The Minoan eruption of Thera, also referred to as the Thera eruption or Santorini eruption, was a major catastrophic volcanic eruption with a Volcanic Explosivity Index (VEI) of 6 or 7 and a Dense-rock equivalent (DRE) of 60 km3 (14 cu mi), which is estimated to have occurred in the mid second millennium BC. The eruption was one of the largest volcanic events on Earth in recorded history. The eruption devastated the island of Thera (also called Santorini), including the Minoan settlement at Akrotiri, as well as communities and agricultural areas on nearby islands and on the coast of Crete.
There are no clear ancient records of the eruption; the eruption seems to have inspired certain Greek myths, may have caused turmoil in Egypt, and may be alluded to in a Chinese chronicle. Additionally, it has been speculated that the Minoan eruption and the destruction of the city at Akrotiri provided the basis for or otherwise inspired Plato’s story of Atlantis.
Geological evidence shows the Thera volcano erupted numerous times over several hundred thousand years before the Minoan eruption. In a repeating process, the volcano would violently erupt, then eventually collapse into a roughly circular seawater-filled caldera, with numerous small islands forming the circle. The caldera would slowly refill with magma, building a new volcano, which erupted and then collapsed in an ongoing cyclical process.
Immediately prior to the Minoan eruption, the walls of the caldera formed a nearly continuous ring of islands with the only entrance lying between Thera and the tiny island of Aspronisi. This cataclysmic eruption was centred on a small island just north of the existing island of Nea Kameni in the centre of the then-existing caldera. The northern part of the caldera was refilled by the volcanic ash and lava, then collapsed again.
The radiocarbon dates have significant implications for the accepted chronology of Eastern Mediterranean cultures. The Minoan eruption is a key marker for the Bronze Age archaeology of the Eastern Mediterranean world. It provides a fixed point for aligning the entire chronology of the second millennium BC in the Aegean, because evidence of the eruption is found throughout the region. Despite this evidence, the exact date of the eruption has been difficult to determine. For most of the twentieth century, archaeologists placed it at approximately 1500 BC, but this date appeared to be too young as radiocarbon dating analysis of an olive tree buried beneath a lava flow from the volcano indicate that the eruption occurred between 1627 BC and 1600 BC with a 95% degree of probability.
The eruption devastated the nearby Minoan settlement at Akrotiri on Santorini, which was entombed in a layer of pumice. It is believed that the eruption also severely affected the Minoan population on Crete, although the extent of the impact is debated. Early theories proposed that ashfall from Thera on the eastern half of Crete choked off plant life, causing starvation of the local population. However, after more thorough field examinations, this theory has lost credibility, as it has been determined that no more than 5 mm (0.20 in) of ash fell anywhere on Crete. Other theories have been proposed based on archaeological evidence found on Crete indicating that a tsunami, likely associated with the eruption, impacted the coastal areas of Crete and may have severely devastated the Minoan coastal settlements. A more recent theory is that much of the damage done to Minoan sites resulted from a large earthquake that preceded the Thera Eruption.
Significant Minoan remains have been found above the Late Minoan I era Thera ash layer and tsunami level, and it is unclear whether these effects were enough to trigger the downfall of the Minoan civilization. The Mycenaean conquest of the Minoans occurred in Late Minoan II period, not many years after the eruption, and many archaeologists speculate that the eruption induced a crisis in Minoan civilization, which allowed the Mycenaeans to conquer them easily.
A volcanic winter from an eruption in the late 17th century BC has been claimed by some researchers to correlate with entries in Chinese records documenting the collapse of the Xia dynasty in China. According to the Bamboo Annals, the collapse of the dynasty and the rise of the Shang dynasty, approximately dated to 1618 BC, were accompanied by “‘yellow fog, a dim sun, then three suns, frost in July, famine, and the withering of all five cereals”.
There are no surviving Egyptian records of the eruption, and the absence of such records is sometimes attributed to the general disorder in Egypt around the Second Intermediate Period.
Heavy rainstorms which devastated much of Egypt, and were described on the Tempest Stele of Ahmose I, have been attributed to short-term climatic changes caused by the Theran eruption.
While it has been argued that the damage from this storm may have been caused by an earthquake following the Thera Eruption, it has also been suggested that it was caused during a war with the Hyksos, and the storm reference is merely a metaphor for chaos, upon which the Pharaoh was attempting to impose order.
There is a consensus that Egypt, being far away from areas of significant seismic activity, would not be significantly affected by an earthquake in the Aegean. Furthermore, other documents, such as Hatshepsut’s Speos Artemidos, depict similar storms, but are clearly speaking figuratively, not literally. Research indicates that this particular stele is just another reference to the Pharaoh’s overcoming the powers of chaos and darkness.
The eruption of Thera and volcanic fallout may have inspired the myths of the Titanomachy in Hesiod’s Theogony. The Titanomachy could have picked up elements of western Anatolian folk memory as the tale spread westward. Hesiod’s lines have been compared with volcanic activity, citing Zeus’s thunderbolts as volcanic lightning, the boiling earth and sea as a breach of the magma chamber, immense flame and heat as evidence of phreatic explosions, among many other descriptions.