Santorini volcano: Freak eruption 1,300 years ago was as violent as 2022 Tonga eruption

An eruption at Santorini volcano 1,300 years ago was far more violent than previously thought, suggesting explosive blasts can occur even in periods of relative quiet, new research shows.

Santorini is an underwater volcano located along a string of volcanoes known as the Hellenic Island Arc between Greece and Turkey. It can produce eruptions that are so large the crust above the magma chamber collapses and forms a bowl-shaped pit, or caldera, several miles across. The last caldera-forming eruption at Santorini, known as the Minoan eruption, occurred in 1600 B.C. and blew the top off what was then one island, leaving behind the present-day archipelago. 

Eruptions of this scale are typically followed by a "rejuvenation" period, during which the magma chamber replenishes and feeds only small eruptions. But a huge explosion in the year A.D. 726 has scientists rethinking how the volcano behaves during quiet periods, according to a study published Monday (March 25) in the journal Nature Geoscience. 

"Historical accounts mention that, during the summer of 726 C.E., the sea within the Santorini caldera began to boil until dense smoke rose and was accompanied by pyroclastic eruptions," researchers wrote in the study. (Pyroclastic eruptions are characterized by flows of blistering ash, gas and rock.) "Large pumice blocks were ejected in such quantity that they covered the sea over an immense area, reaching the coasts of Macedonia and Asia Minor more than 400 km [kilometers, or 250 miles] away."

Related: Underwater Santorini volcano eruption 520,000 years ago was 15 times bigger than record-breaking Tonga eruption

While these descriptions hint at a violent explosion, the only trace of this eruption previously found was a thin layer of pumice on Palea Kameni — one of two islands that sit in the center of the Santorini caldera, where a vent called the Kameni volcano opened up following the Minoan eruption.

Now, scientists have gleaned the full extent of the 726 eruption and found that it likely blasted from the Kameni vent with a magnitude similar to that of the record-shattering Tonga volcano eruption of 2022, according to the study.