santorini as a result of toxic gases. The eruption culminated on 7 December 1650 AD, but signs of high temperatures in the crater area and weak earthquakes lasted for several years.  

Τhe first phase of the eruption was almost completely submarine, driven by primary degassing that generated stable submarine eruption columns, and resulted in laterally continuous, well-sorted fallout deposits with some interbedded pyroclastic gravity flow units. A second phase was dominated by deposition from numerous sustained hybrid submarine/subaerial plumes in which fallout choked the water column and produced numerous lateral and vertical density currents. 

The Kolumbo volcano is a submarine volcanic environment with high probability for magmatic and tectonic activities, and consequent natural hazards (lava flows to tephra flows, pyroclastic flows, landslides, magmatic degassing, hydrothermal eruptions with potential release of toxic metals, earthquakes, tsunamis). The volcano exhibits extreme environments (vertical inner crater walls, high temperature hydrothermal vent field, CO2 degassing and acidic conditions within the crater, unstructured natural obstacles) and poses a potential ocean acidification hazard as a result of the build-up of hydrothermally emitted CO2 in the crater. Around the submarine volcano sulfide–sulfate hydrothermal chimneys and mounds at 500m depth, provide habitats for microorganisms that are not found or that are only detectable in very low numbers in other marine habitats within an active vent field.

At present, critically active shallow submarine volcanoes near highly populated areas (such as Kolumbo) are only monitored sporadically. SANTORY will address this deficiency by establishing a first–of–its–kind comprehensive seafloor observatory using autonomous instruments to monitor key parameters of hydrothermal and volcanic/seismic activity (e.g. temperature, seafloor deformation and CO2 degassing) and for the first time ever establish reference monitoring protocols in the sense of combining active volcano measurements with Santorini’s on-land data (e.g. seismic, geodetic, geochemical), thus providing the necessary impetus for developing novel risk assessment mechanisms.

Fouqué, F.A., 1879. Santorini and Its Eruptions (translated and annotated by A.R. McBirney, 1998). Johns Hopkins University Press, Baltimore, MD.

Fuller S., Carey S., Nomikou P. (2018). Distribution of fine-grained tephra from the 1650 CE submarine eruption of Kolumbo volcano, Greece. Journal of Volcanology and Geothermal Research 352, pp.10