Long thought to be based on historical accounts, the underwater volcanic eruption that is said to have triggered the iconoclastic period in the Byzantine Empire in the year 726 did indeed occur. A recent campaign on the Santorini caldera provides evidence of this event and reveals that this volcano may have a more unpredictable behavior than previously thought.
Although Santorini is primarily known for its devastating eruption 3,600 years ago, which led to the collapse of the Minoan civilization, recent studies reveal that this volcanic complex has violently erupted multiple times over the past millennia.
A volcanic cycle that ends each time with the formation of a caldera
Studying past eruptions suggests that, like many large volcanic systems, Santorini follows cycles where there is first a phase of magma recharge marked by constructionconstruction of volcanic structures through small and frequent eruptions, followed by a system maturation phase where eruptions become less frequent but more powerful, culminating in a major explosion leading to a collapsecollapse of the magma chamber and the formation of a calderacaldera.
Each cycle could last tens of thousands of years. Currently, Santorini is in its magma accumulation phase, indicating that a major eruption is still far off.
Historical accounts pointing to a violent eruption in 726
However, the first phase of this cycle may not be as calm as previously thought. This is revealed by the results of an oceanographic campaign (IODP 398). These results suggest a violent underwater eruptionunderwater eruption occurred in the year 726. These observations align with historical accounts describing a “seething of the sea,” massive arrival of “floating rocks” on the coasts of Asia Minor and Macedonia, and the formation of a new island in the Aegean Sea. This phenomenon was interpreted by Emperor Leo III of Constantinople as a divine wrath manifestation against the worship of iconsicons. To appease his god’s anger, the Byzantine emperor ordered the destruction of all images depicting holy figures.
This iconoclasm had significant repercussions in Byzantine society, leading to strong instability in the Empire. While the accounts are detailed, until now, no scientific evidence had confirmed this eruptive event. The latest scientific campaign has provided evidence with the discovery of a 40-meter-thick layer of ash and pumice stones at the bottom of the sea.
A more unpredictable volcanic behavior than anticipated
These new findings, published in the journal Nature Geoscience, reveal that even in its relatively calm magma accumulation phase, Santorini is capable of producing powerful explosions. These data help better assess the eruptive potential and danger of this volcanic system.