An explosive eruption
Around 1600 BCE, the island of Thera, now known as Santorini, experienced one of the most powerful volcanic eruptions in human history. Modern volcanologists classify this event as a 7 on the Volcanic Explosivity Index (VEI), a logarithmic scale where each interval represents a tenfold increase in eruptive power. The eruption ejected an estimated 28 to 41 cubic kilometers of material as dense-rock equivalent. This volume is several times greater than the 1883 eruption of Krakatoa.
The eruption occurred in several phases. An initial Plinian phase sent a column of ash and pumice 30 to 35 kilometers into the stratosphere. This was followed by phreatomagmatic explosions, which occur when hot magma violently interacts with seawater. Over the course of the eruption, the magma chamber beneath the island emptied, causing the center of the volcano to collapse and form the large sea-filled basin, or caldera, that defines Santorini's geography today. Ash from this event is an important marker horizon for archaeologists, found in sediments across the eastern Mediterranean and Turkey. Radiocarbon dating of organic material buried by the ash places the event between 1627 and 1600 BCE.
The tsunami trigger
The collapse of the Theran volcano generated a massive tsunami with waves estimated to be 35 to 150 meters high near the source. For decades, scientists believed the primary trigger was the caldera collapse itself displacing a huge volume of water. However, recent bathymetric and seismic evidence suggests a different primary mechanism. It appears the caldera was initially isolated from the open sea by volcanic deposits from the early stages of the eruption.
The current scientific consensus points to massive pyroclastic flows as the main cause of the tsunami. These are superheated, fast-moving currents of gas, ash, and rock. As enormous volumes of this material flowed from the volcano directly into the Aegean Sea, they displaced enough water to create the enormous waves. The subsequent collapse of unstable submarine deposits of this pyroclastic material also contributed to the tsunami's power. This model is similar to the mechanism that generated the deadly tsunami during the 1883 Krakatoa eruption. Once the eruption ceased, the sea breached the new caldera walls, flooding the basin in less than two days.
Evidence on crete
The tsunami had a devastating impact on the northern coast of Minoan Crete, located about 110 kilometers south of Santorini. At the archaeological site of Palaikastro, researchers have found extensive evidence of the tsunami's impact. The deposits contain a chaotic mix of building materials, pottery, marine shells, and volcanic pumice from Thera. The presence of deep-sea microfossils mixed with coastal debris indicates a powerful wave transported material from different marine environments onshore. At Amnisos, another Minoan coastal town, building walls were found knocked out of alignment. The tsunami deposits provide a direct physical link between the eruption and widespread destruction on Crete, showing that the event was a major factor in the subsequent decline of the Minoan civilization's maritime power.