A new study reveals the existence of a large mass of mobile magma under Kolumbo, an active submarine volcano near Santorini (Greece), which until now had not been detected.
The presence of the magma chamber – detected thanks to a novel volcano imaging technique that produces high-resolution images of seismic wave properties – increases the odds of a future eruption, leading researchers to recommend real-time hazard monitoring stations near other active submarine volcanoes to improve estimates of when an eruption is likely to occur.
Nearly four hundred years ago, in 1650, the Kolumbo broke the surface of the sea and erupted, killing 70 people on Santorini. This eruption, which should not be confused with the catastrophic volcanic eruption of Thera (Santorini) that occurred around 1600 BC, was caused by the growth of magma deposits under the surface of Kolumbo. Now, the researchers say that the molten rock in the chamber is reaching a similar volume.
The study, published in the journal Geochemistry, Geophysics and Geosystems, is the first to use full-waveform inversion seismic imaging to look for changes in subsurface magmatic activity at submarine volcanoes in the Hellenic Arc, where Kolumbo is located. .
Full waveform inversion technology is applied to seismic profiles – records of ground motion along kilometer lines – and assesses differences in wave velocities that may indicate subsurface anomalies. The study demonstrated that full waveform inversion technology can be used in volcanic regions to find possible locations, sizes, and melt rates of mobile magma bodies.
The seismic profiles were built after the researchers fired air cannon shots from a research vessel hovering over the volcanic region, causing seismic waves that were recorded by bottom seismometers located along the arc.
“The full waveform inversion is similar to a medical ultrasound,” Michelle Paulatto, a volcanologist at Imperial College London and second author of the study, explains in a statement. “It uses sound waves to build an image of the underground structure of a volcano.”
According to the study, a significant decrease in the speed of seismic waves traveling under the seabed indicates the presence of a mobile magma chamber under Kolumbo. The characteristics of the wave anomalies were used to get a better idea of the potential dangers that the magma chamber can present.
According to Kajetan Chrapkiewicz, a geophysicist at Imperial College London and lead author of the study, existing data on the region’s submarine volcanoes were sparse and fuzzy, but the dense set of seismic profiles and full waveform inversion has enabled them to get much sharper images than before. These were used to identify a large magma chamber that has been growing at an average rate of about 4 million cubic meters per year since the last eruption of Kolumbo in 1650 CE.
According to the study, the total volume of melt accumulated in the magma deposit under the Kolumbo is 1.4 cubic kilometers. According to Chrapkiewicz, if the current growth rate of the magma chamber is maintained, at some point in the next 150 years Kolumbo could reach the 2 cubic kilometers of molten volume estimated to have been ejected during the 1650 CE eruption. While the volumes of volcanic melting can be estimated, there is no way of knowing for sure when Kolumbo will erupt.