The Thera Eruption; An event that changed the ancient world

Ron Current
Ron Current

The volcanic eruption of Thera is also known as the Santorini Eruption or the Minoan Eruption. It was this historic event that made stopping at Santorini one of the most anticipated of my Greece trip. What really got me excited when I read about Thera’s eruption was the magnitude of it, and how it affected history, may have been a part of a biblical story and could have also created a famous myth.

As I stood at the edge of the crater, looking down at the sea filled caldera, I tried to picture what it may have looked like before the historic eruption. Geological studies have shown that it looked very much as it does today.

Santorini map
The Archipelago of Santorini. The ring of the ancient volcano can be seen.

The caldera, as today, was filled by the sea. However instead of five islands ringing the caldera it was nearly one continuous landmass then. There was one small opening at the south end of the ring, the only entrance into the inter harbor. That opening would have been between today’s Thera and Aspronisi islands. At the center of the caldera, as today, would have been a smoldering island volcano that would be the center of the cataclysmic eruption to come. To the Minoans, being people of the sea, they were drawn to the protected harbor, making it a perfect place to build one of their main trading ports.

The Volcano Island of Nea Kameni
The island of Nea Kameni at the center of the caldera. The growing volcano that will be the site of the future eruption.

It is believed that the Thera volcano had erupted many times over the several hundred thousand years before the Bronze Age event.  It had repeated the process of building a volcano, then a violent eruption with the island collapsing into a rough circle and the sea filling the caldera. But the Minoans were unaware of this process due to the fact that there were centuries between each of these events.

At around 1627 and 1600 BC the new volcano at center of the caldera became active. First there were earthquakes. This made the residences of the island aware that something was happening. Studies suggest that there were four phases to the eruption after the earthquakes began. The first was a thin expulsion of ash. This preliminary activity most likely gave the population a few months to flee the island. This could be one of the reasons why there no human remains or valuables found at the buried city of Akrotiri. But did the Minoans flee far enough to save themselves? And what effect did the final eruption have on the Minoan civilization and that of the whole region.

A Minoan vase from Akrotiri

So how big was the final eruption? To gage the size of a volcanic eruption volcanologist use what is called a Volcanic Exclusivity Index, or VEI. Using this index the Thera eruption is believed to have been a 7.  So how does Thera’s compare to other famous known eruptions? Mt. Vesuvius in 79 AD, that buried Pompeii, is figured to have been at a 5, Mt. St. Helens in 1980 at a 4, and the famous 1883 eruption of Krakatoa is rated at a 6. An VEI rating of 7 makes the Thera event one of the largest in history.

The total volume of ejected material is estimated at approximately 24 cu mi, projecting an ash plume up to 22 miles into the stratosphere. The final explosion generated a mega-tsunamis that is thought to have reached a height from 115 to 492 feet, washing over the coasts and islands of the eastern Mediterranean. The Thera eruption would have also affected the climate of the entire northern hemisphere for years after.

The famous “Blue Monkeys” fresco from Akrotiri.

This super eruption has been theorized to have played a part in the Hebrew Exodus from Egypt, as helping to cause the plaques and the parting of the sea.  It is also believed to have led to the collapse of the Minoan civilization, which ended at around 1400 BC. There is no way that the centers of that civilization could have withstood the destruction that would have been caused by that eruption. So even if the population of Thera had left before the final blast they would have still been subjected to the aftermath caused by it.

But what really fascinated me about this massive eruption was its provable connection to Plato’s Atlantis!  More on that in a later post!

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