An underwater eruption of the Santorini volcano, which occurred in 726 AD. and it was much larger than the scientific community believed until today, researches of an international oceanographic mission brought to light.

The results were published in the journal Nature Geoscience.

Scientific research – For the first time underwater drilling at a depth of up to 160 meters inside the caldera

The scientists who participated in the oceanographic research mission 398 in Santorini, within the framework of the “International Ocean Discovery Program”, led by Jonas Prine from the University of Hamburg and the participation of the associate professor of the Department of Geology and Geoenvironment of the EKPA, Evie Nomikou, carried out for the first time underwater drilling at a depth of up to 160 meters inside the caldera of Santorini and discovered underwater pumice deposits which are placed in time the 726 AD and are consistent with historical records of an underwater explosion occurring at that time.

Although this explosion was known, it was considered very small until today. But as the research team found, it produced such a large quantity of pumice that it covered the sea over a vast area as far as the coast of Asia Minor, i.e. more than 400 kilometers away.

The JOIDES research vessel in the Santorini caldera, with the Nea Kameni volcano in the background. Credit: Thomas Ronge, JRSO IODP.

This violent explosion must have occurred mostly under the surface of the water, as no remains of it have been found on land. The volume of this layer of ash and rock can be up to 3.1 cubic kilometers with an estimated explosion magnitude (VEI) of five.

The volcano is in a “recharge” phase, after the Bronze Age eruption

THE Santorini is active for about 650,000 years and is classified as a polycyclic volcanowith renewal and recharge phases through new magma flows with small but frequent eruptions.

This is followed by a build-up phase with few eruptions over many thousands of years before a powerful eruption that causes the caldera to collapse, the last being the Minoan eruption that occurred in the Bronze Age, around 1,600 BC. After this massive eruption, a new volcano, Kameni, appeared in the center of the caldera, and today the peaks of this mostly submarine volcano form the islands of Nea and Palaia Kameni within the Santorini caldera.

The recent findings of Expedition 398, involving 32 scientists from nine countries, challenge the prevailing knowledge of Santorini’s volcanic phases. As the volcano is located in a typical phase of lava formation (recharge) after the explosion of the Bronze Age, scientists until today considered that this phase is capable of producing small explosions. However, recent underwater drilling and the discovery of a 40-meter-thick pumice layer show that the volcano was capable of not only small eruptions, but also larger ones during the early stages of the caldera cycle.

It is noteworthy that the eruption of 726 AD was 30 times smaller than the Minoan and “there is no indication that such an eruption will occur again in the near futuren”, as Ms. Nomikou explains to APE-MPE. However, he underlines that “the change in understanding of the behavior of the Santorini volcano has important implications for volcanic hazard assessment and must be taken into account in volcanic hazard assessments and evaluation.”

As she adds, these findings “also show that the global record of volcanic eruptions is largely deficient in subsea eruptions. The recognition of potentially dangerous eruptions in the early stages of the caldera construction cycle is crucial for the development of comprehensive risk reduction strategies both locally and globally.”