As one of the hundreds of thousands whose travel plans were scuppered by Icelandic volcano ash, I thought I’d make this post before making the most of what was left of my holiday (curse you, unpronounceable Icelandic volcano!).

Etna erupting in 2001

Long before the recorded eruptions of Eyjafjallajökull, Krakatoa, Etna, Vesuvius, and sundry other volcanoes that have caused chaos, destruction, and provided fertile soil for really good wine, there was the mother of all historic eruptions on the Cycladic island of Thera (Santorini).

The island of Thera today

Located at the south-east of the Hellenic arc (a less volatile version of the Pacific ‘Ring of Fire’) that starts at Kameino Vouno on the Peloponnese, Thera was, until the first part of the Mediterranean Late Bronze Age (beginning c.1600 BCE), an island of roughly circular shape. During the Late Cycladic I (c.1600-1500 BCE) period, Thera had a thriving population with strong cultural and trade links to the Minoan civilisation on Crete, which lies 70-odd miles to the south.

The exact date of the eruption is still contested (see below), but the magnitude of the event is fairly certain. Following a series of earthquakes over a two-year period, the volcano erupted, sending a rain of pumice up to five metres thick to cover the island. This initial explosion was followed by a plume of ash around 30km high when the side of the volcano exploded outwards as seawater mixed with the magma. Rocks were hurled out of the volcano and acted as ‘bombs’, destroying buildings. Surges of ash, pumice, and stone blocks were expelled laterally over the weeks following the first eruption, causing the volcano to collapse in upon itself to leave the distinctive half moon-shaped island we see today.

The eruption triggered a tsunami of an estimated 35-150m height that smashed into northern Crete, variously affecting several of the palace sites. Ash and pumice from the eruption have been found across the Aegean region and into south-western parts of Turkey. Prevailing winds blew the ash cloud to the south-east, though the heaviest ash-fall on land is to be found slightly to the north/north-east of Thera. A large wodge of tephra dating from the eruption has been found outside the Straits of Kythera (the area between the southern Peloponnese and westernmost Crete), dumped there by the currents running through the central Aegean.

On the Volcanic Explosivity Index, the Theran eruption is estimated at a 6-7 (on a scale up to 8). It threw out four times the amount of rock and ash as Krakatoa’s eruption in 1883. In comparison, Eyjafjallajökull’s recent eruption registered at a piffling 4.

The volcanic island Nea Kameni in the Theran caldera erupting in 1950

Specifying the exact date of anything during the Mediterranean Bronze Age is troublesome to say the least, relying in the main on the relative chronology of the Minoan, Helladic (mainland Greece), Cycladic, Cypriot, and Caananite civilisations, all of which overlap to varying degrees (e.g. most of the Late Minoan II-IIIa covers the same chronological phase as Late Cycladic III).

Based on relative chronology, archaeologists suggested a date for the Theran eruption of LMIa/LCI/LHI —around 1500 BCE. This was contested by scientific study of tree-ring dating and radiocarbon analysis. As evidenced by samples taken from North America and across Europe, normal tree growth was stunted in around 1628 BCE due to climactic change, a result of the colder temperatures that usually follow a major volcanic eruption. Carbon dating on wood, seed, and bone samples from the Aegean, including an olive tree buried beneath the lava flow on Thera, point to a date between 1627-1600 BCE with a 95% probability of accuracy.

However, as with almost everything in the field of archaeology, this is not certain and opens up a whole new can of worms as the scientific date contradicts archaeological findings that place several Egyptian artefacts discovered on Thera to a later period. Egyptian chronology is reckoned as being generally sound, though arguments have been made for its dates to be reassigned. If the radiocarbon dating is correct, the chronology for the Mediterranean Bronze Age would need to be reassessed.

The town of Oia, perched high on the caldera cliffs

The Theran eruption obliterated the Bronze Age settlements on the island, including the ‘town’ of Akrotiri, seemingly the centre of Minoan influence within the southern Cyclades. Most inhabitants of Akrotiri (and presumably the rest of the islanders) had fled following a massive earthquake that partially demolished the settlement. There is evidence that some people returned to Akrotiri as squatters (no real effort was made to rebuild the damaged properties), but by the time of the eruption, the majority of the inhabitants had left the island.

The layers of ash and pumice that covered Thera effectively killed off every living thing, turning the island into a barren wasteland. Thera remained uninhabited for almost 300 years.

Across the sea in Crete, the effect of the eruption is another hotly debated point. Originally, prehistorians believed that ash-fall blighted the eastern half of Crete, causing crop failure and starting a migration of the population. However, the actual ash-fall on Crete has since been found to be insignificant. Another theory is that the tsunami was the cause of the destruction of the Minoan sites and palaces on the northern (especially the north-eastern) coast of Crete, many of which suffered extensive fire damage. Stone walls at some sites were moved by the force of the tsunami, but it’s unlikely that the wave caused the wholesale destruction found across Crete—instead, it’s probable that the damage was due to the massive earthquake preceding the eruption.

Regardless of the physical destruction that may or may not have been wreaked by the volcano, the psychological effect must have been far more devastating. Minoan power was waning during the Late Bronze Age, and as the Minoans were a major sea power at that time, it’s likely that many of their ships, naval and mercantile, were destroyed in the aftermath of the eruption. It’s believed that the Theran eruption provided the impetus for the newly emerging Mycenaean civilisation to expand southwards. Certainly by LMII (1450-1400 BCE), the Mycenaeans had conquered the Minoans and held control of Crete.

Of course, one can’t talk about Thera without mentioning Atlantis. For millennia, people have discussed whether or not this island kingdom, mentioned by Plato in his dialogues Timaeus and Critias (written in 360 BC), actually existed. Some of Plato’s successors believed Atlantis was a real place; others thought it was allegorical. The same debate continues today, with many people believing that Atlantis is/was Thera or Crete.

Atlantis is described as an island ‘larger than Libya and Asia’ (Asia being what is today Turkey) amongst other islands, surrounded by an ocean and ruled by a confederation of kings—a description that (apart from the size!) matches the Minoan civilisation. According to Critias, his account of Atlantis originated with the sixth century BC lawgiver Solon, who visited Egypt and heard the tale from a priest. The empire of Atlantis, Critias says, flourished 9000 years ago (i.e. 9600 BCE) before coming to a messy end:

But at a later time there occurred portentous earthquakes and floods, and one grievous day and night befell them, when the whole body of your warriors was swallowed up by the earth, and the island of Atlantis in like manner was swallowed up by the sea and vanished; also the ocean at that spot has now become impassable and unsearchable, blocked up by the mud which the island created as it settled down.

It is entirely possible that the Theran eruption and the destruction of the Minoan civilisation was preserved as a folk memory and passed down through the centuries until Plato recorded it in this form as the myth of Atlantis.